[Sky & Telescope magazine in April 2009] Sky & Telescope... -

Robert Naeye Spectrum Founded in 1941 by Charles A. Federer, Jr. and Helen Spence Federer The Essential Magazine of Astronomy E D ITOR IAL Editor in Chief Robert Naeye Changes to S&T Senior Editors Dennis di Cicco, Alan M. MacRobert Associate Editors Tony Flanders, Stuart J. Goldman Imaging Editor Sean Walker The magazine’s metamorphosis has you in mind! Editorial Assistant Katherine L. Curtis Editors Emeritus Richard T. Fienberg, Leif J. Robinson Senior Contributing Editors J. Kelly Beatty, Roger W. Sinnott Contributing Editors Edwin L. Aguirre, Adrian R. Ashford, Greg Bryant, Paul Deans, Thomas A. Dobbins, David W. Dunham, Alan Dyer, Sue French, Paul J. Heafner, Ken Hewitt-White, Johnny Horne, E. C. Krupp, David H. Levy, Jonathan Mc Dowell, David Ratledge, Fred Schaaf, Govert Schilling, If you’re a long-time subscriber, you have probably Gary Seronik, William Sheehan, Charles A. Wood Contributing Photographers P. K. Chen, Akira Fujii, Tony & Daphne Hallas noticed subtle changes over the past few months, and perhaps more with AR T & D E S I GN this issue than any other. My colleagues and I have thought long and hard Design Director Patricia Gillis-Coppola about how to put our pages to their best possible use for you, the reader. The Illustration Director Gregg Dinderman Illustrator Casey Reed gradual evolution you’re seeing is the result of numerous discussions held PUBL ISH I N G over many months. VP / Publishing Director Joel Toner When I assumed the helm as editor last June, I wanted to give the maga- Advertising Sales Director Peter D. Hardy, Jr. zine more fl exibility so we could expand our coverage of important areas Advertising Services Manager Lester J. Stockman such as astrophotography, deep-sky observing, and amateur contributions to VP, Production & Technology Derek W. Corson Production Coordinator Michael J. Rueckwald science. When I discussed my ideas with my editorial and art colleagues, we Ad Production Coordinator Kristin N. Beaudoin reached a consensus that we needed to free up space so we could run articles IT Manager Denise Donnarumma on a wider variety of topics, by a wider variety of authors. S&T subscribers VP, Consumer Marketing Dennis O’Brien Director of E-Media Stephen Singer expressed similar sentiments when I asked them about the magazine. Fulfi llment & Renewals Manager Dominic M. Taormina Over the past few months, we’ve given ourselves fl exibility by reducing New Business Manager Adrienne Roma Marketing Coordinator Kim Ciommo-LeBlanc pages devoted to regular departments, and devoting more to features. We Credit Manager Beatrice Kastner have brought in a new voice (David Grinspoon), while retaining our famil- NE W T R AC K ME D I A L L C iar voices (Sue French, Ken Hewitt-White, Fred Schaaf, Gary Seronik, and Chief Executive Offi cer Stephen J. Kent Executive Vice President / CFO Mark F. Arnett Chuck Wood) whose articles speak directly to the needs of amateur astrono- Corporate Controller Jordan Bohrer mers. Ken will start a new column next month: “Going Deep.” We’ve rear- Offi ce Administrator Laura Riggs ranged some of our observing material to give it a more logical order. Editorial Correspondence: Sky & Telescope, 90 Sherman St., Cambridge, MA 02140-3264, USA. Phone: 617-864-7360. Fax: 617-864-6117. E-mail: Since we have a fi nite number of pages in each issue, we had to make [email protected]. Website: SkyandTelescope.com. Unsolicited room for new stuff by dropping some of our regular departments. Several proposals, manuscripts, photographs, and electronic images are welcome, but a stamped, self-addressed envelope must be provided to guarantee their former columnists will now be contributing by writing occasional feature return; see our guide lines for contributors at SkyandTelescope.com. articles. I’m also very pleased to announce that David Levy has started a new Advertising Information: Peter D. Hardy, Jr., 617-864-7360, ext. 2133. blog on SkyandTelescope.com titled “On the Road with David Levy.” He’s Fax: 617-864-6117. E-mail: [email protected] posting new entries weekly, so please check it out! Web: SkyandTelescope.com/advertising All of these changes are designed to bring in fresh content, voices, and Customer Service: Subscription inquiries and change-of-address notices: [email protected] perspectives — to make the magazine more representative of all the incred- Phone toll free: 800-253-0245. Outside the US and Canada: 386-597-4277. ible stuff going on in the world of amateur astronomy. We’re adapting to Product inquiries: [email protected] Phone toll free: 888-253-0230. changing circumstances and a challenging economic environment while BIGSTOCKPHOTO.COM, CATERPILLAR: GOODOLGA / BUTTERFLY: SPANISH ALEX without written permission from the publisher. For permission to make multiple maintaining the qualities that have made S&T dear to the hearts of so many Subscription Rates: US and possessions: $42.95 per year (12 issues); Canada: $49.95 (including GST); all other countries: $61.95, by expedited readers for so many years. Please let us know what you think! delivery. All prices are in US dollars. Finally, I would be remiss in my duties if I didn’t mention 100 Hours of Newsstand and Retail Distribution: Curtis Circulation Co., Astronomy, which takes place April 2–5. As Mike Simmons explains in his 730 River Rd., New Milford, NJ 07646-3048, USA. Phone: 201-634-7400. article (page 72), a global star party will sweep around the world. It’s the per- No part of this publication may be reproduced by any mechanical, photographic, fect time for amateurs to strut our stuff and attract newcomers to our fi eld! or electronic process, nor may it be stored in a retrieval system, transmitted, or otherwise copied (with the exception of one-time, noncommercial, personal use) photocopies of the same page or pages, contact the Copyright Clearance Center, 222 Rosewood Dr., Danvers, MA 01923, USA. Phone: 978-750-8400. Fax: 978-750-4470 Web: www.copyright.com. Specify ISSN 0037-6604. Sky & Telescope and logo, Sky and Telescope, The Essential Magazine of Astronomy, Editor in Chief The following are registered trademarks of Sky & Telescope Media, LLC: Skyline, Sky Publications, SkyandTelescope.com, http://www.skypub.com/, SkyWatch, Scanning the Skies, Night Sky, and ESSCO. 8 April 2009 sky & telescope © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Letters Before Galileo INSTANT 3-D Merge this pair of images I’m disappointed to see Sky & Telescope per- from ESA’s Rosetta space- petuating the myth that telescopic astron- craft into a single view and omy began with Galileo. An Englishman, you’ll see asteroid 2867 Thomas Harriot, was using the instrument Steins with new depth. ESA / OSIRIS TEAM at least four months earlier, in July 1609, to view the Moon from the grounds of a stately home just west of London. He later Depth Perception Lights Out! produced a remarkably fi ne Moon map. He also made careful observations of the satel- Sky & Telescope readers who glanced over The December issue’s News Note “Low- lites of Jupiter and sunspots. the News Note on the Rosetta spacecraft’s Polluting Streetlights” (page 18) implies You can read more about him on my encounter with the asteroid 2867 Steins that diodes and fi xtures will reduce light blog at http://tinyurl.com/harriot. (December issue, page 15) may not have pollution. No way! Until we roll back realized that the images can be easily urban sprawl and start turning lights off , Paul Sutherland used to produce a three-dimensional view. light pollution will continue to grow. And London, UK Without any optical aid, you can merge as Alan MacRobert pointed out in the [email protected] the two rightmost complete images (see November issue (page 91), broadband light above) by staring at them and refocusing pollution has defeated our fi lters. Editor’s Note: Harriot (and others) may have your eyes so that each eye concentrates Bob Guzauskas pointed a telescope skyward before Galileo, on only one of the pictures. The result is West Palm Beach, FL but they didn’t publish their observations and indeed a surprise! The asteroid doesn’t [email protected] analysis for other scientists, so they didn’t really have the apparent “diamond” shape have any signifi cant impact. Galileo still at all. Try it and see. deserves credit for getting telescopic astron- Alex Heydon Write to Letters to the Editor, Sky & Telescope, omy going. He was the one who made a big Ajax, ON 90 Sherman St., Cambridge, MA 02140-3264, or send e-mail to [email protected]. deal of it and made the world take notice. [email protected] 75, 50 & 25 Years Ago Leif J. Robinson April 1934 rare. On the other hand, the another 15 percent plan to purchase one. . . . Planetarium Debut “The fi rst planetarium in short-period objects domi- “The new monthly department, called Astro- the western hemisphere was opened to the nate the distribution in the nomical Computing, begins in this issue. It is a public on May 12, 1930. Situated on a man-made direction of the anticenter, forum for exchanging small programs, hardware island in Lake Michigan off with the most frequent hints, and accounts of fascinating things that Grant Park in Chicago, it forms period being only four days. are already being done astronomically with a fi tting compliment to the The distribution in the Cyg- home computers.” Field Museum of Natural His- nus and Carina directions is The fi rst installment featured a test of a tory and the Shedd Aquarium, intermediate between those of the center and Radio Shack TRS-80 Model I (with 4 kilobytes its two nearest neighbors. . . . anticenter directions.” of memory when introduced in 1977 and later In June of 1933 the new Sidney van den Bergh’s study involved all upgraded to 16KB), which was used to compute Lower Floor Museum Hall Cepheid variable stars known before 1956 that ephemeredes for Jupiter through Pluto from 1653 was opened. . . .” were fainter than magnitude 11.0 and within 10° to 2060. The results (coordinates to nine decimal of the galactic equator. places) essentially matched April 1959 those obtained with IBM’s Sorting Cepheids “Almost all the distant April 1984 Selective Sequence Elec- Cepheids in the direction of the [Milky Way’s] Computer Invasion “Computers are changing tronic Calculator, which center have periods longer than 10 days, with the tenor and tempo of amateur astronomy. For performed the calculation many about 15 days, while Cepheids with example, 32 percent of this magazine’s readers in 1950 and was the only periods between two and eight days are quite own some kind of personal computer, and computer that could. 10 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Letters Cosmic Fictionalization? do multiverses make testable predictions? Galileo’s words from your February 2009 How do multiverses diff er from science article “The Moon, the Telescope, and the fi ction? When did science begin to posit Birth of the Modern World” (page 28) are metaphysical speculations to shore up its apt. But, sadly, they provide an embarrass- own ignorance? When did it depart from ing commentary on the current ad hoc the scientifi c method in a desperate search “scientifi c method.” to justify its all-knowing powers by any Authors Stephen Maran and Laurence means? And when did it abase its noble Marschall properly state that science is methods so that, by hook or crook, the “the radical idea, quite foreign to human very idea of God would never be tolerated? nature, that an objective reality exists Is it really so scary that scientists must apart from our own internal whims, con- have made-up stories? ceits, and made-up stories.” Ronald S. Bashian, MD Galileo elaborates: “The hypothesis Arlington, VA is pretty; its only fault is that it is neither [email protected] demonstrated nor demonstrable. Who does not see that this is purely arbitrary fi ction that puts nothingness as existing For the Record and proposes nothing more than simple ✹ The photograph of the unnamed nebula noncontradiction?” in Cygnus on page 102 of the December issue Physicist Wolfgang Pauli, more was imaged in collaboration with Mel Helm. recently, labeled such thinking as “nicht The nebula was fi rst noticed by amateur einmal falsch” (“not even wrong”). David Jurasevich, who reported the discovery Fittingly, Galileo’s words and Pauli’s to the International Astronomical Union. critique describe the very fi ction of multi- ✹ The estimated mass of material ejected verses. from Comet 9P/Tempel 1 by the Deep Impact Does the deus ex machina idea of multi- mission was 20,000 tons (January issue, verses merit the term “scientifi c”? Where page 16). ON THE WEB PREPARE FOR STAR-PARTY SEASON SkyandTelescope.com/events WHAT CAN YOU OBSERVE? SkyandTelescope.com/objects GAZING GEAR AND GOODIES SkyandTelescope.com/equipment LIFE WITH LEVY AUDIO TOUR GUIDE BLOGGING THE AMATEUR ANGLE HEAR THE HEAVENS BIGSTOCK.COM / MIKE REMBACZ We welcome long-time S&T columnist Want some celestial accompani- David H. Levy to our ment? Download our monthly website, where he will skygazing podcast, grab your MP3 regularly contribute player, and head outdoors. We’ll news and thoughts about point out all that’s interesting and amateur astronomy — or worthy of your attention in the whatever catches his realm over your head. attention. SkyandTelescope.com/ SkyandTelescope.com/ community/skyblog podcast S&T: RICHARD TRESCH FIENBERG 12 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

News Notes New Cosmic Background Found A team of scientists using a another type of “cosmic background sensitive balloon-borne instrument has radiation” — distant emission coming found an unexplained hiss of relatively from everywhere on the sky — to go low-frequency radio pervading the along with the backgrounds previously universe. The discovery represents yet discovered in microwaves, infrared light, X-rays, and gamma rays. Team leader Alan Kogut (NASA/Goddard Space Flight Center) calls it “exciting evidence for something new in the cosmos.” But no one knows yet what it may be. Kogut and his colleagues built and fl ew an instrument named ARCADE: Absolute Radiometer for Cosmology, Astrophysics, and Diff use Emission, seen at right just before launch. They ARCADE TEAM hoped to detect highly redshifted radio emission from the fi rst generation of stars. Instead, ARCADE found an other, more exotic mechanism for pro- excess of lower-frequency radio waves ducing radio emission in the universe.” (3 to 8 gigahertz) coming from every- In the symbolic illustration at left, where on the 7% of the celestial sphere ARCADE looks back through the Milky it surveyed. Way (starry band) to other galaxies, the “If the result holds up, it is quite cosmic web of distant galaxy clusters, interesting,” says cosmologist Gary the “reionization era” (gray band; one NASA / ARCADE / ROEN KELLY means that radio galaxies, or some comes from there), to the fi rst super- Hinshaw (NASA/Goddard). “It either guess is that the new radio background stars and quasars lighting up at the class of radio galaxies, have diff er- end of the Dark Ages several hundred ent properties than were previously million years after the Big Bang. thought, or perhaps there is some Dark Energy: something like antigravity has increas- for Astrophysics). It turned out that the Real and Overwhelming ingly retarded their evolution as the uni- younger clusters grew to be less massive Something akin to antigravity — it was verse ages. The researchers mapped the than they would have if dark energy had dubbed “dark energy” for lack of a better hot, X-ray-bright gas fi lling doz- not been doing its mysterious term — is infl ating space on the largest ens of clusters — some relatively work. scales and speeding up the expansion of young, others much older— to The new result also nar- the universe. Implausible as it may seem, determine their masses. “A clus- rows the range of uncertainty new evidence keeps coming in. ter’s growth is really a competi- in dark energy’s “equation of Cosmologists recently announced that tion between gravity’s pull and R. HURT / M. REID / NRAO / AUI / NSF state” (its pressure divided by distant clusters of thousands of galaxies the accelerating expansion” of energy density). Apparently — the largest structures in the universe space, explains William Forman the amount of dark energy in held together by gravity — show signs that (Harvard-Smithsonian Center a given volume of space — a 16 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

For astronomy news as it breaks, see or a F Skyan SkyandTelescope.com/newsblog. cubic centimeter, for instance — remains Mission Update Jonathan McDowell the same no matter how greatly space expands. This means that dark energy is somehow associated with empty space itself, rather than being some kind of par- J-MAPS: Next Step will generate an enormous high-precision ticles or fi eld residing in space — which for Astrometry database of stars down to 20th magnitude, would thin out as space expands, as atoms but it will not be able to measure the and galaxies do. The U.S. Naval Observatory is leading brightest stars accessible to J-MAPS. In other words, quips David Spergel a new space mission to measure the In addition, J-MAPS will observe (Princeton University), “Even nothing positions, motions, and distances of tens distant radio-loud quasars as faint as 16th magnitude so that its star positions can weighs something.” And the weight of be matched with radio astronomy’s own nothing has a negative value. highly precise coordinate system. The image at the bottom of the facing The small, 115-kilogram (254-pound) page shows the galaxy cluster Abell 85 satellite will be built by the Naval Research with its diff use, X-ray-hot gas superposed Lab. Its star-position catalog is intended for in purple. military as well as astronomical purposes. The Milky Way USNO / ONR Stardust Revived Doubles its Mass In 2004 NASA’s Stardust spacecraft, J-MAPS will fi ll in gaps between the Hip- orbiting the Sun since 1999, fl ew by Comet Using a network of 10 radio telescopes parcos and future Gaia star catalogs. Wild-2 and collected a tiny cargo of space worldwide, a group has measured dust. In 2006 it sent its sample capsule of millions of stars. The Joint Milli- extremely precise parallaxes (distances) of parachuting to the Utah desert and went Arcsecond Pathfi nder Survey, funded by radio sources in 18 of the Milky Way’s star- into hibernation as it receded into space. the Offi ce of Naval Research, will generate forming regions, as well as their motions In 2007 NASA approved a new mission for a catalog of star positions to fainter than in three dimensions. The study provides a magnitude 12 — a larger, second-epoch the craft: Stardust-NExT, the suffi x standing new map of the galaxy’s rotation indepen- counterpart to Europe’s pioneering for “New Exploration of Tempel.” After dent of most astronomical assumptions. Hipparcos mission launched in 1989. the Deep Impact probe smashed a copper The team fi nds that the Milky Way rotates The star positions in the Hipparcos projectile into Comet Tempel-1 in 2005, it 15% faster and thus is twice as massive catalog, dating from 1991, are accurate to couldn’t see the fresh crater through the as previously about a thousandth of an arcsecond (one impact’s cloud of debris. The Stardust- thought. That milliarcsecond). Stars, however, move on NExT project is a cheap opportunity to go puts us on equal the sky: each has its own “proper motion.” back to Tempel-1 and look. SDSS / NASA / CXC / SAO / A. VIKHLININ ET. AL. Andromeda Gal- But the Hipparcos catalog will be 20 years (5,700 miles) above Earth, whose moving To help get there, on January 14th footing with the Hipparcos measured this also, to an Stardust fl ew only 9,200 kilometers accuracy of about 1 milliarcsecond per year. axy (M31) mass- gravitational fi eld boosted it into a new old by the time J-MAPS fl ies in 2012, so the wise, even though orbit that will take it to Tempel-1 in uncertainties in our knowledge of stars’ the Milky Way has February 2011. positions, adding up year by year, will be fewer stars. On the Milky The new 1-milliarcsecond catalog of Way map here, approaching 20 milliarcseconds by then. Contributing editor Jonathan McDowell positions from J-MAPS will reset the clock. covers more missions at Jonathan’s Space the red dot marks the location of the Sun. Even better, the two-decade baseline will Report: www.planet4589.org. Yellow dots show the locations of radio give more accurate proper motions as well, masers measured in the study. so we’ll be able to predict precise stellar positions for the rest of the century — and Surprising Trove be able to better map the Milky Way’s of Gamma-Ray Pulsars rotation, the motions of star streams, and members of widely dispersed NASA’s Fermi Gamma-ray Space Telescope moving groups (disintegrated clusters (formerly known as GLAST) has gotten and associations whose stars were born off to a fl ying start. In January its handlers around the same time and place). NASA announced a major new fi nd: the sky is J-MAPS will complement Europe’s On January 14th the aging Stardust craft alive with gamma-ray-only pulsars. Fermi much more ambitious Gaia mission, swung by Earth on the way to its next spotted 13 of them in its fi rst four months. expected to launch in December 2011. Gaia cometary mission. SkyandTelescope.com April 2009 17 © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

News Notes Pulsars (spinning neutron stars) sweep outer mantle, with most of its mass, was planets orbit within narrow beams of radio emission around ejected spherically, creating a round blast 5° of each other, the sky, but for some pulsars this is barely wave. But the star’s inner core blasted out according to an inge- the tip of the iceberg. “The real power in a fl attened plane, especially as high- GREG BACON / STSCI / NASA nious new analysis of these objects is in the gamma rays,” velocity jets that may have been directed of the two planets’ says Fermi science team member Roger along its rotation axis. observed gravita- Romani (Stanford University). Apparently “Now we have to turn this data over tional interaction. the rotating gamma-ray beams are much to the theorists who simulate supernova Whether this rule holds true generally is wider than the radio beams, are oriented explosions and say, ‘Make this!’” says still unsettled. diff erently, and Tracey DeLaney (MIT Kavli Institute). originate in “We don’t understand how we get both the Not So Many Brown Dwarfs diff erent areas round and fl at parts.” The smaller and cooler stars become, the NASA / FERMI / CRUZ DEWILDE pulsars. Fast-Forming Planets more of them you fi nd — at least until around the In the illus- you get deep into the range of the cool- est red dwarfs. Then, it turns out, the If the gas-and-dust disk around a young tration here, a spinning of objects in the Sun’s neighborhood is pulsar emits star wants to create Jupiter-size planets, trend reverses. The best ongoing survey it has to do so fast, according to new beams of radio energy along its magnetic research. In the fi nding that brown dwarfs, objects with axis (shown green) and much stronger sparse, 5-mil- even less mass than red dwarfs, are much gamma-ray fl ashes in diff erent directions lion-year-old star less abundant than was expected from the (purple) due to charged particles radiating cluster NGC trend. Astronomers with the RECONS elsewhere in the object’s intense magnetic 2362 in Canis project (Research Consortium on Nearby fi eld. The pulsar’s spin axis in the illustra- Major (infrared Stars) announced in January that the tally tion its exactly vertical. image at right), of objects within 10 parsecs all solar-mass NASA / JPL / CFA / THAYNE CURRIE (32.6 light-years) of the Two-Part Supernova stars have Sun now includes 239 already lost their red dwarfs but only 12 Astronomers have created a 3-D image protoplanetary brown dwarfs. of the expanding supernova remnant disks. This Some very cool, Cassiopeia A, by tracking the motions of suggests that gas-giant planets, if they infrared-dim ones August 14, 1998 all its pieces as they expand away from its are to form at all, must do so rapidly and have probably escaped center year by year. The remnant, seen in effi ciently before the disks disperse. The notice, but there’s not X-rays below, is only 330 years old. The 3-D fi nding matches recent evidence that giant enough room left for perspective makes clear that the stellar planets in our solar system formed in just very many to hide. MICAELA STUMPF / NASA / ESA (2) explosion had two components. The star’s a few million years, much faster than the Moreover, brown 5.6 AU terrestrial planets. dwarfs are showing a particular aversion to July 31, 2005 Exoplanets in the Same Plane forming binary pairs with normal stars, though they often pair Nearly three dozen stars are now cataloged up with each other — as in the infrared with two or more exoplanets tugging on Hubble images above of the binary Kelu-1, them and giving them slight radial-velocity which has a 40-year orbital period and wobbles. Do the planets of these stars orbit widened greatly from 1998 to 2005. Its two in nearly the same plane, like the planets in members weigh about 61 and 50 Jupi- NASA / CXC / SAO / DANIEL PATNAUDE, ET AL. Or do they orbit in diff erent planes oriented unresolved binary. ✦ our solar system, as you’d expect in a sys- ters, judging by the orbit. Moreover, the tem spawned from a protoplanetary disk? brighter one itself shows signs of being an every which way, as you might expect if the system went through a time of chaotic All News Note stories are presented l N Al interactions? in greater depth, with links to further in gr In the case of Gliese 876, a red-dwarf infor information, at SkyandTelescope.com; sear 18 April 2009 sky & telescope star in Aquarius, at least two of its three search for the keyword SkyTelApr09. © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Cosmic Relief David Grinspoon Mars: Feel the Vibe The long history of false alarms about life on Mars illustrates our eagerness to fi nd such signs. I am writing this on a transatlantic fl ight and was These methane observations test our notion that we just handed a Dutch candy bar with the label “Mars: Feel might detect life on distant exoplanets by fi nding anoma- the Vibe” — appropriate for a day when my morning inbox lous gases in their atmospheres. Earth’s atmospheric was inundated with messages asking if life has really been chemistry is thrown out of whack by life. Oxygen is not found on Mars. That’s what I get for taking a day off ! Every just a trace gas but one-fi fth of our air. With every breath, time life is discovered on Mars, I seem to miss it. When we take in oxygen that has been produced by plants and Martians were announced in a 1996 press conference, I use it to burn food and obtain energy, returning carbon was relaxing in the mountains and was astounded to see dioxide to the air, where plants can use it to make more newspaper headlines declaring “Life on Mars.” Behind the food. Earth’s atmosphere is integral to our biosphere — a hype, there was a signifi cant discovery — tiny, segmented conduit transferring chemicals between oxygen produc- structures in a meteorite from Mars that might be micro- ers and oxygen breathers. It’s much more than a passive fossils, though skeptics declared they were simply quirky dump for occasional waste gases. Mars, with its ancient, mineral formations. This debate is still unresolved. immobile surface and its nearly pure CO atmosphere, 2 And now the media is again declaring “NASA does not seem like a planet with a global biosphere. But Announces Life Found on Mars!” And once again, if you could it have isolated pockets of underground life? cut through the hype, you’ll fi nd an important discovery: Even seemingly isolated niches of underground life methane. It was found with much more rigorous methods on Earth are evolutionary off shoots of a biosphere that than previous disputed detections. Methane is a big deal has co-evolved with our planet over billions of years. If a because it shouldn’t be there. Sunlight and atmospheric global biosphere is like a living organism, requiring the chemistry make short work of it, so there must be an complex interplay of many systems, then fi nding isolated active supply, something geological or even biological. life on an otherwise dead planet might be as unlikely as What’s really new are maps showing seasonal variations fi nding a beating heart without a warm body. and localized sources. Methane is concentrated If life exists on Mars today, it’s a very diff erent beast in the summer in locations that may be from Earth life, and has a completely diff erent associated with unusual geology. relationship with the rest of its planet. We A few discrete methane sources seem to really want Mars to be another don’t argue for a globally perva- Earth, but it isn’t — and hasn’t been sive biosphere, even a buried for at least 3.5 billion years. Perhaps one. But they may be more it will be again in the future. In the consistent with the “sur- case of Mars, wishing may make viving oases” model of life it so. It’s only a matter of time — pockets of organisms before there really are Martians. hanging on in a few areas, We’ll keep announcing them remnants of an ancient until we actually fi nd them, or, glorious biosphere. failing that, eventually become them ourselves. ✦ MARS METHANE MAP David Grinspoon is Curator of Red areas have the highest levels of methane release (30 Astrobiology at the Denver Museum of parts per billion) during the Nature & Science. His website is www. TRENT SCHINDLER / NASA Northern Hemisphere summer. funkyscience.net. 20 April 2009 sky & telescope © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Cosmic Mystery Solved? Shedding New Light on Dark Matter g g g g g g govert schillingooooooooooovvvvvvveeeerrrrrrrrrrrttttttttttttttttt ssssssssssssssssssssccccccccccccccccccccchhhhhhhhhhhhhiiiilllllllllllllllliiiiiiiiinnnnnnnnnnnnnnnngggggggggg Two instruments may have seen telltale signs from the strange stuff that makes up the bulk of the universe’s mass. EUROPEAN SOUTHERN OBSERVATORY Starting in November 2008, a fl urry of Astronomers have gathered overwhelming evidence for papers began crisscrossing the Internet off ering various dark matter’s existence. Its extra gravity provides the most interpretations of some of the most exciting astronomical straightforward explanation for the observed rotation pat- data to come along in recent years. Two groups, one using terns of galaxies, the motions of galaxies in clusters, and a satellite and another a balloon, reported a surprising the bending of distant starlight by intervening clusters. excess of certain high-energy particles coming from deep Moreover, the only cosmological models that are compat- space. These observations might be explained by dark ible with the observed cosmic microwave background and matter: the mysterious “stuff ” not made of atoms that the current distribution of galaxies are those with dark constitutes the bulk of the universe’s gravitating mass, matter outweighing familiar matter by nearly 6 to 1. but whose nature remains shrouded in mystery. However, Astronomers have good reason to suspect that dark they could instead point to one or more nearby pulsars matter is out there, and in humongous quantities. But — a type of object known to exist. what, exactly, is it? Most physicists think it consists of an 22 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

PAMELA SMALL SATELLITE, BIG SCIENCE Like ATIC, PAMELA registered a higher-than-expected Since its June 15, 2006 launch, the number of high-energy particles. PAMELA sees a sig- European PAMELA satellite has nifi cantly lower energy range than ATIC, so it couldn’t detected more positrons (the confi rm the important sudden drop in the number of antimatter partner of electrons) particles above 800 billion eV that was seen by ATIC. But than theorists expect from the two datasets appear to match pretty well in general. nearby known astronomical Apparently, something in our cosmic neighborhood spews objects. PAMELA is operated by scientists in out large numbers of energetic electrons and positrons. Italy, Russia, Germany, Could it be a nearby cloud of annihilating dark mat- and Sweden. ter? That’s one possibility. Noting that positrons are the smoking gun for dark-matter annihilations, University as-yet-undiscovered type of particle that barely interacts of Michigan physicist Gordon Kane, who is not a mem- with normal matter. Frustratingly, eff orts to identify ber of either group, comments, “It’s fairly likely that the dark-matter particles, both in physics experiments on PAMELA group has observed dark matter. This could Earth and in the universe at large, have come up empty indeed be extraordinarily exciting, and the case for that or inconclusive, even though the elusive stuff should detection can be strengthened in the coming months.” leave some tangible trails (S&T: August 2008, page 30). According to popular theories in high-energy physics, A Accordingccordin r p dark-matter dark-matter particles act as their own antiparticles, and when they interact (which should happen in the dens- when they i in est dark-matter clumps), they annihilate, producing a est dark-ma att shower of particles that include electrons and positrons shower of p pa (the antiparticle of electrons). The debris should include rti (the antipar other particles that quickly decay, generating a telltale other partic cle y s gamma-ray signal. gamma-ray Past observations have hinted that some galactic Past obs er gamma rays might originate from this process, but these gamma ray ys whispers are by no means convincing (S&T: December whispers ar 2006, page 42). Instead, the new results involve the discov- ery of what could be the actual decay products of anni- hilating dark matter: cosmic rays consisting of speedy electrons and positrons. BALLOON-BORNE LAB Packing a Punch The international ATIC balloon One fi nd was reported in the November 20, 2008 Nature experiment has fl own several times over Antarctica. During by an international team led by John P. Wefel (Louisiana two fl ights earlier this decade, State University). This group operates a balloon-borne it picked up an excess of high- instrument known as ATIC (Advanced Thin Ionization energy electrons from deep Calorimeter). During two fl ights over Antarctica in 2000 – space that might have come 01 and 2002–03, ATIC registered 210 high-speed electrons from annihilating dark matter. coming from deep space — 50% more than the expected ATIC is a collaboration of sci- 140. The electrons had energies roughly between 300 and entists from the U.S., Russia, 700 billion electron volts (eV), meaning these subatomic China, and Germany. particles have almost as much kinetic energy as a fl ying mosquito. Since such energetic particles lose their punch while traveling through interstellar space, the fi nd indi- cates a relatively nearby source of high-energy electrons. Meanwhile, a team led by Piergiorgio Picozza (Uni- versity of Rome Tor Vergata, Italy) reports an excess of high-energy positrons up to about 100 billion eV. The T. GREGORY GUZIK / LOUISIANA STATE UNIVERSITY claim, submitted for publication in Nature, is based on observations from the European PAMELA satellite (Pay- load for Matter-Antimatter Exploration and Light-nuclei Astrophysics), launched in June 2006. SkyandTelescope.com April 2009 23 © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Cosmic Mystery Solved? Low-energy photons Protons Antiprotons Gamma rays Positrons Electrons Supersymmetric Particles of neutralinos familiar matter (dark-matter particles) Neutrinos ANNIHILATING DARK MATTER According to supersymmetry theory, a type of weakly interacting massive particle (WIMP) known as the neutralino should be left over from the Big Bang. When two of these particles come very near each other, they S&T: CASEY REED annihilate and produce a shower of familiar particles, which quickly decay into other particles and photons. ATIC and PAMELA may have seen electrons and positrons from these decay events. But there are a few catches. First, dark matter might particles would exist in a tiny, rolled-up fi fth dimension, have to be even more mysterious than physicists imag- from where they could make their presence felt in our ined. According to conventional wisdom, the most viable four-dimensional space-time. The existence of higher- candidate for the dark-matter particle is the neutralino, a dimension particles is a prediction of string theory, which heavy particle predicted by supersymmetry — an uncon- is another mathematical construct not yet supported by fi rmed but popular theory that would help resolve linger- observations. Moreover, the Kaluza-Klein explanation ing problems with the Standard Model of particle physics. works best if the dark matter is very strongly clumped, But some physicists argue that a smooth distribution of otherwise the annihilation signal would be much weaker annihilating neutralinos can’t produce the observed spike than the observed electron and positron excess. in the number of high-energy particles seen by ATIC. But according to Dan Hooper (Fermi National Accel- Instead, writes Wefel’s team, if ATIC’s observations are erator Laboratory) and two colleagues, a nearby clump of due to dark matter, the electron spectrum’s drop off above neutralinos could also do the trick. “Computer simula- 800 billion eV suggests they come from annihilating tions tell us that dark matter is not distributed smoothly Kaluza-Klein particles (named after the early-20th-cen- throughout the Milky Way, but is likely to be clustered tury theorists Theodor Kaluza and Oskar Klein). These together in many dense clumps,” he says. “If one of the larger or denser clumps happens to be within a few ANOTHER POSSIBLE thousand light-years, than CULPRIT Annihilat- neutralinos could easily ing clumps of dark produce the signals seen by matter are not the only PAMELA and ATIC.” possible source of high- speed electrons and The Skeptics Chime In positrons. One or more ILLUSTRATION BY CASEY REED / PENN STATE UNIVERSITY pulsar doesn’t happen as Wim de Boer (University Other physicists, however, nearby pulsars could be express the same skepticism spitting them out. If a of Karlsruhe, Germany): “I’m to beam its cones of pretty sure the latest mea- radiation in Earth’s surements are not due to dark direction, it could be matter.” extremely diffi cult to Part of this skepticism detect. there are plenty of other 24 April 2009 sky & telescope stems from that fact that © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

FERMI ON THE PROWL known as GLAST) discovered more than NASA’s Fermi Gamma-ray Space Telescope is a dozen gamma-ray-emitting pulsars that detecting gamma rays across a wide range of ener- haven’t been observed at any other wave- gies. Fermi will probably confi rm or refute the notion length (see page 17). So maybe it’s too early that signals seen by ATIC and PAMELA are coming from to discard the more mundane explanations dark-matter annihilations. for the ATIC and PAMELA observations — even though the PAMELA team notes that S&T: CASEY REED objects that can accelerate electrons and positrons to the “none of the published models fi t our data well.” observed energies — including pulsars, supernova rem- Meanwhile, have dark-matter particles been captured nants, and microquasars (an active type of X-ray binary on Earth? There are unconfi rmed and disputed direct- fuelled by accreting black holes). Martin Pohl (Iowa State detection claims from the DAMA collaboration in the University) has calculated that the narrow peak in ATIC’s underground Gran Sasso National Laboratories in Italy. electrons around 500 billion eV can be explained by a But other ground-based experiments have found no single nearby pulsar, if it’s younger than about 100,000 evidence of dark-matter particles. Just recently, even the years. The pulsar could be anywhere in the sky: electrons extremely sensitive underground ZEPLIN-III dark-matter and positrons are easily defl ected by interstellar magnetic search experiment in England reported a null result. fi elds, so their arrival directions don’t hold any useful information about the source location. And as Picozza A Solution Soon to Come? notes, “Well-known pulsars could give this signal.” Fortunately, Fermi observations could help clarify the The problem is that any pulsar (or other cosmic par- issue in the next few months. Fermi’s sensitive gamma-ray ticle accelerator) would have to be within 3,000 light-years instrument might actually see the or so, otherwise the particles would have lost most of telltale glow of decaying particles their energy before reaching Earth. “Even if what we’ve that are produced by dark-matter SPEED = ENERGY seen with ATIC is not due to dark matter, but is rather annihilation — a faint glow that is For tiny particles such as electrons from a pulsar or some other object, the result is still very predicted to be most conspicuous and positrons, it makes no sense to refer to their masses. Instead, exciting,” says ATIC team member Greg Guzik (Louisi- in a large area centered on the core physicists generally refer to them ana State University). “This would be the fi rst time that of our Milky Way Galaxy. in units of energy (electron volts, such an object is seen in very-high-energy particles, and Ongoing analysis of PAMELA or eV), with the value depending on that would open a new window for studying our dynamic data will also be crucial. Unlike how fast they are moving. To have and violent universe.” ATIC, PAMELA can distinguish the 600 billion eV of energy observed by ATIC, an electron is moving at Then again, astronomers shouldn’t be too surprised electrons from positrons, and the 99.99999999996% the speed of light. about being surprised by the high-energy universe. ratio of these two particles will Nobody knew about pulsars 45 years ago. Microquasars help physicists determine which were not identifi ed until the 1980s. And just recently, are coming from annihilating dark matter and which NASA’s Fermi Gamma-ray Space Telescope (formerly are coming from known types of astrophysical objects. PAMELA may also be able to report results at somewhat higher energy. And once the European To listen to podcast interviews about Large Hadron Collider (LHC) dark matter with leading scientists, visit turns back on later this year SkyandTelescope.com/skytel. (after last year’s startup ac cident), it could provide the essential information to sort all of this out. “Some of the models require defi nite LHC signals, others require no LHC signal,” says Kane. “If the signal is due to neutralinos, LHC will see some of the associated particles, and in some cases the properties of the dark-matter particles can be studied at LHC.” If these various experiments succeed, the mysterious CERN GENEVA stuff that makes up most of the matter in the universe will become a bit less ethereal. ✦ DARK-MATTER MACHINE? By smashing together protons at near-light speeds, Europe’s Large Hadron Collider may cre- S&T contributing editor Govert Schilling writes on a wide ate dark-matter particles in the lab, enabling physicists to study variety of astronomical topics. He is author of the new book their properties in detail. The Hunt for Planet X: New Worlds and the Fate of Pluto. SkyandTelescope.com April 2009 25 © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Ultimate Monster Mash C SMIC CATACLYSMS 26 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

When giant black holes collide, the surrounding space-time trembles. Robert Zimmerman The collision of two supermassive black holes in the aftermath of a galaxy merger is the ultimate cosmic cataclysm, throwing out more energy for about an hour than all the visible stars in the entire universe combined. Moreover, in order to form the billions of majestic galaxies scattered across the sky, astronomers think that such events must have happened frequently as the fi rst galaxies consolidated and grew. Yet, though the heavens are strewn with innumerable coalescing galax- ies, few supermassive black hole binary systems — the natural precursors to these titanic mergers — have been detected. As noted by a team of astrono- mers in one paper, “It has been somewhat embarrassing that very few cases of binary black hole systems have been confi rmed.” Fear not. At this very moment scientists and engineers are attacking the problem on multiple fronts. Not only are astronomers developing techniques for discovering supermassive black hole binaries, they even hope to someday watch them in real time, as the black holes themselves crash and merge. Big Binaries Astronomers defi ne supermassive black holes as having a mass of at least a half million Suns. Observers have found these monsters in the center of every large galaxy that has been searched. The black holes formed as the galaxy built up by repeated mergers over billions of years. The merger process should also have produced many galaxies with two such behemoths at their centers, with the black holes naturally sinking toward each other to form a binary. But after much searching, astronomers have only managed to cull together a very short list of black hole binary candidates. What makes these binaries so hard to identify has everything to do with their basic nature. They are located in distant galaxies, making them faint and diffi cult to see. More important, black holes, by defi nition, are invis- ible and can only be traced by the eff ects their gravity produces on their surroundings. “It’s hard enough to fi nd a single supermassive black hole,” notes David Merritt (Rochester Institute of Technology). “The chance that you would fi nd two in the same galaxy is even smaller.” The most convincing binary black hole candidates show two energetic components in the galaxy’s central regions, as if the galaxy had a double nucleus. Of these, only NGC 6240 and 0402+379 clearly exhibit evidence of two supermassive black holes. In order to see both monster black holes in the CHRIS HENZE / NASA AMES RESEARCH CENTER holes are still thousands of light-years apart,” explains Christopher Reynolds other systems, the black holes have to be separated enough that they aren’t really part of a binary system at all. “In NGC 6240, for example, the two black (University of Maryland). “They don’t feel each other’s gravity yet.” DEATH SPIRAL This frame from a NASA computer animation shows two black holes spiraling inward en route to a merger. The red, orange, and yellow ribbons represent gravitational waves emanating from the system. SkyandTelescope.com April 2009 27 © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Ultimate Monster Mash SAUL TEUKOLSKY / CORNELL UNIVERSITY, ET AL THE MAIN EVENT In these computer simulation frames from the Caltech/Cornell Numerical Relativity Collaboration, two black holes plunge inward and merge, emitting gravitational waves throughout the process. The dark objects at the top of each panel show the shapes of the black holes; the black curve illustrates the inspiraling orbit of one of the holes. The colored area below depicts the extreme curvature of space-time produced by these massive objects. The depth of the indentation represents the curvature of space, colors represent the rate at which time fl ows, and arrows represent the velocity of the fl ow of space itself. With 0402+379, the two active nuclei are only about 24 motion, it propagates outward from the system as ripples light-years apart, with an orbital period roughly estimated of gravitational waves. The waves rob the system of orbital as 150,000 years (S&T: August 2006, page 17). energy, causing the black holes to draw nearer, with the As this issue went to press, Todd Boroson and Tod Lauer orbital period shrinking each orbit. It is this process that (National Optical Astronomy Observatory) reported a possi- causes such black holes to merge. ble binary in a distant quasar. The black holes are separated Assuming this was happening at OJ287, a team led by by less than half a light-year, and have an orbital period of Mauri Valtonen (University of Turku, Finland), predicted about 100 years. This fi nding awaits confi rmation. that the second outburst would occur on September 13, Other possible binary candidates include “X-shaped” 2007, about 20 days earlier than predicted by Newton’s radio galaxies, of which only about a 100 are known. These equations. To their delight, the outburst began within one sources exhibit two separate radio-emitting lobes at two diff erent angles from their nucleus, forming an X. These lobes are created by jets originating very close to the central black hole. One theory suggests that this X-shaped WARPING SPACE-TIME structure results from a rapid fl ip in the direction of the jet. A Rochester Institute of Technology team is one of Since jets are launched along a supermassive black hole’s several groups that have successfully managed to get spin axis, a black hole merger is one of the few ways to pro- black holes to collide inside a computer. The resulting duce such a rapid fl ip. But this theory remains unproven. calculations give scientists keen insight into what to Then there is OJ287, possibly the most exciting super- expect if experiments are devised to detect low-frequency massive black hole binary candidate of all. Every 12 years gravitational waves. or so this active galaxy suddenly comes to life, emitting energy across many wavelengths in two outbursts about one to three years apart. Astronomers have tracked these outbursts for the past century with increasing accuracy. Scientists theorize that the galaxy has two supermas- sive black holes, weighing approximately 18 billion and 20 million solar masses, with the smaller black hole orbiting the larger in an elongated orbit. The double outbursts are thought to be caused when the smaller black hole makes its close approach every 12 years, diving through the cen- tral black hole’s accretion disk on its way in and out. In November 2005 the fi rst of the double outbursts took place, occurring almost 10 months earlier than pre- dicted by Newtonian physics. But according to Einstein, when two such huge masses orbit each other, they bend space itself, and as the bending changes from the orbital HANS-PETER BISCHOF / MANUELA CAMPANELLI / ROCHESTER INSTITUTE OF TECHNOLOGY 28 April 2009 sky & telescope © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

day of their prediction, on September 12, suggesting that radiation that might impart an acceleration. OJ287 might be the fi rst confi rmed supermassive black These cubes, called proof masses, will be allowed to hole binary (S&T: April 2008, page 16). fl oat freely, with sensors carefully tracking each cube’s Yet there are doubts. In order for this theory to work, location in order to keep the spacecraft centered around the heavier black hole must be around 18 billion solar it. Lasers will also track the position of the three proof masses, by far the most massive black hole yet observed. masses. When a gravitational wave sweeps through the “Whenever you have an indirect determination of some- solar system, the positions of the three masses will shift thing like that and if it gives you a number that is this relative to one another by less than the width of a ura- extreme, you worry,” says Reynolds. nium nucleus. Like buoys on the ocean, one will bob Worse, the evidence for all of these binary candidates upward before the next as the gravitational wave passes by. merely includes measurements of the eff ects of the black By measuring these incredibly tiny motions, LISA will holes on nearby material. In no case have scientists detect the strength, direction, and frequency of the gravi- measured the black hole masses directly. To actually look tational waves. Moreover, because of LISA’s location and at black holes and the eff ect they have on space itself will the large distance between its three spacecraft, the mission require gravitational-wave detectors. will be specifi cally tuned to detect low-frequency gravita- tional waves. Big Detectors Since the larger-mass binaries tend to produce the low- The initial development of such a detector, the Laser est frequencies, supermassive black hole binaries will pro- Interferometer Space Antenna (LISA), has begun, though duce bass notes, making LISA ideally suited to study the its funding prospects remain uncertain, and its launch inspirals and collisions of these titanic objects. “We would is more than a decade away. A joint project of the Euro- expect to see mostly massive black hole mergers early in pean Space Agency and NASA, LISA will consist of three the era of galaxy formation,” explains Robin “Tuck” Steb- spacecraft fl ying approximately 3 million miles apart in a bins (NASA/Goddard Space Flight Center). “We’ll catch triangular formation, orbiting the Sun and trailing about perhaps as many as 200 per year.” 20º behind Earth. Inside each spacecraft will be a cube The technology to keep a proof mass fl oating inde- slightly smaller than 2 inches square and made of an alloy pendently inside a spacecraft, while also measuring its 70% platinum and 30% gold, sealed inside a vacuum and position, lies at the cutting edge of aerospace engineer- shielded as much as possible from any solar and cosmic ing. ESA — with some contribution from NASA — plans COLLIDING GALAXIES The Hubble Space Telescope captured this image of The Mice, two galaxies in the process of merging. Each galaxy probably has a supermassive black hole at its center, and eventually the two black holes will sink to the center of the merged galaxy and collide. HOLLAND FORD (JHU) / GARTH ILLINGWORTH (UCSC / LICK OBSERVATORY) / ACS SCIENCE TEAM / STSCI / ESA, ET AL. SkyandTelescope.com April 2009 29 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Ultimate Monster Mash to fi rst fl y a prototype mission, dubbed LISA Pathfi nder, ent shapes. Astronomers need to understand what these scheduled for launch in early 2011. waves will look like and how to separate the waves of dif- If LISA Pathfi nder works, and the full mission is then ferent phenomena from one another. built and deployed, astronomers will have an instrument To accomplish this, several research groups have used capable of measuring the gravitational waves emanating computer simulations to predict the gravitational-wave from inspiraling black holes near the beginning of the signals. These simulations employ several hundred high- universe. And by measuring the waves from these events, speed processors linked together and working in parallel. astronomers will be able to track their orbits and actually Still, the simulations that re-create the orbits and merger predict the moment of collision. of two black holes can take days. If you tried to run one of the longer simulations on your own desktop computer, it Computer Power would need to go nonstop for almost two decades. Scientists need a reasonably accurate approximation of These simulations are so complex that even these what LISA will see when it fi nally begins observing gravi- supercomputers routinely crash. For one thing, black tational waves. The waves of these events will be passing holes contain singularities, the central point where the through our solar system from many directions, at many density is infi nity. Unfortunately, computers don’t handle frequencies, with their waveforms exhibiting many diff er- infi nity particularly well. Black Hole Dance of Doom 1 Merging Galaxies 2 Black Holes Sink to Center 3 Black Hole Merger Process Spin Alignment 2a 1. Two galaxies, each with a central supermassive black hole, Dynamical collide and merge. 2a. The black Friction holes gravitationally slingshot Merger and Ringdown stars to the outer part of the Center of galaxy merged galaxy. This dynamical friction robs the black holes of angular momentum, causing them to slowly sink to the center of the galaxy. After millions of years, they gravitationally lock onto each other. 3a. If the black Axes Aligned holes are surrounded by a large they radiate gravitational waves, gas disk, they accrete matter from which drives the inspiral process. the disk. 3b. By feeding from a 3d. The shapes of the black holes Inspiral common source, their spin axes become distorted when they are aligned prior to merger. This approach within a few radii of each prevents the merged black hole other, and the merged black hole from receiving a huge kick that starts off distorted. Like a ringing can fl ing it out of the host galaxy. bell emitting sound waves, the 3c. Eventually, the two black black hole radiates away these holes come close enough that distortions in the fi nal phase. 30 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

C1 NASA / CXC / MPE / STEFANIE KOMOSSA ET AL. C2 10 milliarseconds CRISTINA RODRIGUEZ / GREG TAYLOR / NRAO, ET AL. BINARY BLACK HOLES? Left: NASA’s Chandra X-ray Observatory captured this image of the center of galaxy NGC 6240, which is the product of a recent galaxy merger. The two bright blue areas represent a double nucleus; each one is presumably powered by a supermassive black hole. The black holes are about 3,000 light-years apart, so it will take millions of years for them to spiral inward and collide. Right: This high-resolution radio image shows the center of the active galaxy 0402+379 (named for its sky coor- dinates). The two bright spots, C1 and C2, are presumably powered by supermassive black holes. The monsters are only about 24 light-years apart, meaning they are close enough to feel each other’s gravity. Scientists tried a variety of techniques to get around this problem. One trick was to remove the black holes from the equation. Another was to freeze the black hole binaries in position and allow the coordinate system to move about them. DAVID MERRITT / RONALD EKERS / NRAO / AUI; INSET: STSCI In addition, the equations in these simulations natu- rally produce many solutions, most of which are physi- cally implausible. Unfortunately, teaching computers to distinguish between what is realistic and what is not is problematic. Worse, the unreasonable solutions are usually unstable and tend to increase in number. “Because the SMOKING GUN? The Very Large Array radio telescope net- unstable answers grow so rapidly, they dominate,” explains work took this image of galaxy NGC 326. The X-shaped struc- Joan Centrella (NASA/Goddard Space Flight Center). ture comes from jets whose orientation abruptly changed As a result, past attempts to simulate the orbits of millions of years ago. This drastic realignment of each jet can black hole binaries, beginning in the 1960s and continu- be explained by the gravitational torque of another black hole, ing through the mid-1990s, were unable to simulate even which could “fl ip” the spin axis of its partner’s jet. The inset the beginnings of a binary’s fi rst orbit. image was taken by the Hubble Space Telescope. Though there were incremental gains throughout these years, it wasn’t until 2005 that physicists suddenly Both groups found that the presence of black holes succeeded in overcoming these diffi culties. In April 2005 themselves in the equations was less of a problem than Frans Pretorius (now at Princeton University) created a expected, and that their complicated eff orts to deal with simulation that lasted fi ve full orbits. Unfortunately, his them had actually made things more unstable. The two system of equations was diff erent than everyone else’s, teams accounted for the fact that the only part of the black making it diffi cult for others to adopt it. hole that interacts with the real world is the outer bound- Then, in November 2005, the group led by Joan Cen- ary, also known as the event horizon. They could essen- trella and John Baker at NASA/Goddard, and Manuela tially round off the singularity to a very small number S&T: CASEY REED Campanelli’s team at the University of Texas at Browns- with no consequences. Moreover, both groups found a method for allowing the black holes to move through the ville, independently came up with almost identical solu- coordinate grid. tions that worked and could be used by almost everyone. SkyandTelescope.com April 2009 31 © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Ultimate Monster Mash “With a very small change, suddenly all the codes in the world were working,” says Centrella. “Everybody was in the game. It had a huge impact.” Or as Campan- elli (who has since moved to the Rochester Institute of Technology) jokes, “It spread like a disease.” Suddenly, it became possible for computer groups worldwide to simu- late black hole mergers of all kinds, including black holes of equal and unequal masses, some spinning, some not, and with orbits both circular and eccentric. The results have been illuminating, when translated into a sinusoidal waveform. Physicists divide the merger process into three stages: inspiral, merger, and ring- down. As the black holes spiral inward, the waves steadily increase in frequency. Then, as the merger stage begins, BONNY SCHUMAKER (JPL) the amplitude increases suddenly and drastically. The merger stage, however, is very short. Almost immediately the black holes absorb each other and the LISA DISK Joan Centrella leads a team that uses computers to predict the gravitational-wave signals from merging black holes. ringdown phase takes over. Much like the fading of a Here, she poses with a scale model of one of the three LISA ringing bell, the wave pattern dies off until it’s gone. spacecraft. LISA could test her team’s predictions by detecting The simulations produced some interesting surprises. supermassive black hole mergers back to the very early universe. Though scientists had a good idea of what the waveforms would look like during inspiral and ringdown, they had To view computer simulations of black hole not known what the waveform of the merger stage would mergers, and to listen to a podcast interview look like at the moment the two black holes collided. They with NASA astrophysicist Joan Centrella, visit had suspected that it would produce a complex pattern. SkyandTelescope.com/skytel. To their surprise, the merger waveform is amazingly simple. Also, the waveforms of almost all types of binary mergers are surprisingly similar. Though the spins and supermassive black holes at the center of galaxies, what relative sizes of the black holes aff ect the shape of the keeps the merged black holes where they are? waveforms in the inspiral stage, once merger begins the According to a model developed by Tamara Bogdanovic waveforms all look remarkably alike. “In fact, the results and her University of Maryland colleagues (including don’t depend on the initial conditions,” notes Baker. Reynolds), it all depends on the alignment of the black hole spins, combined with how much gas the host galax- The Big Kick ies contain, prior to merger. When two gas-rich galaxies These simulations have already begun telling astrono- merge, the gas acts to align the spins of the two central mers something about the real world, at least a decade black holes, thus slowing the kick down suffi ciently when before LISA is launched. As two black holes plunge they fi nally merge. In gas-poor mergers, however, there toward merger, the computer simulations suggest that is nothing to align the spins, and the merged black hole — depending on their orbit, masses, and spins — the ends up with a huge kick (S&T: September 2007, page 14) gravitational waves will fl y outward asymmetrically, giv- Astronomers at the Max Planck Institute in Germany ing the merged black hole a have identifi ed one possible candidate, a quasar showing BLACK HOLE TSUNAMIS sideways kick. In some cases, a blueshift in its nucleus of about 1,650 miles per second When two supermassive black holes such as when the two black relative to the rest of the quasar, suggesting that some- plunge rapidly inward and merge over an holes are spinning in opposite thing very large there is fl ying outward at great speed. hour, the total energy released is about directions, this kick could be “Most of us started out in general relativity, an Ivory 10 greater than the Sun radiates in that 25 same interval. This easily makes them as high as 2,500 miles (4,000 Tower kind of business,” says Baker. “Now we’re rolling the brightest events in the universe. The km) per second — easily fast up our sleeves doing astrophysics. It’s very exciting.” ✦ merger energy comes out entirely in the enough to fl ing the merged form of gravitational waves. black hole from its host galaxy. Robert Zimmerman writes frequently about space and astron- Not only should space be omy for a variety of publications. His critically acclaimed littered with invisible gigantic matter-sucking black holes new book The Universe in a Mirror: the Saga of the fl ying about at great velocities, most galaxies shouldn’t Hubble Space Telescope and the Visionaries Who Built have supermassive beasts in their nucleus at all, accord- It was published by Princeton University Press. The book is ing to these simulations. Since astronomers routinely fi nd reviewed on page 40. 32 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

S & T Test Report Sean Walker FLI’s MicroLine ML8300: High Resolution for Small Scopes WHAT WE LIKE: Mid-sized CCD with small pixels Robust thermoelectric cooling Compact, symmetrical design ALL PHOTOGRAPHS BY SEAN WALKER WHAT WE DON’T LIKE: Included camera-control software very basic Shutter is too slow for short-exposure fl ats Tiny pixels make this CCD camera a big chip in a small package. If you’re a serious deep-sky imager, chances fi eld and a big focuser. The list can go on, seriously rack- are you’ve been eyeing those CCD cameras with the latest, ing up the costs of a dream imaging platform. greatest, big-chip sensors. But they’re not for everyone. So, is there a way to get big-chip performance without Many of us aren’t willing to invest the cost of a compact a complete makeover of your imaging system? Enter the car on a new camera. Furthermore, those big chips latest addition from Finger Lakes Instrumentation (FLI), require a telescope with a large, well-corrected imaging the MicroLine ML8300 CCD camera. Featuring Kodak’s KAF-8300M monochrome sensor, this camera can deliver FLI MicroLine ML8300 high-resolution images and a big fi eld of view when Supplied with cables and attached to short-focus telescopes and fast astrographs. Thermoelectrically cooled, 8-megapixel, mono- a nosepiece for 2-inch The MicroLine ML8300 sports a number of carefully chrome CCD camera with 2-inch adapter and cables focusers, the FLI MicroLine US price: $4,495 ML8300 is an outstanding considered design features that are not obvious from its Finger Lakes Instrumentation performer for deep-sky utilitarian appearance. Because it weighs only 2¼ pounds 7298 W. Main St., Lima, NY 14485; imagers looking for a mid- and has a symmetrical design, the camera places only minimal stress to your telescope’s focuser. Its 3.7-inch- 585-624-3760, fl icamera.com priced CCD camera. square footprint even makes the ML8300 a good candi- 34 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

date for prime-focus systems where the camera replaces making basic exposures, but I suggest users invest in the telescope’s secondary mirror. third-party software such as MaxIm DL (cyanogen.com) The KAF-8300 chip has an impressive 8.3-megapixel or CCDSoft (www.bisque.com) for more advanced camera array of tiny 5.4-micron pixels. It produces images that are control and post-processing capabilities. The camera’s loaded with resolution, even though the chip itself is mod- USB2.0 interface downloads full-frame images in just estly sized — measuring just 18.6 by 13.9 millimeters. seconds on my 1.6-gigahertz, dual-processor laptop. This While that’s only about a quarter of the size of today’s speed made focusing easy, since screen updates for sub- biggest astronomical CCD cameras, it’s still almost 75% frame focusing exposures were very fast. more imaging area than the KAF-3200E CCD, found in many popular cameras. Its small pixels also mean Bigger is Better? that users moving up from a KAF-3200 chip will see a Although conventional wisdom for CCD cameras states 25% increase in resolution when using the same optical that smaller pixels mean less sensitivity, that’s only part system. Another benefi t of the KAF-8300’s modest size is of the story. The KAF-8300 utilizes the latest microlens that it works well with 2-inch focusers. technology that focuses more of the incoming light onto The ML8300 comes with an AC power supply that the silicon imaging substrate, bending it away from delivers the necessary 12 volts DC, a 15-foot-long USB the surrounding inter-pixel circuitry. This increases cable, and a 2-inch nosepiece that screws into the cam- the camera’s overall quantum effi ciency. The Micro- era’s proprietary mounting thread. A software suite that Line ML8300 boasts a peak sensitivity of about 54% at a includes FLIGrab, FLIFocus, and FLIFilter is suited to wavelength of 550 nanometers (green light). You can also The sensitivity and excellent antiblooming characteristics of the MicroLine ML8300 are evident in this pho- tograph of the Horsehead Nebula, in IC 434, recorded with a 105-mm f/6.7 Astro-Physics Traveler refractor and individual 80-minute exposures through red, green, and blue fi lters. SkyandTelescope.com April 2009 35 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

S&T Test Report S&T RATINGS Bottom-line summary: The MicroLine ML8300 A mid-sized chip with small features Kodak’s KAF- FLI MicroLine pixels for deep-sky imaging. It 8300 monochrome ML8300 CCD camera should be given serious consider- CCD. Although smaller ation by imagers with short-focus Operation ✭ ✭ ✭ ✭ than a frame of 35-mm telescopes and astrographs who Overall value ✭ ✭ ✭ ✭ want to obtain high-resolution fi lm, the chip packs images without compromising 8.3 million 5.4-micron- their telescope’s focal ratio. square pixels into its ✭ ✭ ✭ ✭ ✭ Sensibly perfect. No meaningful improvements possible. active imaging area. ✭ ✭ ✭ ✭ Any shortcomings will go unnoticed in normal use. Note the camera’s ✭ ✭ ✭ Problems noticeable but do not seriously aff ect performance. ✭ ✭ Problems noticeable during normal use — performance compromised. partially open stain- ✭ Problems so severe that the equipment is virtually unusable. less-steel leaf shutter Ratings are intended to convey performance compared with equivalent equipment and should not be used to predict the relative performance of instruments having discussed in the accom- markedly diff erent designs or specifi cations. panying text. order the camera with a CCD that doesn’t have an integral The ML8300 is an anti-blooming camera, meaning glass cover, upping the quantum effi ciency to about 60%. that bright stars will not have distracting streaks appear- Quite respectable for such small pixels, especially when ing in the images. As a test, I imaged IC 434, which you consider that another popular Kodak chip, the KAI- includes the Horsehead Nebula, with the brilliant star 11000M CCD with 9-micron pixels, is roughly 20% less Zeta Orionis in the fi eld — the bane of non-antiblooming effi cient. Of particular interest to deep-sky imagers is the chips. Even with 20-minute exposures, there was no sign ML8300’s good sensitivity at the hydrogen-alpha (Hα) of blooming, and Zeta remained a circular blaze (see page wavelength of 656.4 nanometers; sensitivity here is 44 to 35). Shots of M45, the Pleiades, were just as impressive. 49% depending on the cover-glass option. Evidence of the ML8300’s sensitivity occurred one evening when I was recording a series of eight 15-minute Under the Stars unfi ltered exposures of M45 with a 4 1/ 8-inch f/4 astro- I followed the camera’s directions for installing the FLI graph. The resulting stack of images revealed almost software and drivers on my PC, running Windows XP3 two-dozen known asteroids in the fi eld, many as faint as and my own copy of MaxIm DL 4.58. At this point, I ran 18th and 19th magnitude. That’s remarkable for such a into a minor glitch. Although the camera functioned small aperture — this camera has wonderful potential for well and I was able to capture images, this older version asteroid work. of MaxIm DL didn’t allow the camera’s cooling meter to One concern I had was with the shutter. The camera function properly, and I couldn’t monitor the power con- I borrowed for this review included the standard 42-mm sumption of the thermoelectric cooler (TEC). Operating stainless-steel leaf shutter rated for more than 100,000 the camera near the TEC’s 100% capacity can cause dif- cycles. This sounds like a lot, but I can see imagers ferences in the thermal characteristics of light and dark churning through these before too long, considering frames, producing noisy images. Upgrading to MaxIm DL focusing operations and the like. Also, on two very cold 5.0 rectifi ed the problem. FLI later informed me that there (0°F) nights, the shutter would sometimes stick. is a small software patch available for people running the Although the shutter adequately blocks light from hit- older version of MaxIm DL. ting the chip, I found that fl at-fi eld exposures needed to The ML8300’s TEC is excellent. On warm evenings be roughly 10 seconds or longer to guarantee that radial when the ambient air temperature was 24°C (75°F), the shading from the shutter blades would not appear in my TEC cooled the chip to –30°C in roughly fi ve minutes. I calibrated images. While I’ve sometimes dispensed with never experienced any frosting of the camera’s window, fl at-fi eld calibrations when working with cameras that even in my perpetually moist New England climate. have small CCDs, the size Throughout the autumn and winter seasons, cooling was of the KAF-8300 chip all but never a problem. The raw, uncalibrated images from the ML8300 were KAF-3200E KAF-8300 Shown here at actual size, the most noise-free images I have ever taken with an the Kodak KAF-8300 CCD astronomical CCD camera. Using just the hot-pixel- KAF-6303E has an active imaging area rejection fi lter included with most image-processing KAI-11000M that packs an impressive 8.3 programs, I could clean up the raw images, making them million 5.4-micron-square virtually indistinguishable from images that were prop- pixels into an area measur- erly calibrated with dark frames! That’s impressive. KAF-16803 ing 18.6 by 13.9 mm. 36 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

This view of the western half of the Veil Nebula, NGC 6960 in The KAF-8300 requires Cygnus, showcases the MicroLine ML8300’s impressive sensitiv- 2-inch fi lters to avoid seri- ity to hydrogen-alpha light. Total exposure was 3 hours through ous vignetting. This fl at- an Astro-Physics Traveler refractor and Astrodon 6-nanometer fi eld exposure recorded Hα fi lter. To view more images taken with this camera, visit with a fi lter wheel having SkyandTelescope.com/skytel. 1¼-inch fi lter shows the vignetting caused by the undersized glass. necessitates the need for fl at-fi eld calibration to get rid of optical vignetting and image artifacts caused by dust that inevitably lands on the window of the CCD chamber and was able to attach my fi lter wheel by using a custom-made the fi lters. FLI off ers a faster shutter as an option, which is extension tube connected to a recessed T-thread just in nice for people who have to make short fl at-fi eld expo- front of the shutter. But I had to be careful not to screw sures. The camera’s shutter is also user replaceable. the adapter in too far, because it could interfere with the While the ML8300 functions perfectly in 2-inch focus- shutter blades. FLI’s adapters are a better choice. ers, it also requires 2-inch fi lters to properly illuminate Overall, the MicroLine ML8300 represents an out- the chip. I tried using 1¼-inch fi lters in a third-party fi lter standing value for those considering stepping up to a wheel, and the small fi lters introduced signifi cant vignett- high-resolution, mid-sized CCD camera. Its sensitivity ing. Furthermore, refl ections from the inner edge of the and effi ciency made imaging faint targets a breeze. It’s a fi lter cells created annoying arc-shaped artifacts along the big camera in a small, convenient package that will be a edges of my images. Consider the FLI-CFW-1-5 2-inch great CCD setup for short-focus telescopes. ✦ fi lter wheel ($895) plus a set of fi lters if you plan on color imaging. Filter wheels and accessories from other vendors S&T imaging editor Sean Walker nearly froze his nose off can also be adapted to work with the MicroLine cameras, this winter while working with the MicroLine ML8300 at his and FLI off ers a host of adapters for just this purpose. I MASIL East observatory in southern New Hampshire. SkyandTelescope.com April 2009 37 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

S & T Test Report Joe Heafner TheSkyX Student Edition An esteemed planetarium program is now available for PCs and Macs. TheSkyX Student Edition US price: $99 Software Bisque www.bisque.com System requirements PC: Windows XP or Vista, 1.5-GHz Pentium processor or better, 512 megabytes of RAM, Open QL 1.5 or later, 1024-by-768 display, 128 megabytes of video RAM, 520 megabytes disk space, CD-ROM drive. ISTOCK.COM / SWEETYM Mac: Macintosh OS X 10.4.8, G4 PowerPC or Intel 2- GHz Intel Core Duo processor or better, 512 megabytes of RAM, 1024-by-768 display, 64 megabytes video RAM, 520 megabytes disk space, CD-ROM drive. The much-awaited TheSkyX Student Edition can display a realistic naked-eye view of the sky, complete with user-confi gurable clouds and a photorealistic foreground. You can easily add buttons to the toolbar for one-click access to specifi c functions. I have not anticipated a software release as much as can still do so if you want to use a precise location or if I have Software Bisque’s TheSkyX Student Edition. While you have no Internet connection. previous versions of this planetarium program are run- After estimating your location, TheSkyX presents a ning on thousands of personal computers, I’ve been left standard sky display with an uncluttered toolbar along out of the party because of my non-compatible computers. the top of the screen. Buttons can be added to the toolbar But TheSkyX can be used on both Mac OS X and Windows. by those who wish to avoid navigating menus to per- Given the astronomical community’s high regard for form specifi c functions. Most of the buttons intuitively previous versions, I couldn’t wait to install TheSkyX on represent their functions. For example, I had no problem my MacBook Pro running OS X 10.5.6 with a 2.16-GHz recognizing the buttons to toggle on and off coordinate Intel Core Duo processor, 2 gigabytes of RAM, and an grids, constellation boundaries, and constellation fi gures. ATI Radeon X1600 graphics card. There are, however, several buttons that aren’t very When you launch the program, it uses your Internet intuitive. My experimentation showed that the Terrestrial connection to establish your approximate geographic loca- Sphere button displays a conventional Earth-based view tion. While the precise mechanism behind this capabil- of the sky with, if desired, a photorealistic landscape and ity eludes me, I know that it involves your computer’s IP confi gurable clouds. Clicking either button for Free Rota- address. It does work, and it means you no longer have to tion or Celestial Sphere causes the landscape to vanish explicitly set your location within TheSkyX. Of course, you and allows you access to the entire sky. I see no functional 38 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

solar-system objects can be WHAT WE LIKE: generated, which is handy for following comets, aster- Computer’s IP address determines your oids, and planets. geographic location Three-dimensional views Automated download of of our solar system and artifi cial satellite data nearby stars can be called Realistic simulation of up and navigated by mouse. Iridium satellite fl ares There is a conjunction fi nder for events involving WHAT WE DON’T LIKE: solar-system objects, and a viewer for solar and lunar No automated down- loading of asteroid data eclipses. A calendar with The author especially liked TheSkyX’s ability to show simulated heauthorespecially liked TheSkyX’s ability to show simulated the times of sunrise/sunset, T Iridium satellite fl ares with a visual aid that helps pinpoint the Minor interface bugs in initial software release moonrise/moonset, and fl are’s location in a daytime sky (as shown here). Iridium fl ares can be gener- ated. And there’s a useful distinction between these two buttons, and the otherwise lunar map that can be used to identify craters. excellent user’s manual doesn’t mention them. While TheSkyX comes from a time-tested lineage, this When you move the cursor over any celestial object, new incarnation has a few minor bugs, mostly in the a small pop-up window appears with the object’s identi- user interface. The developers are aware of these, and an fi cation and other pertinent information. This is handy update to TheSkyX is due in early 2009. Thus, these bugs because it eliminates the extra step of clicking on the may be fi xed by the time you read this. object to display the information. If you do click, you dis- I am glad to see the highly regarded TheSky is now play a red reticle similar to that on a Telrad fi nder, which a cross-platform product. Users of modern operating is an aid for navigating the real sky with a telescope. systems will no doubt hold TheSkyX in as high esteem as Clicking and dragging the cursor highlights a rect- the previous versions of the program. TheSkyX Student angular region on the display, and TheSkyX immediately Edition is the fi rst member of a family of products off ering zooms this view when you click inside the region. I also diff erent feature sets for diff erent users’ needs. Advanced found that using two fi ngers on the trackpad of my laptop versions off ering telescope control and ultimately complete computer zooms the fi eld of view. observatory automation, are due out in the near future. An increasing number of planetarium programs now The big three commercially developed planetarium include the ability to predict the visibility of artifi cial programs — Starry Night, Voyager, and now TheSkyX satellites, and TheSkyX is no exception. TLE (two-line — are all cross-platform, and that makes for great com- element) data for satellites can be imported from a fi le or petition in the marketplace. With computer software, directly from the Internet, and TheSkyX will plot satel- competition is always a good thing. ✦ lite paths across the sky. You can even call up a three- dimensional view of satellites swarming around Earth, College instructor Joe Heafner lives in North Carolina and is a reminder of how much junk (well, okay, not all of it is currently writing an introductory astronomy textbook. junk) circles our planet. Particularly noteworthy is that TheSkyX generates fl are Viewing circumstances predictions for Iridium satellites with its own nice little for solar and lunar twist. With the click of the mouse, you can simulate a eclipses are graphically selected Iridium fl are on the screen, and it’s shown with displayed with easy- an observer’s arm holding a green laser pointer aimed at to-confi gure param- the moving Iridium satellite. I like this feature! eters. Seen here is the path of this year’s July The program includes several tools for planning 22nd solar eclipse, observing sessions. A “What’s Up?” feature generates which off ers the longest tables of interesting naked-eye, binocular, and tele- totality occurring during scopic objects visible at a sunset, midnight, or sunrise. the 21st century. Any object in the table can be instantly centered on the computer screen with the click of the mouse. Paths of SkyandTelescope.com April 2009 39 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Books & Beyond robert a. garfinkle The Herschel Legacy The Georgian Star: How William through determination and I could also picture the father and Caroline Herschel Revolutionized eff ort became a key pioneer training his son, John, to polish Our Understanding of the Cosmos of astronomical research. telescope mirrors and search the Michael D. Lemonick (W. W. Norton & Co., 2008). Much of William’s fame night skies with them. rests on his 1781 discovery of I highly recommend this 199 pages. $23.95. ISBN-13 978-0-393-06574-9 the planet Uranus, which he fascinating book for anyone After reading a few pages, I thought initially called the “Georgian interested in not only the discov- this history of the Herschel family, as Star” in honor of his patron, King George ery of Uranus, but in the other ground- presented by science writer Michael III. But that’s just the start. A lot of what breaking astronomical accomplishments Lemonick, was somewhat pedestrian, as we now know about the components of of the Herschel family team. I would have biographies go. He off ers no footnotes or the universe is laid upon the multifaceted liked more information on the role Alex- references to check the accuracy of his foundations established by William. This ander played in William’s astronomical research, just a bibliography instead. book discusses how close each of his theo- endeavors, but despite that, I thoroughly I soon found my initial perception to ries came to our modern understanding, enjoyed my look into the life and times of be incorrect. The author has woven an despite using the tools available to him. this marvelous and important family of intriguing biography of William, his sister William was impelled to discover the astronomers. Caroline, their brother Alexander, and true workings of the cosmos. Lemonick’s their times. The result is a very interesting words made me feel William’s passion Robert Garfi nkle studies the history of presentation of the accomplishments of and drive to discover the entire universe astronomy and is the author of two the German-born British musician, who and to determine how all of its parts work. astronomy books. pamela l. gay The Road to the Space Telescope The Universe in a Mirror biography. The Universe in a Mirror tells how he discusses people. Spitzer became Robert Zimmerman (Princeton University Press, that rarely heard full story in loving detail. an astronomical superhero as he tried to Robert Zimmerman (author of the sell people on the idea of space when he 2008). 270 pages. $29.95. ISBN-13 978-0-691-13297-6 article on page 26) starts his chronicle wasn’t scaling cliff s on vacation. Spitzer I’ve grown up around the story of the of Hubble before humans even ventured was just one of the many people who I felt Hubble Space Telescope. In many ways, into space. He gracefully weaves together I truly knew after reading this book. my life has been punctuated by its devel- stories of the mystery of Eta Carinae, Mirror is entrancing. It successfully opment and science. I was a small child of how little we understand planetary communicates that astronomy isn’t just when it was funded in 1977. I was in high nebulae, and of how such problems can be a career but something that people do school when it launched in solved with the space telescope. because they’re driven by love, passion, 1990. I was an undergrad In pulling together these pieces, and curiosity. It turned Hubble into the when its optics was corrected he skips through time and jour- Holy Grail of understanding and intro- in 1993. And I worked with neys around the world, bringing duced me to scientists as noble in their some of its data in graduate together John Herschel’s strug- pursuit of its creation as the Knights school in the late 1990s. gles of the 1830s to make sense of King Arthur’s Court might’ve been Nevertheless, as much as of planetary nebulae with Lyman on their personal quests. If you love the Hubble has been part of my Spitzer’s 1940s dreams of putting Hubble, this book is a must-read. life, I only knew it as a col- telescopes in space. lection of facts and fi gures; What makes Zimmerman’s Pamela Gay urges you to celebrate the tele- I never really knew its full account wonderful, however, is scope. Just go to www.astronomy2009.us. 40 April 2009 sky & telescope © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

sean walker A Better Backyard Guide The Backyard Astronomer’s Guide, age. It’s good-looking too — though for everyone. Third Edition chock-full of useful information, none The third part Terence Dickinson and Alan Dyer (Firefl y, 2008). of the full-color layouts appear cramped introduces digital or confusing. astrophotography. 368 pages. $49.95. ISBN-13 978-1-55407-344-3 Immediately from the fi rst chapter Yes, digital — it I fondly remember haunting my the authors’ fl uid writing style draws you starts out by stating that fi lm is dead. This favorite bookstore as a college student in in, casually introducing you to the pursuit new section covers everything you need the early 1990s, ogling the big, full-color of the night sky. As in previous editions, to get started taking pictures, including astronomy texts, when I happened upon the fl ow comfortably builds with each some useful parts of Adobe Photoshop. The Backyard Astronomer’s Guide. It wasn’t page, easing you into progressively chal- Guide closes with a set of beautifully as fl ashy as the other books, but I was lenging subjects without missing a step. rendered charts of the Milky Way by quickly taken by its practical information, The text builds through each successive Glenn LeDrew. Opposing pages display a covering all the subjects I was interested chapter, describing today’s plethora of color version and a labeled, black-on-white in as a fl edgling amateur. binoculars, telescopes, mounts, eyepieces, version plotted to magnitude 9. Now in its third edition, Terence and other accessories. Dickinson and Dyer have brought their Dickinson and Alan Dyer have completely We then move on to delve deeply into excellent guide further into the 21st cen- rewritten large sections to keep in lock- everything of interest in the sky, from the tury. I can’t recommend it highly enough. step with the evolving trends. Like an old planets to deep-sky objects. The detailed friend who has grown wiser over time, yet accessible explanation of celestial S&T imaging editor Sean Walker spends this compendium has become better with mechanics should be required reading most of his clear evenings imaging the sky. Brief y Noted Stuart J. Goldman Planetology: Unlocking the ties of extraterrestrial life’s emergence. sensible individuals to Secrets of the Solar System Looking even farther out, a fi nal chapter provide guidance for Tom Jones and Ellen Stofan (National Geographic summarizes the search for and fi ndings of novice and experienced Books, 2008). 218 pages. $35. ISBN-13 978-1-4262-0121-9 planets around other stars. telescope users alike. Generously illustrated (as you’d expect His latest book The forces of nature are limited in num- from National Geographic) and off ering tackles one of his ber. But the eff ects of volcanism, ice, and text with a clear and often personal voice favorite subjects: the air — coupled with other physical proper- makes for a mighty inviting book. It’s not compact yet powerful ties — can shape worlds with widely var- a planetary science textbook, but you’ll catadioptric telescope (a “CAT”), which ied results. By studying other planets and learn plenty. comes in Schmidt-Cassegrain, Maksutov, their satellites, researchers learn things and Ritchey-Chrétien confi gurations. It’s that sometimes have relevance to Earth. Choosing and Using a New CAT: more or less an update of his 2001 book In Planetology, two experienced scien- Getting the Most from Your Schmidt- of nearly the same name, but this edition tists compare and contrast the conditions Cassegrain or Any Catadioptric Telescope in Patrick Moore’s Practical Astronomy throughout the solar Rod Mollise (Springer, 2009). 335 pages. $29.95, Series actually costs less. system by examin- paperbound. ISBN-13 978-0-387-09771-8 Mollise walks you through everything ing the forces that you need to know about these scopes so you have shaped our local If you frequent online discussion areas can make an informed decision to buy one worlds. Among these for astronomical assistance or amuse- and operate it eff ectively. He explores criti- infl uences is life ment, you’ve no doubt seen a message or cal accessories, like eyepieces, as well as itself, so the authors 20 from “Uncle Rod” Mollise. He’s one ancillary products (astronomical software) explore the possibili- of the most helpful, knowledgeable, and and tweaks to enhance observing. ✦ SkyandTelescope.com April 2009 41 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Fred Schaaf Northern Hemisphere’s Sky Patterns in the Sky Here’s a guide to learning the spring constellations one step at a time. Are you a beginner who would like to learn whether their pattern approximates regular geometric the constellations? Astronomy writer Guy Ottewell has shapes or other well-known forms — like the human some advice to make this seemingly formidable task fi gure or the outline of an animal. much easier. Let’s try applying it to the evening sky In the Astronomical Calendar monthly maps, Ottewell scene displayed on our all-sky map. has consciously indicated the conspicuous constellations By the way, in these days of one entirely bad thing by using thicker connecting lines between their compo- (widespread light pollution) and some essentially good nent stars. I agree with virtually every choice he makes. things (Go To telescopes, computer simulations, and Departing winter brilliants. The conspicuous con- astro-imaging), even some highly experienced amateur stellations of winter are now arranged in two stacked lay- astronomers don’t know the constellations very well. ers along the west and southwest horizon. Orion, Taurus, Let’s see if we can rectify that! Auriga, Gemini, Canis Major: all are prominent. Canis Minor is too, though its main pattern has just two stars, The Big one of them fairly dim. That star is easy to fi nd because Dipper’s stars it’s so close to Canis Minor’s 1st-magnitude Procyon. range from At this hour, the only inconspicuous winter constella- magnitude tion far enough above the horizon to observe is Monoc- 1.9 to 3.3, but eros, the Unicorn, which can be found in the gap between their graceful Canis Major, Canis Minor, and Orion. and distinc- Spring’s bright standouts. Of all the spring con- tive pattern stellations now spread across most of the southern and makes this eastern sky, only three might be called conspicuous: Leo, asterism Corvus, and probably Boötes. And to them we can add part easier to of a constellation that’s high in the north: the Big Dipper. recognize than many Leo’s prominence is indisputable. Check out this constellations regal stellar beast high in the south on our map. He has with much AKIRA FUJII 1st-magnitude Regulus and two 2nd-magnitude stars. brighter stars. Perhaps more important are his two geometric patterns: a big hook of stars called “the Sickle” and, somewhat A framework to fi ll. Ottewell off ers his advice in an farther to the east, the right triangle of stars that marks introductory section of his legendary annual Astronomi- his hindquarters. The Sickle is the heart (Regulus), chest, cal Calendar (available at ShopatSky.com). He suggests curving mane, and head of the lion. starting with a framework using just a few bright constel- It’s a good thing Leo has such a prominent front, or lations each month. “Having a framework is the turn- we would have a hard time indeed locating its dim fellow ing-point,” he writes. “Before you have a framework, you zodiac constellation Cancer, the Crab. But Cancer is cen- can hardly do anything with a new fact; after you have a tered between conspicuous Leo and conspicuous Gemini, framework, you can hardly help accumulating facts in it.” between Regulus and Pollux. Which are the conspicuous constellations? Let’s Can you fi nd Corvus and Boötes, plus the isolated but take the April evening sky on our map and try to identify bright stars Spica and Alphard? Can you then start fi lling the obvious constellations. This isn’t quite the same thing in the fainter constellations between them? Try it. We’ll as “bright constellations.” For it’s not just the bright- have more details here next month. ✦ ness of its stars that makes a constellation noticeable. It also matters how compactly those stars are grouped, and Fred Schaaf welcomes your comments at [email protected]. 42 April 2009 sky & telescope © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Sky at a Glance April 2009 2 FIRST-QUARTER MOON (10:34 a.m. EDT). MO ON PHA S E S SU N M ON TUE W ED T H U F RI SA T 6 EVENING AND NIGHT: The waxing gibbous Moon is 5° to 7° to the right of Saturn 1 2 3 4 around dusk, and below it later; see page 48. 5 6 7 8 9 10 11 9 FULL MOON (10:56 a.m. EDT). 12 13 14 15 16 17 18 11 – 26 EARLY EVENING: This is the last good 19 20 21 22 23 24 25 opportunity in 2009 to see the zodiacal light in the evening sky from dark locations 26 27 28 29 30 at mid-northern latitudes. Look in the west 80 to 120 minutes after sunset. 13 DAWN: The waning gibbous Moon is very close to Antares as seen from the mainland PL AN E T VISIB I LIT Y U.S. and Canada. The Moon occults Antares in Hawaii and other Pacifi c islands. ◀ SUNSET MIDNIGHT SUNRISE ▶ Mercury W Visible April 8 through May 5 16 – 24 DUSK: A fi ne apparition of Mercury. It’s magnitude 0 or brighter and at least 10° above the western horizon a half hour after Venus E sunset (for mid-northern latitudes). This is about as favorable as conditions get for Mars Visible starting April 14 E viewing the elusive innermost planet. Jupiter SE 17 LAST-QUARTER MOON (9:36 a.m. EDT). Saturn SE S W 19 DAWN: The crescent Moon hangs 1° to 3° upper right of Jupiter; see page 49. PLANET VISIBILITY SHOWN FOR LATITUDE 40o NORTH IN MID-APRIL. 22 PREDAWN: The Lyrid meteor shower peaks, IMAGE BY DENNIS DI CICCO with the best views likely between 1 and NASA / HUBBLE HERITAGE TEAM / STSCI / AURA 4 a.m. The shower is usually weak but sometimes puts on a surprisingly good performance. DAWN: The waning crescent Moon is spectacularly close to Venus low in the east before sunrise for eastern North America. The Moon occults Venus in bright twilight or morning daylight over most of the continent; see page 56. 24 NEW MOON (11:23 p.m. EDT). 26 DAWN: Through a telescope, the 5th- magnitude star 44 Capricorni can be seen directly between Jupiter and Ganymede, Jupiter’s brightest moon. DUSK: The Pleiades glimmer between Mercury and the waxing crescent Moon in SATURN’S RINGS ARE TILTED almost edge-on to Earth, as they were in Octo- North America. ber 1996 when the Hubble Space Telescope shot the picture above. This makes the rings’ Apr. 28 DUSK: Mercury is less than 2° from the structure diffi cult to discern, but it also makes this a good time to view the subtle band- –May 1 center of the Pleiades. Look with binoculars ings and, perhaps, even subtler spots on Saturn’s globe (see page 53). It’s also an ideal very low in the west-northwest 45–60 opportunity to look for Saturn’s faint innermost moons — which tend to be hidden by the minutes after sunset. rings’ glare at other times in the planet’s 29½-year orbital cycle. SkyandTelescope.com April 2009 43 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Northern Hemisphere Sky Chart h 22 E Facing North M D Z +60n A CASSIOPEIA B 1 h M52 ANDROMEDA 19 h CEPHEUS Vega A G B E D D G Cluster G Facing NE Double E G M34 +80n B N M92 Z DRACO P Algol MINOR G A URSA E H Polaris A B R H CAMELOPARDALIS D PERSEUS Dipper Little G Z B M13 +80n HERCULES Thuban Capella E A B M82 D E B M81 Mo Mizar A BOREALIS & Alcor CORONA H AURIGA B M36 M38 I M A O D Z E A Big Dipper +60n G M51 G B YNX Q B 16 h E I M37 BOÖTES L A Castor Z M3 CANES VENATICI Zenith M35 C 1 SERPENS MAJOR URSA B A E B A M H C 2 N A Pollux B M5 X Facing East LEO Arcturus Moon D G A MINOR A COMA D Z G M44 Apr 2 GEMINI X BERENICES +20n Sickle D E B G H Betelgeuse O LEO Saturn A CANCER M67 CANIS MINOR A E B A Z Procyon Regulus Moon G B E C L I P T I C Apr 6 0n E Q U A T O R M50 B H VIRGO A M48 SEXTANS MONOCEROS A A Sirius Moon Alphard M47 Spica Apr 9 CRA TER M46 D CORVUS A M41 CAN G –20n MA B E M93 D HYDRA A E G H 13 h A PYXIS 7 h Facing SE A PUPPIS ANTLIA B P Z –40n VELA 10 h 44 April 2009 sky & telescope Facing South © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Using the Map Binocular Highlight: M48 in the Desert WHEN Late February Midnight Facing NW Early March 11 p.m. The glittering constellations of winter are a tough 11 p.m.* Late March act to follow. By comparison, the spring sky is a veritable 10 p.m.* Early April A desert. The prime slice shown on our evening sky map lying Late April Dusk between 8 and 10 right ascension is devoid of conspicuous h h *Daylight-saving time groupings and holds no stars brighter than 3rd magnitude. Yet, like earthly deserts, this celestial one isn’t completely barren — it contains several binocular Messier objects, HOW including the open cluster M48, in Hydra, the Water Snake. Go outside within an hour or so Hydra itself is such a sprawling, faint constellation that of a time listed above. Hold the it’s easier to fi nd M48 from Canis Minor. Draw a line from map out in front of you and turn it Beta (β) Canis Minoris to Alpha (α, or Procyon), and extend around so the yellow label for the Pleiades direction you’re facing (such as it 3 times farther southwest to sweep up the cluster. It’s hard Z west or northeast) is at the bottom, to miss M48 — there’s really nothing else there. The nearest landmark is a trio of stars consisting of 1, 2, and C Hydrae. right-side up. The curved edge is oon Under badly light-polluted skies, M48 can be a diffi cult Mar 30 the horizon, and the stars above it fi nd. That’s because the cluster’s brightest stars are only 8th on the map now match the stars in AURUS 4 h center is the zenith, the point though, M48 is quite a lovely sight. My 10×50s show a rich E front of you in the sky. The map’s magnitude, and most are fainter. Under good conditions, A Q Hyades overhead. smattering of faint stars spread over ½°. The cluster has Aldebaran T Facing West Example: Turn the map so the an interesting structure. I see a loose knot of stars at the center, with several curving chains of stars on either side. “Facing East” is at the bottom. It reminds me of a high-school textbook diagram of Earth’s Bellatrix Nearly halfway from there to the magnetic fi eld. map’s center is bright, yellow- Bigger binoculars make all of these details easier to see. L G ERIDANUS orange Arcturus. Go out, face east, Indeed, M48 really comes into its own in tripod-mounted ORION D B and look halfway from horizontal to 15×70s. A couple dozen individual stars pop in and out of view straight up. There’s Arcturus! and give the impression of a pleasingly rich gathering. ✦ Note: The map is plotted for Z E M42 B 40° north latitude (for example, — Gary Seronik Denver, New York, Madrid). If B Rigel K you’re far south of there, stars in CANIS B K the southern part of the sky will be MINOR higher and stars in the north lower. M Far north of 40° the reverse is true. Procyon A LEPUS Saturn is positioned for mid-April. HYDRA A B NIS You can get a sky chart AJOR customized for your location at any time at SkyandTelescope.com/ MONOCEROS Facing SW 2 C 1 M48 skychart. 5° binocular view A SkyandTelescope.com April 2009 45 © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Fred Schaaf Sun, Moon, and Planets Five Planets Grace the Sky For the fi rst time in many months, all the bright planets become easy to see in late April. During the second half of who look 30 minutes after sunset will E V E N I N G A N D N I G H T April, Mercury presents its best evening fi nd Mercury shining at least 10° above Saturn comes into view high in the south- showing of the year for observers at mid- the west-northwest horizon from April east during twilight. It lies in southeast- northern latitudes. All month, Saturn is 16th to May 4th. Although the fl eet little ern Leo near the Lion’s hind foot, well to high in the southeast at dusk and spends world fades during the month, it remains the lower left of Regulus and much farther most of the night crossing the sky. At brighter than magnitude 0 until a few to the upper right of rising Spica, the dawn, Jupiter glares low in the southeast, days before it reaches greatest elongation brightest star in Virgo. Saturn noticeably while brilliant Venus and dim Mars are from the Sun on April 26th. outshines both Spica and Regulus, and just above the eastern horizon. On that date, Mercury is about 19° its light burns more steadily and sedately above the horizon at sunset at mid-north- than that of the twinkling stars. The rings DUSK ern latitudes, but only 8° high an equal are tilted only 3° to 4° from edgewise in Mercury reaches superior conjunction distance south of Earth’s equator. When April, making this a good month to study on the far side of the Sun on March 31st viewed in a telescope, Mercury is then a the globe of the planet and search for but then vaults into dusk visibility during thick crescent 8″ wide and less than 40% Saturn’s faint inner moons (see page 55). mid-April. Skywatchers around 40° north illuminated. Can you detect one or more light or dark bands or a dusky polar region on Saturn? Notice that Saturn’s globe is the most Dusk, April 25–27 Capella April 4–6 oblate of any planet’s, bulging 12% wider 45 minutes after sunset Shortly after dark at the equator than from pole to pole. B Tauri DAW N Pluto is as high as it’s going to get in the Moon Moon south before morning twilight starts, but Apr 27 Sickle Apr 4 at 14th magnitude it’s still a challenging G object even for fairly big telescopes. Jupiter rises more than 3 hours before LEO the Sun by late April, but even at dawn it’s still rather low in the southeast. Jupiter’s Regulus Aldebaran big disk is always pleasing in telescopes, Moon Apr 26 however. This is one of the infrequent Moon Apr 5 years when we’re near enough to Jupiter’s Pleiades equatorial plane to see the planet’s Gali- Saturn lean moons eclipsing and occulting one Mercury another, though we won’t get good views of them until later in the year, when the Moon Moon Apr 6 big planet has climbed out of the murk Apr 25 along the horizon. h Around 17 UT on April 26th, Jupiter’s north pole passes within a few arcseconds Looking West-Northwest Looking Southeast, very high of 44 Capricorni after that star has nearly 48 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

December solstice Mercury ORBITS OF THE PLANETS March September equinox Venus Sun equinox The curved arrows show each planet’s movement Mars during April. The outer planets don’t change position Earth enough in a month to notice at this scale June solstice occulted Callisto (around 19:50 UT on the 25th) and Ganymede (around 4:30 UT on the 26th). North American skygazers can’t Saturn see these events, but we do get a remark- Uranus able view on the morning of the 26th of 44 Jupiter Capricorni directly between Jupiter and Neptune Ganymede. Jupiter glides rather rapidly eastward Pluto among the background stars in April, and it closes the gap on a background planet. Jupiter appears 6½° west of 8th-magnitude Neptune on April 1st and 2½° on the 30th. They will have a close conjunction in May. Venus also changes dramatically in one. Their conjunction in right ascension Venus shines very low in the dawn. It telescopes during April. By mid-month its occurs on April 18th, with blazingly bright begins April rising less than an hour before crescent has thickened from an ultra-thin Venus passing a full 5½° north of Mars the Sun, but by month’s end the interval sliver almost an arcminute long to 11% — which, at magnitude +1.2, is about 200 is closer to 1¾ hours. During these weeks, illuminated and 50″. And by month’s end times fainter. Interestingly, their appulse the always-brilliant planet kindles even those fi gures have changed to 25% and 40″. (actual closest approach on the sky) occurs more, reaching a brightness of –4.7 toward Although Venus remains low at dawn all 6 days later, but even then their separation the end of the month. month at mid-northern latitudes, observ- is more than 4°. ers in the Southern Hemisphere see Venus Back on the morning of April 15th, Mars soar dramatically higher during April. is much closer to a planet almost 100 times To see what the sky looks like at any given time Venus passes Mars in the latter half dimmer than itself. That world is 6th-mag- and date, go to SkyandTelescope.com/skychart. of April, but the encounter is not a close nitude Uranus, which lies less than ½° north (upper left) of Mars that morning — though both are low in the bright dawn Dawn, April 19–23 sky. With a good telescope at medium mag- 40 minutes before sunrise nifi cation, can you glimpse and compare the 4.4″-wide disk of Mars with the much dimmer 3.3″-wide disk of Uranus? Moon MO ON P A SSA G E S Apr 19 The Moon is waning gibbous just a few Moon Apr 20 degrees lower right of Antares at dawn on Jupiter April 13th. On the morning of the 19th a Moon Apr 21 thick lunar crescent is only 1° to 3° upper right of Jupiter as seen from North Amer- Moon ica. A much thinner crescent is even closer Apr 22 10° upper right of Venus at dawn on April 22nd (with Mars less than 5° under them). Venus Moon Apr 23 Mars Back in the evening sky on April 26th, a waxing lunar crescent is about 4° above Mercury. The Moon has then just fi nished occulting the Pleiades, but that event can only be seen well from the middle of the Looking East Looking Southeast Atlantic Ocean. ✦ SkyandTelescope.com April 2009 49 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Charles A. Wood Exploring the Moon Naming Names The rules for lunar nomenclature go back centuries. If you have a detailed lunar map to use with your Tempting fate, subsequent lunar mappers ignored telescope, you’re good to go to navigate our satellite. Take Van Langren’s warning and introduced their own des- a casual stroll across the surface and when you fi nd some- ignations for the same features. Alas, only four of the thing interesting, you can pause and check what it is. features Van Langren named still bear the appellations Alternately, to fi nd a specifi c feature, you can easily jump he gave, and one was the crater he named for himself. from one landmark to the next — like star-hopping. Remarkably, a new set of names bestowed by Giam- This was not always so. The fi rst known lunar chart battista Riccioli in 1651 did take hold and became the with names was published by Dutch astronomer Michael basis of all later lunar nomenclature. Unlike the earlier Van Langren in 1645. At that time intense competition scheme that honored political and religious leaders or among selenographers (Moon mappers) led them to make reused names of terrestrial geographic features, Riccioli maps and to win favor from local kings and nobles by instead commemorated scientists and philosophers. And using their names for features. To ward off rivals, Van since subsequent Moon maps were made by scientists Langren inscribed his map with “changes in the names of they adopted his nomenclature, which we still use today. this map are forbidden under pain of indignation. . . .” Copernicus, Plato, Tycho, and Kepler are some of the 247 familiar names that Riccioli introduced. Riccioli also named the dark maria with terms related THE OPPOSITE OF SEAS Early lunar maps included names for the bright to weather and its eff ects. In the 17th century people areas of the Moon, not just craters and dark “seas.” These designations didn’t thought that the Moon infl uenced Earth’s weather and last, however. Today, such areas are merely referred to as “highlands.” even human personalities. Mare Imbrium is the Sea of Showers, Humorum is moisture, and Tranquillitatis is Terra Siccitatis tranquility. Early selenographers also gave designations Terra Si to the lunar bright areas. Riccioli included the names Terra Caloris, Terra Nivium, and Terra Siccitatis, Terra Pruinae Terra Grandinis meaning Land of Heat, Snows, and Dryness, respectively. Although these bright highland areas of the Moon Terra Vitae often are distinctive, all of their names were abandoned in the 1830s. I still fi nd it geographically useful, even Terra Nivium poetic and reaffi rming, to say Terra Vitae, Land of Life, when referring to the bright terrain north of Mare Cri- sium Terra sium, the Sea of Crises. S Scholars used Latin when lunar nomenclature was Vigoris inve invented. Thus the words for landform types were Latin: mare mare for sea, sinus for bay, and mons for mountain. Dur- ing the 1960s, when human and spacecraft scrutiny ing t Terra fh Terra Manna of the Moon amplifi ed the need for many new names, Sanitatis selenographers extended Latin’s use to other landform Peninsula Peninsula types such as catena, dorsum, and rupes, for crater chain, Fulminu Fulminu ridge, and scarp. These terms lack 400 years of familiar- Terra Caloris Explore the history of senelography at the Linda Hall Library’s GARY SERONIK Terra online exhibit The Face of the Moon: Galileo to Apollo at Fertilitatis www.lindahall.org. Afterward, interactively examine old star atlases and Moon maps in the library’s digital collections. 50 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

LINDA HALL LIBRARY OF SCIENCE, ENGINEERING & TECHNOLOGY THE WAY THINGS WERE Giambattista Riccioli’s 1651 map of the Moon wasn’t the fi rst detailed lunar chart, but his crater-naming convention of honoring scientists and philosophers has endured. ity and many lunar observers fi nd them features that will need designations. The confusing. I don’t use them, preferring resulting new maps and a patriotic desire the understandable English terms. from these new contributors to lunar Lunar nomenclature is fl uid. The exploration will undoubtedly result in the surface has hundreds of unoffi cial names, commemoration of many Asian scientists such as Hell Plain for the crater now and philosophers. Riccioli would welcome called Deslandres, and the Aristarchus it — and so do I. ✦ Plateau for the distinctive area north of the nearby bright crater. In October 2008 When online, contributing editor Charles the International Astronomical Union Wood calls himself “Tychocrater.” offi cially adopted two new names for polar craters — Lenard and Haworth — for N Nobel Prize winners. C 9 A new generation of lunar orbiters from Japan, India, and China will result in ANTONÍN RÜKL much better images of the Moon’s surface, D 5 especially the far side, revealing still more B 18 W E The Moon • April 2009 Apr 4 20 A Highlighted feature Description 22 30 A Terra Caloris Southwestern highland region S 29 B Terra Nivium Highland region near Mare Vaporum C Terra Siccitatis Northwestern highland region For key dates, black dots on the map indicate what part of the Moon’s limb is tipped the most toward D Terra Vitae Northeastern highland region Earth by libration under favorable illumination. Phases Distances Librations h First quarter Apr. 2, 14:34 UT Perigee Apr. 2, 2 UT Mare Smythii Apr. 4 229,916 miles diam. 32′ 18″ Full Moon Apr. 9, 14:56 UT Mare Humboldtianum Apr. 9 Apogee Apr. 16, 9 UT h Last quarter Apr. 17, 13:36 UT 251,178 miles diam. 29′ 34″ Peary (crater) Apr. 16 New Moon Apr. 25, 3:23 UT Perigee Apr. 28, 6 UT Mare Orientale Apr. 22 h 227,446 miles diam. 32′ 39″ Mare Australe Apr. 30 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Ralf Vandebergh Celestial Calendar Challenges on Saturn With Saturn’s rings nearly edge-on, the planet’s globe is wide open for view. The rings of saturn are so spectacular that to be the practical minimum for success. they yank attention away from the planet itself, which is A lot depends, of course, on how big or bright a spot usually rather bland. But this year the rings are turned appears. In 2006 NASA’s Cassini probe orbiting Saturn nearly edge-on to our line of sight (by 2.3° on March 1st, detected radio noise that seemed to come from lightning 3.4° on April 1st, and 4.1° on May 1st). So now is a fi ne in the planet’s atmosphere. The Cassini team had to time to take a closer look at the planet’s softly visible dark search ground-based pictures for signs of a storm spot belts and bright zones — and any detail that might be where the lightning might be happening; Cassini itself detectable within them. Saturn comes to opposition on was behind Saturn’s night side at the time. Most available March 8th and is in fi ne evening view all spring. images were from amateurs, and these indeed showed the Saturn’s bright Equatorial Zone, and the duskiness of big, prominent storm responsible. I imaged it myself with the polar regions, are apparent in a 3-inch scope at fairly my 10-inch Newtonian refl ector. Cassini scientists were high power. The rings’ shadow on the planet currently very grateful for the amateur help in creating a continu- appears (during good seeing) as a thin, vivid black line ous record of the storm’s behavior. It was a great example along the equator. But observing smaller structures and of what backyard planetary observers can still contribute, spots is another matter, assuming they’re present at all. using modern techniques, even when a billion-dollar These features generally require a large telescope, excel- spacecraft is in a planet’s own neighborhood! lent seeing, and persistent, careful examination. Nowadays, however, electronic imaging works better Extreme contrast may result in ugly for such eff orts than even the most skilled eye. Fine plan- pictures, but it can make subtle mark- etary imaging can be done with a cheap video webcam, ings evident. The white spot is the freeware for selecting and stacking the best video frames, giant lightning storm detected by the and image-processing software to enhance the result. To Cassini orbiter in 2006. The image capture Saturn’s storm spots, a 7- or 8-inch scope seems was taken in February of that year. You can record bright white spots like the one in 2006 easily with a webcam and an 8-inch scope. Harder to distinguish are the lower-contrast spots that are present more often. A few years ago I started trying to record these subtler swirls, as well as low-contrast colors in the belts and zones (S&T: May 2007, page 60). One of the most interest- ing results has been cloud activity within the Equatorial Zone. The images look especially good when I make an animation from several of them taken minutes apart. You Subtle but real color diff erences exist among Saturn’s belts and zones. should always do this to verify that any markings are real. They’re invisible to the eye (or nearly so) but can be brought out by care- Genuine features, as opposed to imaging and processing fully exaggerating the color contrast in an electronic image. The author artifacts, will not only persist from image to image but created this stacked-video view a couple years ago when Saturn’s rings will rotate with the planet, which makes them pop right were much more open than they are now. He combined luminance and out to the eye in an animation. RGB color-fi lter images taken with his 10-inch Newtonian refl ector, then I’ve also kept watch on structures that regularly appear processed the result. in Saturn’s darker South Equatorial Belt (SEB), the same belt that’s so active on Jupiter. (Saturn’s North Equatorial Belt was hidden behind the rings until the current appari- SkyandTelescope.com April 2009 53 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Celestial Calendar tion.) The plainest spots appear in the Visit the author’s Saturn site, saturnreport. center of the SEB. Many amateurs record startje.be, for animated images showing these features every year. features rotating with the planet’s globe. 21:48 UT 21:51 UT 21:54 UT Processing a negative image can help bring out details. Here we see many irregular clouds Processing can create or enhance artifacts in Saturn’s bright Equatorial Zone. But be careful — in such a highly processed view, image as well as real features. The way to tell artifacts get exaggerated too. the diff erence is to take a series of images minutes apart and turn them into an ani- mation. Real features will rotate with the More diffi cult, but maybe more inter- have any chance of capturing structures planet, making them plain. Here a white esting, are the darker spots and condensa- like these, it’s important to image as fre- spot in the South Equatorial Belt (just tions that sometimes appear at the edges quently as possible. above center) moves beyond the central of the SEB, and disturbances extending Fortunately, many observers are doing meridian. north-south across its entire width. To so. It doesn’t take much to join them! This year Saturn’s moons are eclipsing and occulting one another. A campaign to observe and time these events is underway. For informa- tion and timetables, see www.imcce.fr/fr/presentation/equipes/GAP/travaux/phemu09. The Mimas Challenge Our monthly fi nder diagram for Saturn’s when Mimas is at its eastern (E) or western satellites (page 56) includes fi ve of them; (W) elongation. The dates and times are in Mimas with the closest to the planet is diffi cult little Universal Time: its giant crater h h h h Enceladus. The diagram omits tiny Mimas March 1, 0.7 E, 12.0 W, 23.3 E; 2, 10.6 W, 21.9 h Herschel, h h h h h even closer in, because it would crowd the E; 3, 9.2 W, 20.5 E; 4, 7.8 W, 19.1 E; 5, 6.4 W 17.7 h imaged by h h h h h lines too much and because most amateur E; 6, 5.0 W, 16.3 E; 7, 3.7 W, 15.0 E; 8, 2.3 W, 13.6 h Voyager 2. h h h h h scopes can’t show Mimas. At Saturn’s mean E; 9, 0.9 W, 12.2 E, 23.5 W; 10, 10.8 E, 22.1 W; 11, h h h h h h opposition it’s magnitude 12.8 compared to 9.4 E, 20.7 W; 12, 8.0 E, 19.3 W; 13, 6.6 E, 17.9 W; h h h h h Enceladus’s 11.8. And worse, it’s deeper in 14, 5.3 E, 16.6 W; 15, 3.9 E, 15.2 W; 16, 2.5 E, 13.8 h h h h h h Saturn’s overwhelming glare. W; 17, 1.1 E, 12.4 W, 23.7 E; 18, 11.0 W, 22.3 E; 19, 22, 7.8 W, 19.1 E; 23, 6.4 W, 17.7 E; 24, 5.0 W, 16.3 h h h h h h h h h h h However, with the rings almost edge-on 9.6 W, 20.9 E; 20, 8.3 W, 19.6 E; 21, 6.9 W, 18.2 h E; 25, 3.7 W, 15.0 E; 26, 2.3 W, 13.6 E; 27, 0.9 W, h h h h h h h h h h this season, their nearby glare is almost gone E; 22, 5.5 W, 16.8 E; 23, 4.1 W, 15.4 E; 24, 2.7 W, 12.2 E, 23.5 W; 28, 10.8 E, 22.1 W; 29, 9.4 E, 20.7 h h h h h h h h h h h and you’ll have your best chance at Mimas. 14.0 E; 25, 1.3 W, 12.6 E, 23.9 W; 26, 11.2 E, 22.5 h W; 30, 8.0 E, 19.3 W. h h h h h h h I’ve never seen it, though I regularly spot W; 27, 9.9 E, 21.2 W; 28, 8.5 E, 19.8 W; 29, 7.1 E, Mimas completes an orbit in just 22.6 h h h h h Enceladus in my 12.5-inch refl ector at 180× 18.4 W; 30, 5.7 E, 17.0 W; 31, 4.3 E, 15.6 W. hours, so you should see its motion during h h h h h and 300×. But my sharp-eyed S&T colleague April 1, 2.9 E, 14.2 W; 2, 1.5 E, 12.8 W; 3, 0.2 E, your observing session. h h h h h h Tony Flanders has seen Mimas in his own 11.5 W, 22.8 E; 4, 10.1 W, 21.4 E; 5, 8.7 W, 20.0 E; If you succeed, what’s the smallest scope h h h h h h 12.5-inch refl ector — once in 1998 and again in 6, 7.3 W, 18.6 E; 7, 5.9 W, 17.2 E; 8, 4.6 W, 15.9 E; with which you can see this little speck? Try h h h h h h 2005 when the rings were wide open! 9, 3.2 W, 14.5 E; 10, 1.8 W, 13.1 E; 11, 0.4 W, 11.7 E, stopping down your aperture, and let me know h h h h h Look within an hour or so of when Mimas 23.0 W; 12, 10.3 E, 21.6 W; 13, 8.9 E, 20.2 W; 14, h h h h h h is at eastern or western elongation from 7.5 E, 18.8 W; 15, 6.2 E, 17.5 W; 16, 4.8 E, 16.1 W; the results. h h h h h the planet. Listed below are the dates (in 17, 3.4 E, 14.7 W; 18, 2.0 E, 13.3 W; 19, 0.6 E, 11.9 h — Alan MacRobert h h h h h boldface) and times (in decimals of an hour) W, 23.2 E; 20, 10.6 W, 21.9 E; 21, 9.2 W, 20.5 E; [email protected] 54 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Titan and Its Shadow Like the rings, the orbits of Saturn’s major satellites are nearly edge-on this year. So the satellites now pass in front of and behind Saturn, casting their tiny shadows onto it just like the moons of Jupiter. Saturn is about twice Jupiter’s dis- tance, however, and only Titan is a match for Jupiter’s big moons. Even so, Titan’s shadow is quite apparent; see image below. Jean Meeus calculated the Titan timetable here. The dates and times are in Universal Time. Oc means an occultation of Titan behind Saturn’s limb. Ec means eclipse in Saturn’s shadow. Tr is a transit of Titan across Saturn’s face. Sh refers to Titan casting its shadow onto the planet. An occultation or eclipse begins when Titan disappears (D) or reappears (R). A transit or shadow passage begins at ingress (I) and ends at egress (E). Each event is gradual, taking several minutes. Phenomena of Titan Date UT E Date UT Eventvent UT E UT Eventvent 6: Mar. 4 11:48 Ec. D.Ec. D.11:48 Apr. 29 6:22 Sh. I.Sh. I.22 11:16 14:48 Sh. E. Oc. R. Mar. 4 14:48 Oc. R. Apr. 29 11:16 Sh. E. Ec. D. Mar. 12 9:34 Sh. I. May 7 7:23 Ec. D. 9:34 Sh. I. 7:23 Tr. I. 12:40 Ec. R. Mar. 12 10:25 Tr. I. May 7 12:40 Ec. R. 10:25 Tr. E. Sh. I. Mar. 12 11:28 Tr. E. May 15 5:26 Sh. I. 11:28 5:26 Sh. E. 10:39 Mar. 12 12:51 Sh. E. May 15 10:39 Sh. E. 12:51 Sh. E. Ec. D. 10:29 Mar. 20 10:29 Ec. D. May 23 6:30 Ec. D. Ec. D. 6:30 Ec. R. Ec. R. 12:06 Mar. 20 13:59 Ec. R. May 23 12:06 Ec. R. 13:59 8:25 Sh. I. 4:32 Sh. I. Mar. 28 8:25 Sh. I. May 31 4:32 Sh. I. 12:23 Sh. E. Mar. 28 12:23 Sh. E. May 31 10:00 Sh. E. Sh. E. 10:00 9:21 Apr. 5 9:21 Ec. D. June 8 5:39 Ec. D. Ec. D. 5:39 Ec. D. Ec. R. Apr. 5 13:37 Ec. R. June 8 11:31 Ec. R. 11:31 13:37 Ec. R. 7:22 Sh. I. Apr. 13 7:22 Sh. I. June 16 3:40 Sh. I. Sh. I. 3:40 Sh. E. 11:51 9:18 Sh. E. Apr. 13 11:51 Sh. E. June 16 9:18 Sh. E. 4:50 Ec. D. 8:20 Ec. D. Apr. 21 8:20 Ec. D. June 24 4:50 Ec. D. Ec. R. Apr. 21 13:10 Ec. R. June 24 10:53 Ec. R. 13:10 Ec. R. 10:53 SkyandTelescope.com April 2009 55 © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Celestial Calendar Crescent Moon Occults Venus On the morning of Wednesday, April Saturn’s Moons 22nd, skywatchers across North America except in the East and South can watch the Apr. 16 0 UT h waning crescent Moon pass across bril- Waning Moon liant crescent Venus. Occults Venus Seattle Calgary For much of the continent the occulta- April 22, 2009 Salt Lake City Apr. 1 tion happens after sunrise in daylight. If Los Angeles Denver 2 the air is clear you can fi nd the thin, dim Minneapolis Dallas Moon about 33° to the upper right of the Chicago 3 early-morning Sun, with Venus near the Toronto Mexico City 4 EAST WEST Moon’s edge. For the Far West the occulta- New York tion happens during morning twilight, 5 with the Moon and Venus low in the east. The apparent path of Venus behind the Moon 6 At locations where the sky is still fairly depends on where you are. The local horizon is dark, all you’ll need are your eyes. Where approximately downward here; celestial north 7 the sky is bright you’ll probably need bin- is to the upper left. 8 oculars or a telescope. Because of Venus’s signifi cant angular size, its disappearance 9% sunlit, while Venus (40 times smaller) 9 and reappearance will each be gradual, will be a 17% crescent. 10 Rhea taking 30 seconds or more. For local timetables: lunar-occultations The thin crescent Moon will be only .com/iota/planets/0422venus.htm. 11 12 Disappearance 13:30 13:50 Reappearance 14:00 13:50 13 13:40 13:20 13:40 13:50 13:10 13:00 14 Titan 13:30 13:30 12:50 13:40 12:40 13:20 13:20 15 Tethys Day Sunrise Day 13:30 Day Day 12:30 Twilight 13:10 13:20 13:10 16 Twilight 12:20 13:00 13:10 13:00 17 12:10 UT Twilight 12:50 Twilight 13:00 12:50 18 Enceladus 12:50 Sunrise 12:40 12:40 12:40 No No 19 12:30 occultation 12:30 UT 12:30 UT occultation GRAZE LINE 12:20 UT GRAZE LINE 20 Put a pencil dot on your location, and interpolate between the red curves to fi nd the Universal Times 21 (GMT) when Venus disappears and reappears for you on the morning of April 22nd. 22 The Lyrid Meteors 23 24 The April Lyrids are one of those meteor showers that usually don’t amount to much, 25 but you never know. In most years the shower produces no more than about 18 meteors visible per hour under ideal conditions. But some years have brought surprise 26 Dione outbursts of up to 90 per hour. 27 The peak this year should come in the early morning hours of Wednesday, April 22nd, when the Moon is a thin waning crescent and poses no problem. The shower’s 28 radiant is near Vega. This is the perspective point where the meteors would appear to 29 originate if you could see them coming from the far distance in space. The higher the radiant, the more meteors appear all over the sky. Watch whatever part of your sky is 30 darkest. May 1 56 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Ken Hewitt-White Suburban Star-Hop Two-Thirds of a Trio M65 and M66 in Leo are two of the brightest galaxies visible from suburban backyards. Leo, the lion, stands proudly high in the south invite comparison. M65 is magnitude 9.3 and almost 10′ on the moonless evenings of mid-April. The six-starred by 3′ in extent while M66 glows at magnitude 8.9 and is Sickle outlines the animal’s head with 1.4-magnitude about 9′ by 4′. Unfortunately, galaxies look much smaller Regulus at its base, while his hindquarters are repre- when light pollution renders their outer regions invisible. sented by a large right-angle triangle of 2nd- and 3rd- I suggest that you mount your search for M65 and M66 magnitude stars. In 2009 Saturn shines gloriously at when they’re highest — due south — and during very magnitude 0.7 a few degrees below the triangle. From clear weather. Your local skyglow is probably bad enough March through June the golden planet drifts in front of without thin clouds or haze worsening the situation. the Lion’s hind legs, a region of sky that contains several 1 2 The star-hop isn’t diffi cult. Begin at 3.3-mag- double stars and two bright nitude Theta (θ) Leonis, then drop 2° south- spiral galaxies. ward and slightly eastward to 5th-magnitude 73 Leonis. Lying just 1/ 3° apart, Center that star in a low-power eyepiece, then nudge your LEO the galaxies M65 and scope ¾° eastward to a 7th-magnitude star — the only M66 appear together in a one in the area. Now for the tricky part. Look for smudge medium- to high-power number one (M65) 18′ south of that star and smudge Saturn telescopic fi eld and thus number two (M66) 20′ east-southeast of M65. A 10th-mag- nitude star immediately northwest of M66 should help you establish that galaxy’s location. D +20° Observing from my suburban yard one moonless 2 Star magnitudes 3 4 5 6 night last spring, the side-by-side spirals materialized faintly but clearly in my 10-inch f/5.5 Dobsonian refl ector at 58×. In agreement with their listed magnitudes, M66 LEO glowed slightly more prominently than M65. Each galaxy 7 displayed a dense core surrounded by an elongated halo B Q +15° oriented roughly north-south. Increasing the magnifi ca- Denebola 3628 tion caused the smudges to blend into the skyglow. Push- 1–3 73 M66 M65 HOW FAR IS THE TRIO? 4 I +10° Sources list the distances of the galaxies that make up the Trio in Leo between 25 and 40 million light-years. It’s hard to measure how far any particular galaxy is with C a high degree of precision, but it’s likely that all three are the same distance from Earth, give or take a couple N Saturn million light-years. Otherwise, in order to appear so S (April 1, close together on the sky, they’d have lie along an almost 2009) +5° straight line pointing toward us. Galaxies tend to come in groups, so the rule of thumb VIRGO 5 is that if two or three galaxies look close together on the 83 sky, they probably are close together in space. Neverthe- T h h h B 11 40 m 11 20 m 11 00 m less, coincidences do occur. 58 April 2009 sky & telescope © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

SHELDON FAWORSKI / S&T: SEAN WALKER Messier 65 (right) and 66 are both classifi ed as barred spiral galaxies. M66’s bar is easy to see in this photo- graph — it’s the broad, straight, yellowish glow in the center that seems to anchor the two spiral arms. M65’s bar is harder to discern because this galaxy is tilted more edgewise to our line of sight. ing my luck, I went for the oval fuzzies with my 4¼-inch stars glow beautifully red in my REU PROGRAM / NOAO / AURA / NSF f/6 refl ector. Both galaxies surfaced at 54×, but they were 10-inch. at the threshold of vision. Again, extra magnifi cation 4 For a true binary, follow the produced no improvement. zigzag another 2° southeast- NG NG NGC 3628 (top), the third member CC 36362828 ( (totop)p), hththee hththiirirddd meme bmbmberer 3 For bonus points, try spotting NGC 3628 located ward to yellowish Iota (ι) Leonis. of the Trio in Leo, is hard to see from 36′ north of M66. This edge-on galaxy turns our Provided the atmospheric seeing suburban backyards because of its tandem into the well-known “Trio in Leo.” Ah, but there’s is rock-steady, I can split Iota into low surface brightness. Note how this a catch. NGC 3628 is offi cially magnitude 9.5, just a hair 4.1- and 6.7-magnitude dots just 1.7″ galaxy’s broad, dark dust lane nearly fainter than M65. But its light is spread out over an area apart at 186× in my 4¼-inch. blocks its bright core from view. measuring 15′ by 3′, so the object suff ers from low surface 5 One last treat: From Iota, brightness. NGC 3628 certainly appears much dimmer trend southward for nearly 8°, past 4th-magnitude than its Messier neighbors. From my suburban backyard Sigma (σ) and nearby Saturn, to 5.1-magnitude Tau (τ) last spring, I glimpsed the ghostly spindle in my 10-inch Leonis. Yellow-orange Tau has a 7.5-magnitude binocular but not in my 4¼-inch. Away from town, the smaller companion 89″ to the south. Only 20′ west-northwest of scope pulls in the full Trio every time. Tau is the telescopic binary 83 Leonis, whose 6.6- and 7.5- Sometimes our deep-sky searches sweep up pretty stars magnitude components lie 28.6″ apart. Tau and 83 Leonis we’ve never seen before. Using low magnifi cation, aim together make a delightful, low-power “double double” in your scope below 73 Leonis and you’ll see that it anchors any telescope. ✦ a 1½°-long zigzag of a half dozen 7th- and 8th-magnitude stars. Marking the second-to-last link in the chain is a pair Ken Hewitt-White’s favorite pastime is observing of unrelated 7.6- and 8.8-magnitude stars 83″ apart. These galaxy groups, near and far. SkyandTelescope.com April 2009 59 © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Sue French Deep-Sky Wonders The Dry Bear Every corner of Ursa Major is chock-a-block with galaxies. The Bear, that sees star setting after star She looks as though she’s lying on her back with her toes In the blue brine, descends not to the deep. brushing the zenith — a perfect time for Bear watching. — William Cullen Bryant, The Order of Nature Let’s start at Upsilon (υ) Ursae Majoris, the star at the top of the Bear’s foreleg. Through my 4.1-inch (105-mm) This ursine verse refers to the circumpolar refractor at 28×, Upsilon shares the fi eld of view with the nature of the Great Bear, ever visible as she nightly prowls galaxy NGC 2950, located 1.1° west and 11′ south of the around the North Star. But you have to be pretty far north star. At such a low power, the galaxy is very small and before Ursa Major does not at least wet her toes in the faint, but it displays a brighter center. At 87× I can see oceans of the world. At my latitude of 43° north, only that NGC 2950 presents us with an oval profi le canted her northernmost toe remains forever dry. To keep her northwest, and its core harbors a bright, starlike nucleus. southernmost toe from splashing in the briny blue, you’d With my 10-inch refl ector at 213×, NGC 2950 covers 1¼′ have to be north of 58.5°. During the evening at this time × ¾′ and shows a 14.9-magnitude star near the midpoint of the year, however, the Bear snoozes high in the north. of its southwestern fl ank. This star sits at the south-south- NGC 2820 NGC 2814 IC 2458 NGC 2805 Austrian astrophotographer Bernhard Hubl’s image captures all four galaxies in the group Holmberg 124. SkyandTelescope.com April 2009 61 © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Deep-Sky Wonders eastern end of a straight, ¾′-long line that it makes with in my little refractor even at 17×. At 47× its east-west oval two others, magnitudes 15.4 and 15.5. But I didn’t spot grows brighter toward a stellar nucleus. A magnifi cation them. Can you? If so, the 15.0-magnitude star ½′ west- of 87× gives a prettier view, with a 10th-magnitude star northwest of the northernmost star will turn the line into off the galaxy’s west-northwestern edge and a faint star a stubby hockey stick. close to its east-northeastern edge. If I push my scope The simple appearance of this galaxy through the northwest, NGC 2742 shares the 53′ fi eld of view with a eyepiece belies its complicated structure. NGC 2950 is a little room to spare. It’s similar to NGC 2768 in shape and double-barred lenticular (lens-shaped) galaxy. The two orientation but is smaller and has a more uniform surface bars rotate at diff erent speeds, and recent studies suggest brightness. NGC 2742 is accompanied by a deep-yellow that the small inner bar may rotate in the opposite direc- star northwest and a little triangle of faint stars southwest. tion from the large outer bar and the galaxy’s large-scale NGC 2950, NGC 2768, and NGC 2742 lie at similar disk. It seems unlikely that such a bar would survive very distances of about 65 million light-years. long unless the galaxy’s inner disk is also counterrotating. Dropping about a degree south of NGC 2742 takes you Next we’ll visit NGC 2768, which lies halfway between to a 6th-magnitude star, from which you can hop 1.8° Upsilon and Omicron (ο) Ursae Majoris, the star that west to another. NGC 2685, the Helix Galaxy, rests 27′ marks the Great Bear’s nose. This galaxy is faintly visible southeast of the second star. It’s a very faint northeast- Left: Can you see both of NGC 2950’s bars in this image from the Sloan Digital Sky Survey? Right: This deep image, also from the Sloan Digital Sky Survey, shows NGC 2681 (described on page 64) to be a subtle but beautiful barred lenticular galaxy that’s aimed face-on at Earth. 62 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

southwest oval through my 4.1-inch refractor at 28×, and h h h a faint star roosts north of its northeastern tip. At 87× it’s +65° 9 30 m 9 00 m 8 30 m 1½′ long and grows slightly brighter toward its center. P 1 2 IC 2458 At 45 million light-years, the Helix (pictured on page 2814 2 3 2820 P 4 64) is one of the nearest polar-ring galaxies. A polar-ring 2805 T 23 5 galaxy exhibits a disk or ring of gas, dust, and stars that’s Star magnitudes 6 nearly perpendicular to the disk of the host galaxy. The 7 ring is thought to arise as the result of merger with or 8 accretion of material from a neighboring galaxy. Through O 16 my 10-inch refl ector at high power, the only suggestion Muscida +60° 2742 of the Helix Galaxy’s polar ring is a somewhat greater central width than I might expect otherwise. My 14.5-inch U 2768 scope very faintly shows stubby protrusions tipped a bit 2950 2685 clockwise from a perpendicular to the main galaxy, with the stub on the northwestern side more obvious. URSA MAJOR Climbing northward takes us to an interesting quartet of galaxies, Holmberg 124 (see page 61). The largest mem- 17 ber of the group is NGC 2805, 1.2° east-northeast of Tau (τ) Ursae Majoris. This face-on spiral has very low surface +55° brightness, and observers armed with small telescopes URSA MAJOR may only be able to spot its tiny, brighter core. Through 18 my 10-inch refl ector at 170×, this ghostly galaxy appears irregularly round and 4′ to 5′ across. It’s bracketed by a 41321 pair of fairly bright stars, magnitudes 9 and 10, while a 26 12th-magnitude star guards its northwestern edge. 15 2681 Sharing the fi eld of view, NGC 2814 is perched 10.5′ Q 2841 north-northeast of its bigger companion and has an 11th- magnitude star near its southern tip. This edge-on spiral has a signifi cantly dimmer total magnitude than NGC seen edge on and appear at least seven times longer than 2805 does, but its light is confi ned to a much smaller area, wide. Through my 10-inch scope, the slender form of resulting in considerably higher surface brightness. My NGC 2820 cuts east-northeast to west-southwest for 2½′ scope shows a very faint, north-south slash nearly 1′ long. and joins the fi eld with its neighbors. NGC 2820 is a bit more obvious than NGC 2814 and The Holmberg galaxies are the most distant in our centered only 3.7′ to its east. NGC 2820 is another edge-on tour, approximately 76 million light-years away. I missed spiral, thin enough to be listed in the Revised Flat Galaxy the fi nal member of the group, faint little IC 2458, when Catalogue (Karachentsev et al., 1999). RFGC entries are surveying the area with my 10-inch scope. Can you spot disk-like galaxies with little or no central bulge that are this galaxy dangling from the western tip of NGC 2820? SkyandTelescope.com April 2009 63 © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Deep-Sky Wonders Ken Crawford’s amazingly detailed image of NGC 2685 shows why this is known as the Helix Gal- axy. Right: Even through a modest 8-inch telescope, Finnish stargazer Jere Kahanpää was able to see and sketch the essential needle-and-cocoon shape of the Helix Galaxy. Now we’ll plunge southward to 15 a fairly small, round, faint bit of mist with Ursae Majoris, the trailhead for our fi nal a brighter center. At 47× I see a pair of two deep-sky wonders. The double star faint stars just off the west-northwestern Struve 1321 (Σ1321) lies halfway between edge. Through my 10-inch scope at 220×, and a shade east of a line connecting 15 the galaxy’s starlike nucleus gleams in a and 18 Ursae Majoris, which fi t in the slightly lumpy core, both cloaked in a soft same fi eld of view through a fi nderscope. gray mantle 3′ across with a faint star nuz- Its matched components are split at 17× zling its eastern border. in my little refractor, which shows a lovely Sitting only 38 million light-years away, east-west pair of golden-orange suns. NGC 2681 is the nearest galaxy in our Next place 15 Ursae Majoris a little deep-sky tour of the dry Bear. ✦ north of center in your telescope’s fi eld of view and sweep 2.4° west to the galaxy You can reach Sue French at scfrench@ NGC 2681. My 4.1-inch scope at 17× shows nycap.rr.com. Nine Galaxies and One Double Star Typepe Object Ty Magnitude Size/Sep.Size/Sep. RA Dec.Dec. Gala 2.7′ × 1.8′ 9 42.6′ × 1.8′ NGC 2950 Galaxy xy 10.9 2.7 h m +58° 51′+58° 51′ NGC 2768 Gala 9.9 6.4′ × 3.0′ 9 11.66.4′ × 3.0′ h m +60° 02′° 02′ Galaxy xy +60 h m Galaxy NGC 2742 Galaxy 11.4 3.0′ × 1.5′ 9 +60° 29′60° 29′ + 07.6 3.0′ × 1.5′ 4.6′ × 2.5′ 8 Galaxy NGC 2685 Galaxy 11.3 4.6′ × 2.5′ h 55.6 m +58° 44′+58° 44′ 6.3′ × 4.8′ 9 20.33′ × 4.8′ Galaxy xy NGC 2805 Gala 11.0 6. h m +64° 06′+64° 06′ + NGC 2814 Galaxy 13.7 1.2′ × 0.3′ h 21.2 m +64° 15′64° 15′ Galaxy 1.2′ × 0.3′ 9 h m + 4.3′ × 0.5′ Flat Galaxy NGC 2820 Flat Galaxy 12.8 4.3′ × 0.5′ 9 +64° 15′64° 15′ 21.8 IC 2458 Galaxy Galaxy 15.0 0.5′ × 0.2′ 9 21.55′ × 0.2′ h m +64° 14′+64° 14′ 0. + Double star Σ1321 Double star 7.8, 7.9 17″″ h 14.4 m +52° 41′52° 41′ 17″ 9 Galaxy xy NGC 2681 Gala 10.3 3.6′ × 3.3′ 8 53.53.6′ × 3.3′ h m +51° 19′+51° 19′ Angular sizes and separations are from recent catalogs. Visually, an object’s size is often smaller than the cataloged value and varies according to the aperture and magnifi cation of the viewing instrument. Right ascension and declination are for equinox 2000.0. © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Ultra-Wide-Field Imaging © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

© 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

Ultra-Wide-Field Imaging Imaging the Orion-Eridanus Superbubble dennis di cicco & sean walker From the night sky’s brightest star Commercially available cameras and and most-illustrious nebulae, to large software allow today’s amateurs to sweeps of glowing hydrogen that few readers have ever seen before, there’s create unprecedented images. a tremendous range of deep-sky detail visible on the previous two pages. But All images created by Dennis di Cicco & Sean Walker that’s not surprising given the vast area of sky involved. Centered roughly Even astrophotographers familiar with wide-fi eld views may QUICK TOUR on the constellation Orion, the view need a moment to orient themselves within the mosaic, stretches 65° along the celestial equator since prominent nebulosity appears in areas usually thought to be devoid of deep-sky objects. Dominating the bottom center of the image is the constel- from Monoceros at left to Eridanus at lation Orion and Barnard’s Loop, the distinctive crescent-shaped nebula right. It’s only part of a mosaic that around the celestial giant’s Sword. The Orion and Horsehead nebulae, though two of the most famous deep-sky objects in the heavens, are almost we created earlier this year. Covering lost in the general tangle of nebulosity inside the arc of Barnard’s Loop. more than 4,000 square degrees, the A large circular glow in the head of Orion, enveloping the 3rd-magni- full view records almost 10% of the sky tude star Lambda (λ) Orionis, carries the prosaic designation Sh2-264, but is popularly known as the Angelfi sh Nebula. To its lower left is Betelgeuse, visible from Earth. one of but a few stars standing out prominently in this view. Another is Just a few years ago, images like Sirius, the brightest nighttime star, near the lower left edge of the fi eld. Like pearls on a necklace, large and small patches of glowing hydrogen this would have been all but impossible stretch along a band running from Canis Major at lower left to Auriga at to produce. The fact ours was made top center. They roughly defi ne the plane of our galaxy in what we north- with readily available equipment and erners know as the winter Milky Way. The bright complex in Perseus at upper right includes the California Nebula, though the state gets a note- image-processing software emphasizes worthy border revision because of the faint nebulosity recorded here. The some of the rapid advances taking Pleiades, dwarfed by the scale of the mosaic, are prominent along the right side of the image. The dazzling star Aldebaran, in the familiar V-shaped place in astrophotography. Further- asterism forming the head of Taurus, lies to the right of the image’s center. more, our exposures were made from Beneath the Pleiades, running along an imaginary north-south line h a suburban-Boston backyard that’s at roughly 4 right ascension, is a sinuous nebula known as the Eridanus Loop. The 30°-tall feature, though prominent in this view, is rarely photo- surrounded by some of the world’s most graphed and likely to be new to many amateurs. Even less familiar is the light-polluted skies. rippling veil of nebulosity permeating the region. Facing page: This mosaic covers nearly 10% of the visible sky, capturing more than 4,000 square degrees along the plane of our Milky Way Galaxy running from Canis Major at lower left to Auriga at top center. Dominating the lower half of the fi eld, the huge Orion-Erida- nus Superbubble was carved from the interstellar medium by forces originating within the Orion OB 1 Association of hot, young stars. 68 April 2009 sky & telescope © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved. © 2

The Orion-Eridanus Superbubble Eridanus Loop marks another side. This is also the sec- The Orion Nebula is famous for being a stellar nursery, tion closest to us, at an estimated distance of about 600 but the whole central area of the constellation is a mas- light-years. Barnard’s Loop, on the other hand, is thought sive star-formation region. Collectively called the Orion to be about 1,300 light-years away. OB 1 Association, it comprises several subgroups of hot, For those who want to learn more about this intensely young stars. At the upper right of Orion’s Belt, the oldest studied region, star-formation expert John Bally (Univer- and closest subgroup, Orion OB 1a, has stars roughly 8 sity of Colorado) has written an overview in the Handbook to 12 million years old, which lie about 1,100 light-years of Star Forming Regions: Volume I, The Northern Sky. away. The Orion Nebula is part of the youngest subgroup, The new book is part of the Astronomical Society of the Orion OB 1d, with stars less than 2 million years old and Pacifi c’s Monograph Publications, and it’s available elec- lying about 1,400 light-years away. tronically on the ASP’s website (astrosociety.org). Stellar winds and the aftermath of an estimated 10 to 20 supernova explosions within the Orion OB 1 Associa- Work in Progress tion during the past 12 million years have blown a large Our mosaic is a work in progress. Indeed, the view here bubble in the surrounding interstellar medium. Recog- started out merely as a map to locate the extent of the nized since the 1970s, it’s known as the Orion-Eridanus Orion-Eridanus Superbubble that we could record. We’re Superbubble. In the red light of hydrogen-alpha emission currently working on a new version with images that are (656.3 nanometers wavelength), Barnard’s Loop is the deeper and have better resolution. brightest part of the bubble. Some 40° to its west, the The view here, however, is made from 15 frames total- SkyandTelescope.com April 2009 69 © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.

Ultra-Wide-Field Imaging ing more than 50 megapixels. We acquired them mainly with an SBIG STL-11000 CCD camera, Astrodon 3-nm Hα fi lter, and 80-mm Hasselblad medium-format lens. But there are also exposures made with a Baader 7-nm Hα fi lter and 50-mm Hasselblad lens. We did various aspects of the image processing with MaxIm DL, CCD- Stack, RegiStar, and Adobe Photoshop. Although we’ve lost track of the mosaic’s total expo- sure time (because of frames rejected due to clouds), the initial exposures exceed 40 hours. The original is a 100-megabyte fi le, which contains more detail than we can show here. For readers who want a better look, we’ve placed a version on our website (skyandtelescope. com/skytel). We made it a 3-megabyte fi le by halving the original resolution and saving it in jpeg format. We’re sure there will be an ever-increasing number of spectacular and unusual views of the night sky as amateurs continue to exploit new digital tools. Tech- niques that weren’t even dreamed of by photographers working in darkrooms are now accomplished with just a few mouse clicks. There’s never been a better time for astrophotographers to let their imaginations soar. ✦ To emphasize the full extent of the mosaic, the authors created this view by ghosting its features onto a wide-fi eld starscape taken in the same light-polluted backyard where the exposures Sky & Telescope’s resident astrophotographers, Dennis di for the mosaic were made. Cicco and Sean Walker, collaborate on many projects. 70 April 2009 sky & telescope © 2 © 2009, New Track Media, LLC. All Rights Reserved. 009, New Track Media, LLC. All Rights Reserved.