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STELLAR CHRONICLE 5 . INDEX 1. Editorial………………………………………………...………………6 2. Aryabhatta-The inspirational Remainder............................................7 3. James Webb Space Telescope (JWST).................................................25 4. Black Holes: A Bizarre Myth ................................................................23 5. Ellipses to the Infinity............................................................................28 6. And the Journey Still Continues...........................................................36 7. Exoplanets and the Possibility of Life Beyond the Earth…………..37 8. Types of Stars..........................................................................................61 9. A brief introduction to Radio Astronomy ...........................................63 10. Diary of my Weird Dreams!.................................................................69 11. Are we Alone in this Universe, or are there any Aliens? ...................72 12. Scope of Sounding Rockets in plasma related researches................74 13. The Airglow and Electroglow of Outer Planets.................................78 14. Ionospheric Studies...............................................................................80 15. A brief study on Plasma Bubble..........................................................82 16. A Glance through ‘22 Events...............................................................86 17. Sky Safari: Night Sky Photography……….…...……………..……..90 18. Creative Space………………………….……………………………..95 UL SPACE CLUB

STELLAR CHRONICLE 6 . EDITORIAL With the launch of the third edition of the “STELLAR CHRONICLE'' a Halfyearly EMagazine, the UL Space Club embarked on an ambitious voyage. A voyage fuelled by the enormous enthusiasm and youthful exuberance of its members and well-wishers. The first and second issues were well received. Now we are ready with the third issue. The focus continues to be the promotion of creative abilities of the club members, especially their skills to assimilate and express information, ideas and happenings in the stellar domain, in the written form, in their own distinct style. The issue starts with an inspirational story of Aryabhata Satellite which was India’s first artificial satellite written by Dr V Jayaraman. We have tried to include articles based on the latest researches and findings in the fields of space science and technology. Also there is Dr M R Sivaraman giving a perspective of James webb space telescope which have included in our cover page too. Student articles on Radio Astronomy, Blackholes, Astronomical & Astronomic events follow, as also the standard features of Sky Safari and Creative Space. Paper works of UL Space Club students as a part of their sounding rocket project is also a part of this edition. I am sure that we are nowhere near perfection. It is a work in progress. So kindly bear with us! As always, we look forward to your critiques and applause. That will energise us in the journey ahead. Happy reading! Jayaram Kolangara Chief Editor Stellar Chronicle UL SPACE CLUB

STELLAR CHRONICLE 7 . Aryabhatta-The Inspirational Remainder Dr. V. Jayaraman, Former Director, NRSC, ISRO It is April 19, 2021 as I sit in front of my laptop to bring out a few of my thoughts for the Memoir to be brought by the Pensioners’ Forum. For us in Bangalore, the month of April always brings out happy days with tabebuias painting the streets pink, yellow and lavender, with netizens flooding the social media with photos of the beautiful blooms; and Ugadi & other festivities bringing togetherness, however limited they are in these depressive days of COVID; and anticipation of pre-monsoon showers after the scorching month of March. More than that, for the ISROvites, the month of April brings the sweet memories of our first satellite ARYABHATA. It was on April 19, 1975 that ARYABHATA roared into the sky atop an Intercosmos rocket from Kapustin Yar Cosmodrome in the then USSR. It is now 46 years since the launch of ARYABHATA, but still it remains as an inspirational reminder for all of us! Aryabatta- Sowing the seed for ISRO culture Dr Vikram Sarabhai once said: “The early beginning of any institution is crucial, and the culture (or lack of it) brought by the first entrants plays a significant role in establishing norms, procedures and practices of any organisation”. The way the initial seeds were sown in ISRO’s early days, be it in ARYABHATA or for that matter in SLV which followed closely, this building of UL SPACE CLUB

STELLAR CHRONICLE 8 . Team ISRO spirit was very evident. For example, ARYABHATA even today continues to evoke nostalgic memories of the near ideal environment and encouragement the organisation could provide for fostering scientific and technological excellence even in those days of inadequate infrastructure and inexperienced hands. It is not an easy task by any means! Space endeavour is a complex, high risk, interdisciplinary field, with many large systems working together seamlessly, and expecting a consistent high quality performance in extreme space environments. It calls for an intricate organisational arrangement and professional integrity and performance as an integrated team working with transparency and missionary zeal. Over time, this model defines the basic characteristics of the organisation itself. As said elsewhere Project ARYABHATA paved the way for this evolution of what is famously recognised today as ISRO Culture. Basically, this ISRO Culture imbibed and evolved over time essentially embodies the lofty ideals of constructive Intellectual irreverence, organisational discipline, and innate humanism among many other things as fervently advocated by Dr Vikram Sarabhai and Prof Satish Dhawan. Constructive Intellectual Irreverence The basic tenet of progress in any field is essentially propelled by the inquisitiveness of the human intellect, and the eagerness with which one pursues the quest for knowledge in a given environment; and when encouraged proactively it produces newer thoughts and innovative ideas. It is more so in high technology areas where the developments are dynamic and fast changing. Institutions of advanced technologies such as ISRO recognise that this inquisitive learning is a continuous process and is not by any means unidirectional – knowledge and wisdom do not flow only from seniors to juniors. Further, they do recognise and appreciate the very need for learning communities to be well grounded in an ethos of perfect understanding and mutual respect even among those who don’t agree with each other. Thus, this intellectual irreverence can be constructive in respectfully differing viewpoints and showing the dissension on the basis of solid logical and cogent arguments, empirical and experimental findings while maintaining at the same time the larger perspective of team spirit in mind. Constructive intellectual irreverence, thus, underlines the willingness to break the intellectual boundaries and conventional/ traditional wisdom while still making efforts to understand and be respectful to those very ideas even as new innovative ideas are articulated. Yes, it may be easier to talk about the building an environment of intellectual UL SPACE CLUB

STELLAR CHRONICLE 9 . irreverence in an institution, rather than the challenges of fostering one in a real life situation that too from scratch. It is to the credit of ISRO that right from its early infant days, this spirit of constructive intellectual irreverence was encouraged with Project ARYABHATA providing the major testing ground for what is proudly acclaimed today as ISRO Culture. Credit should go to Prof Satish Dhawan and Prof UR Rao for making it a reality. ISRO Culture ISRO Culture continues to encourage productive conflicts and constructive criticisms (from both internal and external) with transparent peer review mechanisms. Questioning assumptions and expressing ideas freely without hesitation are the hallmarks of this healthy environment. In this constructive irrelevance environment encouraged in ISRO, it is common to see a youngest engineer in terms of organisational hierarchy debating on equal terms with a veteran senior space scientist with pure technical judgement as the only matter of discussion. As pointed out earlier, this recognition that the knowledge learning process is not unidirectional brings in a mutual learning experience, grounded in an ethos of respect, and appreciation of the inherent merit of the arguments rather than based on mere hierarchy. Thus, ISRO exhibits extraordinary professional maturity and resilience to reflect, review and learn lessons dispassionately - from both failures and successes-before a final conclusion or decision is arrived at.Once such a decision is taken based on the analysis and extensive intellectual discussions and constructive criticisms, the Team ISRO whole heartedly accepts the final decision and traverses through the chosen path with grit, determination, discipline and full devotion and dedication in a mission mode till the goal is achieved. Yet another stellar characteristic inherent in ISRO culture is the extraordinary care the organisation takes about its talent management. Besides providing & encouraging a conducive, creative, challenging environment for the younger generation, sustaining their continued curiosity and interest, the additional care taken by ISRO in providing career promotion opportunities; and recognizing & rewarding talent by awarding additional emoluments to the meritorious as well as providing a comprehensive medical care for all its employees and their families by approved schemes stand out as exemplary. In this context too, ARYABHATA set an example in those early days when none of these schemes were in vogue. Even now those associated with ARYABHATTA recall fondly the vitamin tablets given with the nutritious refreshments at the canteen to the employees working late in the evenings to keep the body and mind together. A simple gesture but which UL SPACE CLUB

STELLAR CHRONICLE 10 . conveyed the care organisation showered on its dedicated team. In return, the Team members worked with extraordinary missionary zeal with individuals exhibiting their innate drive toward self-actualization – a state of achieving at his or her highest level of capability. A win-win situation for the organisation and the employees! Such a healthy environment fosters mutual respect and confidence and paves way for sustaining long term dividends for both the organisation and its employees. The Team ISRO today With this ever-binding spirit, ISRO today is a sublime blend of youth and maturity, providing a judicious mix of enthusiasm and inventive power of the youth and expertise and wisdom of elders auguring well for the future of the Organisation. Such an organisational spirit is also sustained due to (i) continued political will at national and state level leadership to support the space programme irrespective of whichever political party comes to power; (ii) the professional leadership at organisational level in ISRO/DOS that encourages a conducive, creative, challenging environment for the younger generation for sustaining their continued curiosity and at the same time, ensuring its adherence to the larger national developmental goals; and finally (iii) the everlasting public trust in the programme, an essential component in a democracy. With such enormous goodwill and commitments, ISRO stands out today as a vibrant, self-reliant and user driven enterprise providing cost effective operational services in areas crucial to national development; deriving its sustenance from indigenous industry, academia, and international cooperation; and in the process making it a visible symbol of the resurgent India. In this ISRO’s success on a shoe-string budget story, the spirit of ARYABHATA will always remain as the inspirational reminder for years to come. UL SPACE CLUB

STELLAR CHRONICLE 11 . James Webb Space Telescope (JWST) Dr. M.R.Sivaraman, Ex Scientist, Space Application Centre, ISRO Introduction: The James Webb Space Telescope (JWST) is a space telescope developed by NASA with contributions from the European Space Agency (ESA), and the Canadian Space Agency (CSA). The telescope is named after James E. Webb, who was the administrator of NASA from 1961 to 1968 and played an integral role in the Apollo program. It is intended to succeed the Hubble Space Telescope as NASA's flagship mission in astrophysics. JWST was launched on 25 December 2021 on Ariane flight VA256. It is designed to provide improved infrared resolution and sensitivity over Hubble, and will enable a broad range of investigations across the fields of astronomy and cosmology, including observations of some of the most distant events and objects in the Universe such as the formation of the first galaxies, and allowing detailed atmospheric characterization of potentially habitable exoplanets. On 16th March, 2022, the James Webb Space Telescope's main mirror was fully aligned and has been performing even better than it had been designed to do, NASA officials revealed in a news conference held virtually. An image taken by the James Webb Space Telescope during its alignment process shows galaxies and stars in the background. With all its gear deployed, aligned and cooled down, Webb will be able to see the first stars that sprung up in the nascent universe only a few hundred million years after the Big Bang. In this article, I have tried to bring out some details on JWST and a brief mention of materials used for making the Lens. Objectives: The James Webb Space Telescope has four key goals: 1. Search for light from the first stars and galaxies that formed in the Universe after the Big Bang 2. Study the formation and evolution of galaxies 3. Understand the formation of stars and planetary systems 4. Study planetary systems and the origins of life. UL SPACE CLUB

STELLAR CHRONICLE 12 . These goals can be accomplished more effectively by observation in near-infrared light rather than light in the visible part of the spectrum. For this reason, JWST's instruments will not measure visible or ultraviolet light like the Hubble Telescope but will have a much greater capacity to perform infrared astronomy. JWST will be sensitive to a range of wavelengths from 0.6 to 28 μm (corresponding respectively to orange light and deep infrared radiation at about 100 K or −173 °C). JWST may be used to gather information on the dimming light of star KIC 8462852, which was discovered in 2015 and has some abnormal light-curve properties. Structure and Components of JWST: The components of JWST are explained in detail in this section. 1. Optical Telescope: The optical telescope element (OTE) of the James Webb Space Telescope has a three-mirror anastigmat design, consisting of a primary, secondary, and tertiary mirror. Figure 1: The Structure of an Optical Telescope The design of the OTE was chosen to provide a high-quality image to the integrated science instrument module (ISIM), which houses the Webb science instruments.The primary mirror of JWST, the Optical Telescope Element, consists of 18 hexagonal mirror segments made of gold-plated beryllium, which combine to create a 6.5 m (21 ft)-diameter mirror – considerably larger than UL SPACE CLUB

STELLAR CHRONICLE 13 . Hubble's 2.4 m (7.9 ft) mirror. The mirrors are made of beryllium because it has an extremely small variation in its coefficient of thermal expansion over temperatures of 30-80K. This makes the telescope optics intrinsically stable for small temperature variations. A thin gold coating provides high infrared reflectivity over a broad spectral bandpass, from 0.6 to 29 μm. They are arranged in two rings around the center, resulting in a quasi-hexagonal shape with a 6.5m flat-to-flat diameter. The collecting area is 25 square meters (equivalent to approximately a 6 m circular primary). The segments are attached to a stable, rigid, graphite-composite backplane structure. Each segment is relatively stiff and will be figured to have the correct off-axis surface at the nominal cryogenic 40K temperature of the primary. Each segment has six actuators to adjust its position and a seventh to change its radius of curvature (focal length). Figure 2: JWST Primary Mirror EDU coated in gold and JWST Flight Tertiary Mirror The secondary mirror has 6-degrees of adjustments for collimation and overall focus. Unlike the Hubble telescope, which observes in the near ultraviolet, visible, and near-infrared (0.1–1.0 μm) spectra, JWST will observe in a lower UL SPACE CLUB

STELLAR CHRONICLE 14 . frequency range, from long-wavelength visible light (red) through mid-infrared (0.6–28.3 μm). This will enable it to observe high-redshift objects that are too old and too distant for Hubble. The telescope must be kept very cold to observe in the infrared without interference, so it will be deployed in space near the Sun-Earth L2 Lagrange point, about 1.5 million kilometers (930,000 mi) from Earth (0.01 au – 3.9 times the average distance to the Moon). A large sun shield made of silicon- and aluminium-coated Kapton will keep its mirror and instruments below 50 K (−223 °C; −370 °F). The segments are attached to a stable, rigid, graphite-composite backplane structure. Each segment is relatively stiff and will be figured to have the correct off-axis surface at the nominal cryogenic 40K temperature of the primary. Each segment has six actuators to adjust its position and a seventh to change its radius of curvature (focal length). The secondary mirror has 6-degrees of adjustments for collimation and overall focus. Figure 2 shows the images of the Primary mirror segment EDU and the flight tertiary mirror coated in gold. At launch, the two \"wings\" of the primary mirror are folded to allow it to fit in the fairing of the Ariane launch vehicle. Similarly, the secondary mirror is attached to a deployable tripod support structure, which latches into position after launch. The Integrated Science Instrument Module (ISIM) is a framework that provides electrical power, computing resources, cooling capability as well as structural stability to the Webb telescope. It is made with a bonded graphite-epoxy composite attached to the underside of Webb's telescope structure. The ISIM holds the four science instruments and a guide camera. 2. NIRCam: NIRCam (Near InfraRed Camera) is an infrared imager that will have a spectral coverage ranging from the edge of the visible (0.6 μm) through the near-infrared (5 micrometers). There are 10 sensors each of 4 megapixels. NIRCam will also serve as the observatory's wavefront sensor, which is required for wavefront sensing and control activities. NIRCam was built by a team led by the University of Arizona, with principal investigator Marcia J. Rieke. The industrial partner is Lockheed-Martin's Advanced Technology Centre in Palo Alto, California. UL SPACE CLUB

STELLAR CHRONICLE 15 . Figure 2: JWST Primary Mirror EDU coated in gold and JWST Flight Tertiary Mirror 3. NIRSpec: NIRSpec (Near InfraRed Spectrograph) will also perform spectroscopy over the same wavelength range. It was built by the European Space Agency at ESTEC in Noordwijk, Netherlands. Figure 2: JWST Primary Mirror EDU coated in gold and JWST Flight Tertiary Mirror The leading development team includes members from Airbus Defence and Space, Ottobrunn and Friedrichshafen, Germany, and the Goddard Space Flight Center; with Pierre Ferruit (École normale supérieure de Lyon) as NIRSpec project scientist.The NIRSpec design provides three observing modes: a low-resolution mode using a prism, an R~1000 multi-object mode, and an R~2700 integral field unit or long-slit spectroscopy mode. Switching of the modes is done by operating a wavelength pre-selection mechanism called the Filter Wheel Assembly and selecting a corresponding dispersive element (prism UL SPACE CLUB

STELLAR CHRONICLE 16 . or grating) using the Grating Wheel Assembly mechanism. Both mechanisms are based on the successful ISOPHOT wheel mechanisms of the Infrared Space Observatory. The multi-object mode relies on a complex micro-shutter mechanism to allow for simultaneous observations of hundreds of individual objects anywhere in NIRSpec's field of view. There are two sensors each of 4 megapixels. The mechanisms and their optical elements were designed, integrated, and tested by Carl Zeiss Optronics GmbH of Oberkochen, Germany, under contract from Astrium. 4. MIRI: MIRI (Mid-InfraRed Instrument) will measure the mid-to-long-infrared wavelength range from 5 to 27 μm. It contains both a mid-infrared camera and an imaging spectrometer. MIRI was developed as a collaboration between NASA and a consortium of European countries and is led by George Rieke (University of Arizona) and Gillian Wright (UK Astronomy Technology Centre, Edinburgh, Scotland, part of the Science and Technology Facilities Council (STFC)). Figure 2: JWST Primary Mirror EDU coated in gold and JWST Flight Tertiary Mirror MIRI features similar wheel mechanisms to NIRSpec which are also developed and built by Carl Zeiss Optronics GmbH under contract from the Max Planck Institute for Astronomy, Heidelberg, Germany. The completed Optical Bench Assembly of MIRI was delivered to Goddard Space Flight Centre in mid-2012 for eventual integration into the ISIM. The temperature of the MIRI must not exceed 6 K (−267 °C; −449 °F): a helium gas mechanical cooler sited on the warm side of the environmental shield provides this cooling. UL SPACE CLUB

STELLAR CHRONICLE 17 . 5. FGS/NIRISS: FGS/NIRISS (Fine Guidance Sensor and Near-Infrared Imager and Slitless Spectrograph), led by the Canadian Space Agency under project scientist John Hutchings (Herzberg Astronomy and Astrophysics Research Centre, National Research Council), is used to stabilize the line-of-sight of the observatory during science observations. Measurements by the FGS are used both to control the overall orientation of the spacecraft and to drive the fine steering mirror for image stabilization. The Canadian Space Agency is also providing a Near-Infrared Imager and Slitless Spectrograph (NIRISS) module for astronomical imaging and spectroscopy in the 0.8 to 5 μm wavelength range, led by principal investigator René Doyon at the Université de Montréal. Because the NIRISS is physically mounted together with the FGS, they are often referred to as a single unit; however, they serve entirely different purposes, with one being a scientific instrument and the other being a part of the observatory's support infrastructure. Figure 2: JWST Primary Mirror EDU coated in gold and JWST Flight Tertiary Mirror NIRCam and MIRI feature starlight-blocking coronagraphs for observation of faint targets such as extrasolar planets and circumstellar disks very close to bright stars. The infrared detectors for the NIRCam, NIRSpec, FGS and NIRISS modules are being provided by Teledyne Imaging Sensors (formerly Rockwell Scientific Company). The James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM) and Command and Data Handling (ICDH) engineering team use SpaceWire to send data between the science instruments and the data-handling equipment. UL SPACE CLUB

STELLAR CHRONICLE 18 . Details of Launch and Deployment : The James Webb telescope was successfully launched on 25th December, 2021. The telescope is deployed on its 29-day, million-mile journey out to the second Lagrange Point (L2). A Lagrange point is a location in space where the combined gravitational forces of two large bodies, such as Earth and the sun or Earth and the moon, equal the centrifugal force felt by a much smaller third body. The interaction of the forces creates a point of equilibrium where a spacecraft may be \"parked\" to make observations. These points are named after Joseph-Louis Lagrange, an 18th-century mathematician who wrote about them in a 1772 paper concerning what he called the \"three-body problem.\". These points in space can be used by a spacecraft to reduce the fuel consumption needed to remain in position. L2 is ideal for astronomy because a spacecraft is close enough to readily communicate with Earth, can keep Sun, Earth, and Moon behind the spacecraft for solar power, and (with appropriate shielding) provides a clear view of deep space for our telescopes. UL SPACE CLUB

STELLAR CHRONICLE 19 . Figure 2: JWST Primary Mirror EDU coated in gold and JWST Flight Tertiary Mirror Mission: The James Webb Space Telescope will be a giant leap forward in our quest to understand the Universe and our origins. Webb will examine every phase of cosmic history: from the first luminous glows after the Big Bang to the formation of galaxies, stars, and planets to the evolution of our own solar system. Webb’s infrared vision will allow it to peer back more than 13.5 billion years, toward distant stars and galaxies whose light has been stretched to infrared wavelengths by the expansion of the Universe. It will also be able to penetrate dust-swathed regions such as the places where stars are born and to probe the atmospheres of planets beyond the Solar System. It is designed to answer outstanding questions in all fields of astrophysics. If everything goes as planned over the next six months, mission scientists will be under intense pressure to release stunning images and data from Webb as soon as possible. A small committee of astronomers at the Space Telescope Science Institute in Baltimore, Maryland, which operates Webb, has drawn up a secret list of which objects to observe first. The first tranche of results will probably include spectacular images of and data on planets, stars, and galaxies, to show off the telescope’s capabilities. After that, science will begin in earnest for the other astronomers who are queuing up to use Webb. The following are the major scientific breakthroughs expected from JWST Infra-Red Telescope Observations !!! 1. Early universe Webb will be a powerful time machine with infrared vision that will peer back over 13.5 billion years to see the first stars and galaxies forming out of the darkness of the early universe. 2. Galaxies Over Time Webb's unprecedented infrared sensitivity will help astronomers to compare the faintest, earliest galaxies to today's grand spirals and ellipticals, helping us to understand how galaxies assemble over billions of years. 3. Star Life Cycle Webb will be able to see right through and into massive clouds of dust that are opaque to visible-light observatories like Hubble, where stars and planetary systems are being born. 4. Other Worlds Webb will tell us more about the atmospheres of extrasolar planets, and perhaps even find the building blocks of life elsewhere in the universe. In addition to UL SPACE CLUB

STELLAR CHRONICLE 20 . other planetary systems, Webb will also study objects within our own Solar System. First Results: The James Webb Space Telescope's main mirror is fully aligned and performing even better than it had been designed to do, NASA officials revealed in a news conference held virtually on Wednesday (March 16).An image taken by the James Webb Space Telescope during its alignment process shows galaxies and stars in the background. (Image credit: NASA/STScI). James Webb Space Telescope already discovered many million Light Year Old Galaxies in Space. With all its gear deployed, aligned, and cooled down, Webb will be able to see the first stars that sprung up in the nascent universe only a few hundred million years after the Big Bang. Figure 2: JWST Primary Mirror EDU coated in gold and JWST Flight Tertiary Mirror Most recent Stunning Pictures: Recently, on 10th May, James Webb Telescope has once again wowed astronomers as it captures a part of the sky in unprecedented detail that was never seen before. UL SPACE CLUB

STELLAR CHRONICLE 21 . Figure 2: JWST Primary Mirror EDU coated in gold and JWST Flight Tertiary Mirror The latest image shows interstellar gas in unprecedented detail, which was previously missing in the Spitzer image. “You can see the emission from polycyclic aromatic hydrocarbons or molecules of carbon and hydrogen that play an important role in the thermal balance and chemistry of interstellar gas,” NASA added. References: [1]https://www.nature.com/articles/d41586-021-03655-4?WT.ec_id=NATURE- 20220107 [2]. https://www.space.com/james-webb-space-telescope-why-distant-orbit-l2 [3]. https://spacenews.com/nasa-completes-major-jwst-deployments/ [4].https://www.space.com/james-webb-space-telescope-better-than-expected-i mage [5].https://www.discovermagazine.com/the-sciences/how-the-james-webb-space -telescope-will-peer-back-in-time UL SPACE CLUB

STELLAR CHRONICLE 22 . [6] https://www.space.com/news/live/james-webb-space-telescope-updates Useful Video Links: [1] https://www.youtube.com/watch?v=7PHvDj4TDfM [2] https://youtu.be/RzGLKQ7_KZQ [3] https://m.youtube.com/watch?v=fZgc0jeFEpQ [4] https://www.youtube.com/watch?v=WNiVlqQ9U5c [5] https://www.youtube.com/watch?v=3QdcoMyF-Xg UL SPACE CLUB

STELLAR CHRONICLE 23 . Black Holes: A Bizarre Myth Arya Sudhakaran, Co-ordinator, UL Space Club For the last decade or so, Astronomy and Astrophysics have been changing at a very fast pace. As a space enthusiast, I’m always curious about the truths, myths, and mysteries of space phenomena. It’s always fun to watch the night sky! Because not everyone can peer into the darkest skies and resolve the mysteries surrounding them. Our universe is filled with so weird and wonderful things…. Perhaps one of the weirdest ones is Black Hole. An object that everyone has heard about, but not many understand- a Black Hole. Moreover, something about Black Holes is always bizarre! That helped me to look deep into the mysteries surrounding the mysterious black holes. Though full details on Black-Hole mechanics are not yet fully discovered, researchers have ruled out some of the most popular myths. The theory of Black holes started black in the 1900s. Albert Einstein was the person to predict the existence of Black Holes through his General theory of relativity. The term Black holes were coined by John A Wheeler in 1967, 12 years after the death of Einstein. Black Holes are not a fictional science, it is something beyond that. Isaac Newton introduced the Universal Law of Gravitation, which gave the theory that gravity always acts downward. If a ball is thrown up, it comes down, because the earth’s gravity is at work. If something is thrown up and if it doesn’t return, the velocity with which it is thrown is called Escape velocity. Black Holes are supermassive objects, their mass is so much bigger, that even the light with a velocity of 300000000 cannot pass through them. Such objects will have a zero radius. Just like nothing can travel faster than light, anything that enters or gets too close to black holes essentially becomes a part of black holes and gets added to its mass. If any light enters the black hole, it can never escape and hence black holes are black!. But is it possible for the sun to become a black UL SPACE CLUB

STELLAR CHRONICLE 24 . hole? No, it's not possible due to its low mass. But then assume, if such a situation is possible then the whole mass of the sun needs to be packed within a few kilometres of diameter close to 3 km. That is mathematically anybody can be a part of the black hole, even the sun, earth, moon, building, or even us humans. For that mass needs to be compressed down to a very small radius called Schwarzschild radius. When Einstein proposed the general theory of Relativity, He proposed the connection between spacetime, A mathematical model that describes the connection between three-dimensional space and one-dimensional time in a single four-dimensional manifold. According to Einstein, space and time are lying in a framework where space-time tells where an object should move and the object moves and the object distorts the space accordingly. This was a geometrical problem in Einstein’s presentation. Though it was a difficult mathematical problem, Karl Schwarzschild solved it. In Schwarzschild's solution, he describes space-time under the influence of a massive, non-rotating, spherically symmetric object. And Schwarzschild's solution to the General theory of UL SPACE CLUB

STELLAR CHRONICLE 25 . relativity showed that there are inhabitable conditions where there can be objects from which light cannot escape. The radius of such objects is called the Schwarzschild radius. Mathematically for the earth to become a black hole everything needs to be compressed down to a very small size, approximately the size of a golf ball! Just like the earth orbit the sun, Sun also orbits the Milky way, in which the center of it has the presence of a supermassive black hole called Sagittarius A*. It is about four million times more massive than the Sun. Then how come the sun doesn't fall to such a great pit? It’s because the sun is almost 26000 light-years away from it. For an object to fall into a black hole, it should come close to the event horizon, a point of no return. It is a boundary that separates events inside the black holes from the other parts of the universe. Once we cross the event horizon, we need to travel faster than the speed of light to escape from the black hole, funnily this is even impossible for light and thus event horizon is called the point of no return. Mysteries to this black hole story came to an end when scientists unveiled the first-ever picture of black holes in April 2019.The Event Horizon Telescope has obtained the first-ever image of supermassive black holes and their shadow. The image below reveals the central black hole of Messier 87, a massive galaxy in the Virgo cluster. For decades, scientists have been aware of the dark heart at the center of our Milky Way galaxy, known as Sagittarius A* (Sgr A*). UL SPACE CLUB

STELLAR CHRONICLE 26 . For the first time, we now received the image of Sgr A* in May 2022. It is the second black hole to be imaged by the Event Horizon Telescope. Imaging Black holes is not an easy task. Black Holes are completely dark and supermassive, hence taking a direct image is nearly impossible. To solve this problem and to take an image, EHT combines several radio telescopes located around the world to form a huge one. And thus, the imaging was obtained with the help of this huge EHT and with the help of many scientists.Is there any relation between time travel and black holes? In 1905, Albert Einstein gave a theory of General relativity. Until then it was thought that time ticks the same pace for all, and it was absolute. But time is relative. Time doesn't tick at the same pace for everyone in this universe. A general rule is that the greater the gravitational field, the slower the time ticks for you. On earth, this doesn't make a difference because these effects are negligible. When we leave earth and travel to black holes, time stops ticking at all. Einstein's thought experiments took diverse forms. One such famous thought experiment is called the twin paradox. Assume the twins ‘A’ and ‘B’ decided to orbit a black hole for five years, While ‘A’ stayed here on earth and decided to wait for ‘B’. Five years passed. They were both 20 years old when ‘A’ left for black holes, 5, 10, 25, and 50 years passed, and it’s when ‘A’ returned. I.e, ‘A’ is now 25 years old, while ‘B’ is almost 70 UL SPACE CLUB

STELLAR CHRONICLE 27 . years old. According to this paradox, ‘B’ travelled 50 years into the future in just 5 years of life. Though it might sound like science fiction, it is something so real. Source: EH Telescope When we look at the equations of the general theory of relativity in a new light, the laws of physics do not forbid time travel. Our world, our earth, our universe, all these are a small spec of the universe that is out there. As science is progressing day by day, many strange myths are opening day by day, there are answers for many such stories and there are still questions unable to answer. As such new changes happen, our structural world views are changing in a good way to evolve our ideas of the universe. But, even now Black Holes are still a bizarre dream…. UL SPACE CLUB

STELLAR CHRONICLE 28 . Ellipses to the Infinity Abhiram T P, Student Member, UL Space Club Did you ever imagine that you are going to space wearing heavy space suits and flying weightless in space? Yes, all people will dream to be an astronaut. But, have you ever thought about the challenges in space and the complications of space travel? Not only for human space flights but also satellites. Space is like an endless beautiful canvas including so many dangers like the mind-blowing gardens made by witches. Space consists of so many beautiful things like stars, supernovae, black holes, etc. These all are that much beautiful to human eyes and also provide infinite resources to humanity to possess the whole universe in our hands. But, in reality, space is very dangerous with so many dark powers. Some of you may have heard that space will never tolerate even 0.000000001% of wrong calculations. So, it is very hard to design a mission to touch space. Sometimes this feature of science will appear in the air also. But in the air, it is quite simple to solve the solvable problems. The designing of the orbits is also a very important part of the designing process of space missions. To understand the orbit design, we must understand the orbits and their specialties. These orbits are not made by space, these are imaginary ellipses made by the great humanity to simplify our missions to space. An orbit is a typical, repeating path, in which an object takes another object. The objects moving through this path are simply called satellites. These things can be natural or man-made. For example, the Moon, Mars, Earth, comets, man-made satellites like GSAT,INSAT, Chandrayaan orbiter, MOM, ISS etc. Even our Sun is also moving through an orbit. The planets, comets, and meteors in the solar system are orbiting around the Sun through an imaginary flat surface, this surface is called the ecliptic plane. What is the shape of an orbit? Do all orbits possess the same shape? Are all orbits in a circle? Or in an ellipse or the shape of an egg? In reality, all orbits are elliptical (similar to an oval). In the case of planets, the majority have an elliptical orbit to orbit around their parent planet, star, or anything like that. But, comets are entirely different. They are having UL SPACE CLUB

STELLAR CHRONICLE 29 . highly eccentric elliptical orbits than planets. They have a relatively very distant aphelion and a very low range of perihelion. The celestial bodies which are orbiting their parent bodies are not always having the same distance from the parent bodies. In the case of satellites orbiting Earth, the nearest point is called perigee and the farthest point is called apogee. For the planets orbiting the Sun, they have the farthest point aphelion and closest point perihelion. We reach our aphelion during the summer in the northern hemisphere. And the time that a planet takes to orbit the Sun is called the time period. For Earth, we have a time period of 1 year. In the case of geostationary satellites, they have a time period of ≈ 24 hours ≈ 1 day. Why is a satellite not thrown away from an orbit? As we studied in lower classes, Newton’s first law states that an object in motion will stay in motion unless an external force is applied to it. If Earth doesn’t have gravity, our satellites will go into deep space in a straight line. A constant tug of war which is powered by the tendency to move in a straight line and gravity, which is pulling the satellite to Earth is happening between the satellite and Earth. To make a good orbit we need the chemistry between momentum(m×v) and force of gravity. Both of them must be balanced. As a reader of this magazine, you might be a science aspirant, so, you must question all the answers to science. Then, what if any one of these forces will overtake the other one? If the momentum of the satellite increases too much, then, the satellite will be fired into deep space without any navigational controls. If the momentum will decrease less than the force of gravitation, it will never be able to touch the orbit and crash down and it will fall to the Earth. When the force and momentum are balanced, the satellite will continue in free fall and it will never hit the planet. This special velocity to form or to continue in an orbit is called orbital velocity. UL SPACE CLUB

STELLAR CHRONICLE 30 . The satellites in higher orbits have lesser orbital velocity and the satellites in lower orbits have greater orbital velocity. Different types of orbits As we know, there are so many types of orbits for our Earth-orbiting satellites. You may hear about the orbits like GEO, LEO, MEO, etc. Except this, there are so many other types of orbits that are designed for different purposes. UL SPACE CLUB

STELLAR CHRONICLE 31 . Geostationary Orbit (GEO): Satellites in GEO orbit parallel above the equator from west to east taking 23 hrs, 56 mins, 4 sec which is ≈ 1 day. In this orbit, satellites are orbiting at exactly the same rate as Earth. This makes satellites in this orbit stationary over a fixed location with an altitude of 35786 km and a velocity of 3 km/s. GEO is used by so many satellites that need to stay fixed above one particular area on Earth, such as telecommunication satellites. This way, an antenna on Earth can be fixed to always stay pointed towards these satellites without changing its direction or position. It can also be used by weather monitoring satellites because they want to observe an area to predict the upcoming changes in weather in that region. Orbits like GEO will help us to observe a wide range of places on Earth, about 1 /3 of the total surface of Earth. IRNSS, GSAT, INSAT series satellites of ISRO, and GOES of NASA are examples of Geostationary satellites. Low Earth Orbit (LEO): As its name indicates, low earth is an orbit, which is relatively closer to earth as well as small. Its altitude varies from 160 km- 1000 km. 160 km is smaller than others, but still, it is very far as the maximum altitude of a fighter jet is ≈ 20 km. The altitude of LEO is 8 times farther than it. Unlike geostationary satellites, a satellite in LEO doesn’t need to orbit along the equator or some specified area, its orbital plane can be tilted. So, like bikes on our roads, satellites in LEO have more routes to do their duty. This is one of the main reasons behind the wide usage of LEO satellites. LEO’s relatively close distance to Earth allows the satellites to make the most accurate results. That’s why this orbit is commonly used for satellite imaging due to its UL SPACE CLUB

STELLAR CHRONICLE 32 . capability to take images with very high resolution. Our ISS(International Space Station) is also placed in this orbit, as it is easier for astronauts to travel to and from it at a shorter altitude. The satellites in this orbit will take almost 90 minutes with a speed of 7.8 km/s. This means these satellites will circle Earth 14 – 16 times in a day. This orbit is generally not used for the telecommunication satellites. Because it will be very hard for these fast-moving satellites to track ground station signals. Instead of telecommunication satellites, this orbit mainly consists of some satellites in a series or in a combination which is used to provide increased coverage. These satellites are creating a net above the Earth and the satellites in a series are working together and creating teamwork to provide good service. EOS-01 and RISAT-2B of ISRO and R3D2 of DARPA(Defence Advanced Research Projects Agency) are the major examples of the satellites in LEO. And also, as we know, the ISS is located in LEO. Medium Earth Orbit(MEO): Medium Earth Orbit consists of a wide distance between LEO and GEO. Like LEO, the satellites in MEO also don't need to orbit above a specified path. And it is used for various applications. This orbit is very commonly used by navigation satellites. It is lying between 2,000 km and 35,786 km. Satellites in LEO have a period of fewer than 24 hrs and more than 2 hrs. MEO includes famous Van Allen radiation belts which can damage any type of satellite which doesn’t equip with special shielding. The semi-synchronous orbit which has an altitude of 20,200 km is a special orbit, which allows the satellites to pass over a region 2 times a day. This semi-synchronous orbit is used by GPS(Global Positioning System) of the UL SPACE CLUB

STELLAR CHRONICLE 33 . USA.If you heard about MEO, you might hear about Molniya orbit. It is an orbit that is placed in the region of MEO with high inclination(63.4°) and high eccentricity(0.722). This orbit has 12 hours of the period. Satellites in this orbit spend their most orbit above the chosen area in high latitudes. This name is derived from Russian Molniya military communication satellites. GPS of NASA, GLONASS of ROSCOSMOS, NAVIC of ISRO, BEIDOU of CNSA, and GALILEO of ESA are the main examples of MEO satellites Polar Orbit and Sun-Synchronous Orbit(SSO): Satellites in polar orbit are designed to pass over the poles of Earth. The Polar Orbit satellites do not have to pass exactly over the poles. If a satellite with a deviation from 20-30 degrees is even considered as a polar orbit satellite. This orbit is also a part of LEO with an altitude of 200-1000 km. Sun-Synchronous orbit is a type of polar orbit. The satellite SSO will always synchronise with the sun. That simply means they will always be in a fixed position related to the sun. This means an SSO satellite every day visits the same place at the same local time. For example, if an SSO satellite named ‘X’ is passing through Dehradun at morning 9 O'clock, on all days, it will pass over Dehradun at 9 O’clock which is based on the local time. UL SPACE CLUB

STELLAR CHRONICLE 34 . This specialty of this orbit will help us to monitor the changes of a place in different seasons. And also, this orbit is used to monitor floods, forest fires, deforestation, etc. The altitude of SSO is between 600-800 km. The speed of a satellite in SSO is between 6-8 km/s. CARTOSAT-2 of ISRO and AEOLUS of ESA are the main examples of satellites in SSO. Transfer Orbits and Geostationary Transfer Orbit (GTO): As their name indicates, transfer orbits are the orbits that are used by satellites to get one orbit to another one. If we launch a satellite in our rockets, directly the satellites may not be placed in the target orbit. With the usage of a very small amount of fuel, the satellites or spacecraft can move from one orbit to another orbit by using in-built motors. In short words, it allows the spacecraft to reach their decided orbit without giving more effort. This is a shortcut. Transfer orbit to GEO is simply called Geostationary Transfer Orbit(GTO). The orbits with low eccentricity will make the orbits in round shape, which will keep the distance with Earth almost equal. But, a highly eccentric orbit will build an ellipse orbit. On an extremely eccentric orbit like this, the satellite can rapidly go from being very distant to very close to Earth’s surface depending on where the satellite is on the orbit. In transfer orbits, the payload uses engines to go from an orbit of one eccentricity to another, which puts it on a path to higher or lower orbits. Lagrange Points For the satellites near the Earth such as telescopes and other observatories in space, they will face so many issues while taking the pictures of deep and dark space due to the deflection of sun-rays which is consisting of so many UL SPACE CLUB

STELLAR CHRONICLE 35 . radiations like IR(Infra-Red) and visible light. It will prevent the telescope from taking the images of so many galaxies or other celestial bodies like black holes and supernovae. So, taking deep space images near this glowing Earth will be a Thuglak attempt. Lagrange points (L-points) allow for orbits that are much farther away (over a million kilometres) and do not orbit Earth directly. These specific points are far from the Earth as well as the Sun where their gravitational fields combine. These points will allow satellites to orbit stable and the spacecraft will be anchored to the mother Earth. If we launch a spacecraft far beyond Earth’s gravitational field, it will start to orbit around the Sun, if it is not directed to any other planets. These satellites may feel communication difficulties. But, if we fix the spacecraft in L-points, it will be easy to communicate and our objectives will also be fulfilled. The most used Lagrange points are L1 and L2. These points are about 1.5 million kilometres away from Earth, but it is only a 1% of AU(Astronomical Unit- Distance between Sun and Earth). The upcoming JWST (James Webb Space Telescope) of NASA and ISRO’s future mission ADITYA-L1 – Both are planned to be in L-points. PLANCK was also launched to L-point. ADITYA-L1 will be in First Lagrange Point (L1) and JWST will be in Second Lagrange Point (L2). Raising up our technology This is not a full knowledge about a very panoramic branch of science and technology. As we know, humans are a special creation of God. A complicated machine that can think, smile, read etc. We humans are also famous for our creations. We created so many things with the help of our mother nature. We have the quest to explore the unknown, that was, is and will be the fuel to raise our power. Power is not always about conquering something, it is also about to know about something. We are not at the peak of development of science and technology. We are still developing our knowledge to survive, to not extinct from Earth, we will surely continue it. We need to power it up for the future. UL SPACE CLUB

STELLAR CHRONICLE 36 . And the Journey Still Continues.. Krishnendu, UL Space Club Member The reddish soil, dusty wind..it all are the attractions of the Mars and now we colonised it said Martinho,who are going to mars on the next Sunday as a part of the Mission Mangal'.He is all set to go to Mars with his elder sister and parents.All of them are super excited and well trained.During these training days all of them except Martinho was dreaming about their journey but Martinho was thinking about Mars and the earth.He is an aspiring scientist.He always questions everything with his own friend 'why?' Mummy, why are we going to Mars? Martinho asked his mother.She replied to explore my son. We are always curious to know what is out there. So to know Mars we are going to Mars. mummy I love our earth so when we go to Mars I will definitely miss our earth he said.'Nothing is stable.Everything will change so we should change accordingly a change is necessary we will come back to earth after some years you don't worry' his mother replied.mummy now I remembered the pictures which you showed me. Those pictures of the earth was really beautiful then how the Earth changed to the the earth we see today.she didn't said anything for a few moments.Suddenly she became sad.By seeing his speechless mummy Martinho asked once again.mummy said I will tell you later.mummy I really wish to see that beautiful Earth martinho's mother bowed head because of guilty.Her generation is the reason for the current situation of the earth.The biggest mistake ever done. Mummy, did you pack the food items for our trip to Mars? Take some seeds too.I want to plant trees in Mars.mummy replied Martinhothere are some nutrients needed for plant growth in martian soil but not in the exact amount.So we should take some fertilisers too. But now it is not possible. Martinho's smile faded. Don't worry son.We can take it next time.Suddenly some thoughts came into her mind as a cyclone. Children in this generation are willing to plant trees and conserve the earth.Then why didn't people of my generation including me think like that?That is a big mistake.but now we have find the solution to survive.The thoughts about their Mars journey blowed through her mind by giving a cool feel. Days passed and here comes the day for the launch. They all are excited for the journey. The countdown begins 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0. The rocket lifted off and the curious journey of humans still continued for a bright future. UL SPACE CLUB

STELLAR CHRONICLE 37 . Exoplanets and the Possibility of Life Beyond the Earth Vismaya M.P , Abhiram V.R, Rithin S.B. & Swetha C The discovery of solar eclipses has been a milestone in the history of astronomy. We now live in a universe of exoplanets. The number of certified planets is in the thousands and is increasing almost every day. The number could rise to tens of thousands within a decade, as we increase the number, and viewing power of robotic telescopes mounted in space. With an incredible number of people working on this field , the advancement that this field is going to witness is unpredictable. Astronomers have already discovered a number of potentially habitable exoplanets and some have already considered the possibility of creating a life there. Even though studies are going on about exoplanets and the possibility of existence of life out there, apart from the people working on this field, the public remain unaware about this possibility and also the risks coming along with it. These pros and cons of establishing a life beyond our earth are discussed further. 1. Introduction: 1.1 Formation and Evolution of Exoplanets: This is a once-in-a-lifetime opportunity in human history: we are on the verge of solving problems that have plagued civilization for thousands of years for the first time: Is it possible that there are other planets that are comparable to Earth? Is it common to come across them? Is there any evidence of life? The field of exoplanets is rapidly moving toward answering these questions, with the discovery of hundreds of exoplanets now pushing toward lower and lower masses; the Kepler Space Telescope’s yield of small planets; plans to use the James Webb Space Telescope (launch date 2014) to study the atmospheres of a subset of super Earths; and ongoing development for technology to directly image true Earth analogues. The basis for prediction and interpretation is UL SPACE CLUB

STELLAR CHRONICLE 38 . provided by theoretical research in dynamics, planet formation, and physical features. People outside the field of exoplanets frequently wonder if the field is similar to the dot.com bubble, which would burst, dampening excitement and development. Exciting discoveries and theoretical advancements, in my opinion, will continue endlessly in the years ahead, but at a slower rate than in the previous decade. The reason for this is that observations have found new types and populations of exoplanets recently, and these observations rely on technical advancements that take a decade or more to mature. The radial velocity approach, for example, was used to discover all but one exoplanet in the early 2000s. Many organisations around the world were working on large-scale transit surveys at the time. However, the transit approach was not used until, a decade into the twenty-first century, to account for about a quarter of all known exoplanets. Planet finding techniques such as astrometry (which has yet to detect a planet) and direct imaging have not yet matured; when they do, planets will be discovered inside a new parameter space of planet mass and orbital properties. Furthermore, researchers are aiming to increase the precision of existing planet discovery techniques in order to detect lower-mass planets and those that are farther from the star. Overall, technology allows for modest but steady advancement, which fosters continual discovery. Theories, like observations, require time to develop and emerge. A “ultimate” planet formation model, akin to the “millennium simulation” for galaxy creation and evolution, is expected. Incorporating comprehensive physics and being able to duplicate the generic outcome of planet populations (mass, radius, and orbital properties, including period) would allow for a better understanding of planet creation and migration in the future. A three-dimensional Monte Carlo code that includes radiative transfer with inhomogeneous cloud coverage and surface features, as well as a code that solves for the temperature structure and combines with a hydrodynamical simulation to calculate the three-dimensional temperature and wind structure, could be the ideal exoplanet atmosphere code of the future. Classical orbital mechanics, which has already been re-energized by intriguing exoplanet systems (e.g., planets in resonant orbits, hot Jupiter exoplanets that orbit in the opposite direction of the stellar rotation), can also be used to explain fundamental mechanisms of how planetary system configurations came to be. The basis for prediction and interpretation is provided by theoretical research in dynamics, planet formation, and physical features. People outside the field of exoplanets frequently wonder if the field is similar to the dot.com bubble, which would burst, dampening excitement and development. Exciting discoveries and UL SPACE CLUB

STELLAR CHRONICLE 39 . theoretical advancements, in my opinion, will continue endlessly in the years ahead, but at a slower rate than in the previous decade. The reason for this is that observations find new types and populations of exoplanets, and these observations rely on technical advancements that take a decade or more to mature. Because of their perturbations on transiting planet signals, orbital dynamics modelling is driving the search for moons and other undiscovered planet partners. Exoplanets is a unique study in that it encompasses a wide range of fields both inside and outside of planetary science and astronomy. Geophysics, high-pressure mineral physics, quantum mechanics, chemistry, and even microbiology are among the other disciplines. While exoplanet sightings plainly belong in the field of astronomy, the entire field of exoplanets has been without a home for many years. 1.2 History of detection of exoplanets: Scientists discovered the first exoplanet, or planet outside was our solar system, in 1992. It was, however, not in the condition they had hoped for. Neutron stars are the densest things in the universe, aside from black holes. They form when a giant star dies and its core collapses, causing it to explode outward. Simply said, the star expands to the point where it can no longer sustain itself and expels all of its energy into space. The core functions as a sort of explosion trigger. Depending on its size, the star becomes a neutron star or a black hole when its core collapses. Pulsars are neutron stars that release radio-frequency \"pulses\" on a regular basis. Many of them can be compared to drummers, as they have rapid and regular rhythms. Those pulses are so regular that astronomers can tell if something is wrong if they don't come at the appropriate intervals. In 1992, a breakthrough offered irrefutable proof of the existence of planets. The pulsar PSR B1257+12, 2300 light-years distant, was detected by astronomers Aleksander Wolszczan and Dale Frail. It should have pulsed every 0.006219 seconds, but it's pulses were a touch wrong now and again.Those off-beats, on the other hand, came at regular intervals. Wolszczan and Frail came up with an explanation after a lot of research: it had two planets around it. The mass of one was three times that of Earth, and they rotated every 67 and 98 days, respectively. Pulsar planets are a cross between a chimaera and a zombie. When a star explodes, the planets in its system are usually killed or thrown away by a shockwave. However, once the violence has subsided, the gas and dust might condense again. This implies that the three planets in B1257 could be formed up of remnants of planets that came before them.Given the severe radiation levels in these systems, nearly no one has ever considered the B1257 system as a UL SPACE CLUB

STELLAR CHRONICLE 40 . possible home for life. While the discovery of planets orbiting another star in 1992 was significant, it left astronomers with no proof of planets around a main sequence star like the Sun. That kind of validation would have to wait a few years. 1.3 The foundation for exoplanets: Many groups have been searching for the first planet around a Sun-like star since the 1980s. There were some candidates who came and went. Others necessitated dozens or hundreds of observations before they could be officially confirmed. However, an observation made in January 1995 proved to be accurate. Didier Queloz, a graduate student at the University of Geneva, was working on the hunt for extrasolar planets using radial velocity, or wobbles, with his professor, Michel Mayor. His discovery was said to be a happy accident. He chose 51 Pegasi, an F-type star around 50 light-years away, from a library of radial velocity signatures. He was attempting to calibrate his planet-finding code, and the star was one of a few viable options. Everything came together that night, with a strong signal every four days or so .The object's minimum mass was found to be near Jupiter, indicating that it was unmistakably a planet. While astronomers believed such periods were possible, they weren't necessarily expected to be discovered in such a short time. In 2016, Queloz told the BBC, \"At this time, I was the only one in the world who realised I had discovered a planet.\" \"I was terrified, to tell you the truth.\" There was cause to be concerned: discovering a planet was — and still in some ways — difficult, and there were numerous errors, ghosts, odd data points, and other hitches that never seemed to result in the formation of a planet or a brown dwarf. Despite this, Queloz's data indicated that the half-Jupiter-mass, fast-moving, ultra-hot planet was present. Queloz spent the rest of 1995 trying to persuade Mayor that he had indeed discovered a signal, rather than an instrument malfunction or other observing anomaly. In October 1995, their study was ultimately published. Following up on the observations, astronomer Geoff Marcy discovered that the Geneva team was correct — he and collaborator Paul Butler were able to find the same signature at a different observatory.Taking things one at a time vs. all at once. Exoplanet detections in the early days were defined by an emphasis on star-by-star investigations, nearly invariably via radial velocity, making radial velocity one of the most effective methods for finding exoplanets, with 746 worlds discovered as of March 2018. Compare that to 90 planets discovered through direct imaging (which is confined to huge, hot, and young planets) and 67 planets discovered through microlensing, which occurs when a large object UL SPACE CLUB

STELLAR CHRONICLE 41 . passes in front of a background star and acts as a gigantic magnifying glass. Those are the third and fourth most effective ways for discovering exoplanets, respectively.The transit method of detecting exoplanets, on the other hand, has proven to be the most successful. Within the same timeframe as the radial velocity headcount, it was discovered 2,789 times. Because there are 3,705 planets in the universe, transiting planets account for 75% of all identified planets. One spacecraft, Kepler, has discovered approximately 2,648 of the 2,789 planets. We have only 1,000 planets to work with if you exclude the worlds identified by NASA's Kepler spacecraft. That's because Kepler was designed to survey a single small piece of sky and count as many planet transits as possible.Previous polls only included a few hundred stars at a time, if that. If nothing else, Kepler demonstrated that planets aren't uncommon, and that there are millions — if not trillions — out there waiting to be discovered. For example, researchers operating under a strong cloak of secrecy claimed in 2016 that they had discovered the closest planetary system to Earth orbiting around the star Proxima Centauri. That team, formerly known as Pale Red Dot, later changed its name to Red Dots. Their research has expanded to include other neighbouring systems, including as Barnard's Star, where they discovered tantalising evidence of an exoplanet in November 2018.Sara Seager, MIT's resident planetary expert, remarked in a 2018 conference lecture that exoplanet astronomy is returning to its roots in some ways. There will still be some large-scale surveys, but they will be used to identify a small number of potential candidates for future research. Other projects, such as Red Dots, will concentrate on a select celebrity at a time. This is partially because, thanks to much of the heavy labour done on star censuses, we are on the verge of learning previously unimaginable data about planets - and we may be studying them one by one with massive telescopes and improved optics. 2. Methods of detection of exoplanets The detection and understanding of exoplanets can lead us to one of the most historic discoveries ever - the possibility of life beyond earth. But the detection of exoplanets is a rather difficult task because their parent stars are much brighter and more massive than planets, and most stars are so far away that the planets are lost in the glare. It is this brightness of the parent stars that makes exoplanets so hard to find. Over the years, astronomers have developed a number of methods for the detection of exoplanets. There are both direct and indirect methods in practice. All of them rely on detecting a planet's effect on its parent star, to infer the planet's existence. UL SPACE CLUB

STELLAR CHRONICLE 42 . Direct detection Techniques: 1. Direct imaging method And indirect Techniques: 1. Radial velocity 2. Astrometry 3. Pulsar timing 4. Transit Method 5. Gravitational microlensing 6. 2.1 Imaging Since the star is brighter than the planet, this is the most difficult method of detecting an exoplanet. The only way to expose a planet is to decrease the brightness so that it can be seen,observed in the star's shadow. This is accomplished in two ways. a) Coronagraphy: In this procedure, a gadget is attached to the telescope and used to see the stars before the starlight reaches the telescope's detector, it is blocked. The bright central core of the star is obscured by a coronograph, leaving only the faint outline of the star. The corona is the outer plasma area of a star's atmosphere that may be seen. As a result, any close planets will be seen. b) Starshade: The starshade (also called an external occulter) is a spacecraft that will enable telescopes in space to take pictures of planets orbiting faraway stars. It is designed to fly in front of a telescope and block the immense glare from a star’s light before it enters the telescope, allowing the planet’s reflected light to pass through and be collected. To successfully achieve starlight blocking, the starshade must unfurl and expand in space to almost the size of a baseball diamond (34 m diameter). The starshade’s razor-sharp petals redirect the effects of diffraction—the bending of starlight around the petal edges producing unwanted glare—and create a dark shadow for the trailing telescope to fly in. UL SPACE CLUB

STELLAR CHRONICLE 43 . 2.2 Radial Velocity method The radial velocity method, often known as the stellar wobble method, entails detecting the Doppler shift. Observing the light from a specific star to check if it oscillates on a regular basis colour shifts between red and blue. The planet and the star are both in orbit around each other. They have a single centre of mass and exert their own gravitational pull. As a result of this gravitational force,both encounter a gravitational interaction. Since the star will be huge and large, it will have a strong gravitational field. The planet, on the other hand, is small and has less gravity. However, it has an influence on the gravitational field of a star, even if it is not as strong as the effect of a star on a planet. The planet's gravity causes the star to wobble somewhat. The star's swaying tells us something about the situation. The quantity and size of planets, as well as their presence.The Doppler shift can be used to detect the star's wobbling. The visible light from the planet bunches up and appears more in blue as it approaches closer to the observational point (or telescope) (blueshift). Whereas when the planet moves away from the observation point (or telescope), it is said to be moving away. The visible light from the planet has expanded out, making it appear more red (redshift). Observation of the spectrum's periodic change of colour indicates that there is a planet around the star. UL SPACE CLUB

STELLAR CHRONICLE 44 . 2.3 Astrometry The astrometry approach is utilised to find out what's going on in the sky, measuring the slight regular perturbation in the position of a star to find exoplanets. As a result of its invisible companion in the sky, the star moves in a short circular orbit, with a radius determined by the planet's mass and distance from the star. Changes in the apparent position of the star can also be used to study the star's wobble. The detection of exoplanets using astrometry is also difficult,because the star wobbles at such a small distance that it's difficult to discern planet wobble, particularly from minor planets.Taking a series of photographs of a star and some neighbouring stars can thus be used to trace the movement of these stars. The distances between these reference stars are compared in these photos. The wobbling star has also been noticed. If the target star has shifted, by analysing its movement in relation to other stars, the presence of an exoplanet can be analysed. This method requires precise optics because our atmosphere bends and distorts light. 2.4 Transit Method: When a planet passes directly between star and observer, it dims the star's light by a measurable amount. The transit method measures the drop in brightness when a planet transits in front of the star (as seen from Earth). With this method we can only find a minor fraction of the existing exoplanets and its UL SPACE CLUB

STELLAR CHRONICLE 45 . star has to be perfectly aligned in order to observe an exoplanet's transit. In a graphical representation a dip will be observed when the planet passes to the star. If there are multiple planets then multiple dips according to their size and passing time will be observed. The small size planet will produce a tiny dip and a large planet will give a long dip. 2.5 Pulsar Timing: The presence of a planet orbiting a star affects the timing of the regular signals emitted by the star itself. This phenomenon can be used to detect planets around a pulsar. Pulsars emit radio waves regularly as they rotate, creating a periodically pulsed beam, like a lighthouse. If an orbiting planet perturbs the motion of the star, then the timing of the beam is also affected, and this is how the first exoplanets were detected. The orbit as well as the mass of these planets can be observed by precisely measuring irregularities in the timing of the pulsars. 2.6 Gravitational Microlensing: The gravitational pull of a large object will bend the light from distant objects and amplify it, acting like a magnifying lens. Light from a distant star is bent and focused by gravity as a planet passes between the star and earth i.e. when light from the background object travels towards Earth, it's path is bent or warped as it bypasses any large foreground object that is aligned with the background light source. As the microlensing effect works on radiation from the UL SPACE CLUB

STELLAR CHRONICLE 46 . background source, this technique can be used to study intervening objects that emit little or no light, such as black holes, or planets around distant stars. It happens when a star or planet’s gravity focuses the light of another more distant star, in a way that makes it temporarily seem brighter. The rays of light from the more distant star bend around the exoplanet and then the exoplanet’s star. A lensing event looks like a distant star that gets gradually brighter over the space for some time and then fades away. If a planet exists and is lensed, it gives a blip of light during the brightening and dimming process. Suppose that the aligned foreground mass to be studied is a star that is hosting a planet and then the amplified light curve from the background source will contain an additional side peak. The size and shape of the secondary peak will depend on the mass and distance of the planet from the host star .The exoplanet OGLE 2003-BLG-235/MOA 2003-BLG-53 was the first planet discovered using this technique, in 2003. The disadvantage of this technique is that the effect happens only once, as it relies on a unique chance alignment of the foreground and background stars, and so measurements must be checked using other methods. 3. Kepler’s mission Kepler’s work: For centuries the search for other planets like our Earth has been revived with great excitement and popular interest surrounding the discovery of planets orbiting other stars. There is now clear evidence of a large UL SPACE CLUB

STELLAR CHRONICLE 47 . number of three types of exoplanets; gas giants, hot-super-Earths in short-term routes, and heavy snow. The challenge now is to find the planets of the earth, especially those in the astronomical observatory where fresh water can be found on the surface of the earth. The Kepler Mission is specially designed to explore our Milky Way galaxy to discover hundreds of planets the size of our Earth and smaller planets in or near the habitat and to discover a fraction of the billions of stars in our galaxy that would contain such planets. 3.1 Kepler Science: The scientific goal of the Kepler Mission is to examine the structure and diversity of planetary systems. This is achieved by examining a large sample of stars to: ● Find the percentage of planets and planets in or near the orbits of a variety of stars. ● Determine the distribution of the size and shape of the planets. ● Estimate how many planets there are in the starry system. ● Find the orbit size and shape of the planet, the size, density and density of large planets in the short term. ● Find additional members of each planet system found using other methods. ● Discover the features of those stars that control planetary systems. The second-loss of the four-wheel-drive reactor Kepler in May 2013 ended Kepler’s four-year mission to continue monitoring more than 150,000 stars in search of passing exoplanets. Developed during the months following this failure, the K2 mission represents a new concept of spacecraft operations that allows for the continuation of scientific observations with the Kepler space telescope. K2 became fully operational in May 2014 and due to a reduction in the fuel efficiency of the telescope response control system, NASA announced its cessation on October 30, 2018. Using the transport method to detect light changes, K2’s objective includes a series of viewing “Campaigns” of fields distributed across the ecliptic plane and provides photometric accuracy approaching those of Kepler’s original equipment. Working on an ecliptic plane reduces the torque emitted from the spacecraft by solar wind pressure, reducing erosion to the point where the spacecraft attitude can be effectively controlled by a combination of thrusters and two remaining reaction wheels. So each campaign is limited by sun angle constraints for a period of about 80 days. UL SPACE CLUB

STELLAR CHRONICLE 48 . 3.2 Scientific motives: K2 is a community-run machine. All K2 objectives are proposed to the public through the Guest Observer program. The power of science encompasses a wide range of astrophysics. It is expected that K2 will: ● Provide a crop of tropical planets around the bright stars to follow transport spectroscopy to facilitate rapid development in the reflection of exoplanet atmospheres. ● Provide a crop of small planets around bright, small stars to facilitate the most accurate measurement of tracking so far in quantity, density and composition. ● Identify the locations and features of the planets inhabited by the bright M-dwarfs in the solar system. ● Find out if hot gas giants are present near younger stars, or if they are moving in smaller lanes over time with the passage of waves or other interactions. ● Find the relationship between astronomical structure, rotation and activity within star bodies between age and metal size. ● Identify the ancestors of the genus Ia supernovae from the photometric structure by ascending to the size of the eruption. ● Find and mark the leading stars between open collections and star organisations. Calculate the shape of the inner star and important star structures using asteroseismology tools. ● Provide a large, general cadence survey of AGN activity to the band to see. Participate in surveillance campaigns for multiple machines, with multiple ecliptic target bands and other space-based hardware or ground-based telescopes. Source: exoplanet exploration- NASA UL SPACE CLUB

STELLAR CHRONICLE 49 . 4. Types of Exoplanets Exoplanets have been classified into four categories by scientists: gas giant, Neptunian, super-Earth, and terrestrial. They range in size from massive gas planets like Jupiter to small rocky planets the size of Earth or Mars. They can be either boiling hot or frozen solid. They can orbit their stars so close together that a “year” only lasts a few days; they can even orbit two suns at the same time. Some exoplanets are shady characters who traverse the galaxy in perpetual darkness. Other stars, however, are orbited by sorts of exoplanets that do not exist in our solar system: hot Jupiters, super-Earths, and ocean worlds expand the exoplanet spectrum beyond the rocky planets and gas giants. Each planet type varies in interior and exterior appearance depending on composition. 4.1 Gas Giants: Planets the size of Saturn or Jupiter, our solar system’s largest planets, or much, much larger, are known as gas giants. There is significant variation within these main groups. For example, hot Jupiters were among the first planets discovered–gas giants orbiting their stars so close that their temperatures exceed millions of degrees (Fahrenheit or Celsius). These planets most likely have a small rocky core, but are mostly hydrogen and helium. Planets like Jupiter, Saturn, Uranus, and Neptune are known as gas giants. These planets, like Jupiter and Saturn in our solar system, have swirling gases atop a solid core rather than hard surfaces. Approximately 25. Gas giants make up the UL SPACE CLUB

STELLAR CHRONICLE 50 . percentage of all discovered exoplanets. In 1995, the planet 51 Peg b was discovered orbiting a Sun-like star for the first time. They are thought to form within the first 10 million years of the life of a Sun-like star…or never.The temperatures of hot Jupiters reach thousands of degrees because they orbit so close to their stars.The hottest gas giant discovered so far, KELT-9b, is hotter than most stars. Jupiter has a twin, which orbits a star that is identical to our Sun. 4.2 Neptunian planets: Neptunian planets are similar in size to our solar system’s Neptune and Uranus. They’ll probably have a variety of interior compositions, but all will have rocky cores and outer atmospheres dominated by hydrogen and helium. Mini-Neptunes, planets smaller than Neptune but larger than Earth, are also being discovered. In our solar system, there are no planets of this size or type.Thick clouds obscure the signature of the molecules in the atmosphere on Neptunian exoplanets, preventing any light from reaching them. They’re 25,000 light-years distant on an ice giant exoplanet. A warm, Neptune-sized exoplanet is emitting a massive comet-like cloud of hydrogen. Planets the size of Neptune may be more likely to originate in planetary systems’ cold outer reaches than planets of other sizes. 4.3 Super-Earth: Terrestrial planets with or without atmospheres are known as Super-Earths. They are larger than Earth but smaller than Neptune. Super-Earths are possibly rocky planets with masses bigger than our own. They are planets with masses ranging from one to ten times that of Earth. The term “super earth” refers to a planet that is larger than our own. It’s possible that it’s a better place to live than our planet. Earths with superpowersThe densities of hydrogen and helium are modest, while those with high densities are rare. The UL SPACE CLUB