Pluto- The Planet That Wasn't

Pluto: The Planet That Wasn't By Readworks.org For a long time, Pluto was the smallest planet in our solar system. That was bad enough to be the smallest. But then, Pluto was told it was not a planet at all. Poor Pluto! Scientists first discovered Pluto in 1930. To discover means to find or see something before anyone else does. When scientists discovered Pluto, they called it a planet. Pluto is small. It is smaller than the earth’s moon. And it is not even as wide as the United States. Pluto is cold. It is made of mostly rock and ice. And Pluto is far away from the sun. It is so far away that it takes almost 250 years to go around the sun. Even though Pluto is small, cold, and far away from the sun, scientists still thought it was a planet. Until 2006, people thought of Pluto as the ninth and smallest planet in the solar system. But in 2005, scientists discovered a space object that was like Pluto. It was named Eris. Eris and Pluto are about the same size. They are also both part of the Kuiper Belt. This belt is a ring of objects in space. Those objects go around the edge of the solar system. Since Pluto and Eris were so alike, scientists had to make a decision. A decision is a choice. Scientists had to decide whether Eris was the 10th planet in the solar system or not a planet at all. And if Eris was not a planet, maybe Pluto was not one either. Scientists made new rules for what was called a planet. They decided that Pluto and Eris were not planets. So the number of planets in the solar system went from nine to eight. Scientists made a new name for space objects like Pluto and Eris. They called them dwarf planets. Now, Pluto and Eris are called dwarf planets. Goodbye, Planet Pluto! But at least Pluto is not the smallest planet anymore. In fact, Pluto is one of the bigger dwarf planets! Maybe Pluto does not have it so bad after all. Source: https://www.readworks.org/article/Pluto-The-Planet-That-Wasnt/fc7bcf2c- 3069-462a-b594-27f6a74702b9#!articleTab:stepreads/stepreadsSection:d939b0aa- 188c-4ed4-be24-881c3eb43cef/