New Planets
Written by Abby Cessna
The last planet discovered in our Solar System was found 70 years ago, and it turned out that Pluto was not considered a planet after all. In 2006, astronomers discovered a large object in the Kuiper Belt, which they named Eris. At first, astronomers thought that Eris was a planet because it was larger than Pluto is and orbited the Sun. It turns out that Eris was going to cause quite a stir.
In the summer of 2006, the International Astronomical Union (IAU) met to discuss Pluto's fate and the existence of Eris. Their decision was extremely controversial to say the least. The IAU created a new set of criteria for what constituted a planet, and Pluto did not meet the new standards. The new IAU definition of a planet is an object that orbits the sun, has enough mass to maintain a nearly round shape, and has enough gravity to clear any objects of comparable size out of its orbit. The IAU also created the new category of "dwarf planet," which fulfills the first two criteria of what constitutes a planet. Pluto was renamed as a dwarf planet, and Eris was also put into this category.
Astronomers have also discovered a number of extrasolar planets – planets outside of our Solar System – using mostly indirect methods, such as radial velocity, which involves calculating the movement of an object. Although astronomers have searched for extrasolar planets for over 100 years, they did not find any until 1995. To date, 353 extrasolar planets have been discovered.
There are a wide variety of extrasolar planets, which are also known as exoplanets. Most orbit stars that are similar to our Sun. This is in part because scientists have focused on these stars in the hope of finding planets similar to Earth and capable of supporting life. Despite this inclination to favor Sun-like stars, astronomers have determined that stars with a lower mass, such as red dwarfs, are either not as likely to have planets or to have too low of a mass for astronomers to detect. Because extrasolar planets are so far away, scientists have not been able to discover that much about them. Fortunately, we have learned some things. Many of the extrasolar planets are gas giants like Jupiter and are highly unlikely to support life. In the past few years, scientists found planets the size of Neptune, which strengthtened their hope for finding Earth-like planets, and some astronomers now believe they have found Earth-like planets. Astronomers think that there are many Earth-like extrasolar planets in various solar systems and are looking forward to finding them in years to come.
Universe Today has a number of articles including a new class of extrasolar planets found and new techniques for discovering exoplanets.
If you are looking for more information check out NASA's site on extrasolar exploration and Pluto's reclassification.
Astronomy Cast has an episode about extrasolar planets you will want to check out.
Filed under: Astronomy
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