Image via Wikipedia
According to the International Astronomical Union (IAU), there are eight planets. These planets include Mercury, Venus, Mars, Neptune, Jupiter, Saturn, Uranus and Earth. Are you wondering what happened to Pluto?
Pluto is considered a dwarf planet. There are five dwarf planets, including Ceres, Haumea, Makemake, Eris and Pluto. This was clarified in August 2006. These five planets were potentially going to be considered IAU planets, but the definition of a planet was clarified with a formal defined by the IAU.
The IAU determined that a planet must have three qualifications in order to be considered a planet in the Solar System. First, it must orbit around the sun. Secondly, it must be big enough to be gravitationally dominant in it’s own orbit, so that no other large bodies are in the “neighborhood.” Thirdly, the planet must be large enough to be round (or, at least, almost round). If the planet does not meet all three of these qualifications, it’s considered a dwarf planet.
Not everyone agrees with this classification, of course. Some say that not all of the planets have actually cleared their own neighborhoods, for example. Many astronomers refuse to follow the classification. Also, scientists like Mike Brown say there are actually lots and lots of “dwarf planets” out there, soon to be discovered.
Naturally, many people in the non-scientific community have had trouble letting go of Pluto as a planet. Remember grade school? Or, perhaps the 1930′s discovery. Also, when Eris was first discovered it was called the “tenth planet” which has lead to much media attention and some confusion. Still, at this point, there are officially nine planets.
