Blame it on the International Astronomical Union. They set up strict regulations for objects in our Solar System. They were organized in 1919 and made it their mission on this Earth to safe guard all astronomical research. In 2006 the organization finally decided to make a final decision about the definition of a planet, which is:
1. The object must orbit the Sun by itself.
2. The object must have enough mass to create enough gravity to make it a fairly round object.
3. It's neighborhood must be clear of debris. This means that a planet has to be large enough to dominate it's orbit around the Sun and keep it clear of other objects.
Pluto isn't large enough to clear its neighborhood of objects. Moons are not called planets either. Even big moons larger than Earth, if they still orbit another planet. Nope...not a planet. At first a bunch of people were SUPER mad that Pluto was downgraded to a dwarf planet.
Some time has passed, but now we understand that the International Astronomical Union had to make strict rules because we are seeing galaxies farther and farther away and scientists needed to know, for sure, if they were looking at a planet, a moon, or a dwarf planet. The categories may even change again as our observations get better and better.
Setting boundaries is really the best way....
Im really sad that pluto is not a planet
ReplyDeleteR.I.P. Pluto.
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