A New Solar System - 12 Planets!

Thursday, August 17th, 2006 at 10:43 AM by Dave

Wow! The International Astronomical Union (IAU) has submitted to its membership a new set of definitions for planets and smaller solar system bodies. They are now called “Planets” and “Plutons”, or pluto-like bodies. Please see the IAU text, http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601_release.html

Planets are defined as “a large and round body”. This implies that the planet Pluto and its moon, Charon, fit in this category. The asteroid, Ceres, also fits the definition of a planet. The new object UB313 also fits this new definition of a planet. This gives us 12 planets with this new definition.

The roundness of a planet comes from a sufficient enough gravity to cause it to overcome its natural rigidity. This would imply that our Moon (Luna) might also be classified as a planet. However, the center of gravity between the Moon and Earth lies beneath the Earth’s surface. This makes the Moon a satellite of the Earth. The center of gravity between Pluto and Charon lies between the two of them in space, making a double planet system.

If you want to find out where I stand on this issue, read my previous post and read between the lines (I think there are only 8 planets). I think that objects beyond the orbit of Neptune are Kuiper Belt objects and are not planets. However, I don’t have a vote in the matter.

The IAU has to vote on these definitions later this month. Watch for a further update.

Posted in Astronomy News

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