[Robert A Cook PE]

See, finding any sort of "moon" around Ceres would call for a wholesale "renaming" of several planet-like bodies - which allows Pluto to be kept, add Ceres, add Xena ... etc.

This would keep more people happy, since 9 planets into 11 planets doesn't break any "rules" ....

[SunkenCiv]

Other asteroids are already known to have moons, but the asteroids are not generally spherical, they're just irregular chunks of rock. Having a moon would not help. Mercury and Venus are moonless, and until 1978 (I think that's the year) Pluto was believed to be moonless.

[inquest]

See, finding any sort of "moon" around Ceres would call for a wholesale "renaming" of several planet-like bodies - which allows Pluto to be kept, add Ceres, add Xena ... etc.

Actually there is an asteroid with a "moom" that was imaged by the Galileo probe on its way to Jupiter.

Basically, there is no scientific definition of a planet, because it's not a scientific term. The word is really just a holdover from astrology, which referred to celestial objects, including the moon and sun, that moved through the background constellations (or "houses", in their terminology). The principal of them was the sun - whichever constellation the sun was in when you were born is your "sign". But the other planets had their own special powers or whatever depending on their absolute and relative locations ("When the moon is in the seventh house, and Jupiter aligns with Mars" and all that).

[Richard Kimball]

My grandmother, who was born in the 1800's reminded me of the temporary nature of much of what we scientifically "know." She mentioned a couple of times that most scientific discussions should end with "we think." One of the examples she gave me was that when she was in school, they were taught that there were seven planets. Back in the 1960's, she told me there were probably more planets than nine.

My grandmother was born in 1894 and died in the 1970's. She read about the Wright brother's flight when it was current news, and saw the first moon landing. Altogether, that was an incredible time to be alive.