[X] My Assistant

[Holder of the Tw...]

The fifth planet in the solar system is ... CERES!

So says the draft from the IAU working committee that is trying to settle the question of the definition of a planet. And the agreement on the committee was unanimous.

I knew it. I knew it all along. First time I ever saw Ceres I thought "Yep, that's a planet". Although admittedly my trusty astroscan couldn't quite resolve it.

I would have fought for Vesta and Pallas, too. But this is good enough.

Oh, incidently, Pluto is too. So is 2003UB313.

Well now, that should give a little extra insurance to the DAWN mission getting of the ground.

This all has to be voted on by the whole body, but once again, the committee was unanimous, all seven members. Anything round by gravity, roughly above 850 km diameter.

[alan]

What rule excludes the other larger KBOs and Sedna? Is it just a question of illumination?

I don't believe Sedna and the others candidates's diameters have been determined precisely enough for the IAU to certain they meet the criteria. For example, if Sedna had the same albedo as Pluto it would be too small to meet the criteria.

[ngunn]

I don't believe Sedna and the others candidates's diameters have been determined precisely enough for the IAU to certain they meet the criteria. For example, if Sedna had the same albedo as Pluto it would be too small to meet the criteria.

Thanks, Alan. Presumably we don't yet know how 'round' they are either.

[punkboi]

Thanks, Alan. Presumably we don't yet know how 'round' they are either.

Ceres won't be a planet. What a letdown