Astronomers have detected what could be the Solar System's 10th planet. It was first seen by astronomers using California's Mount Palomar Observatory, and has been given the name "Sedna" after the Inuit goddess of the ocean. Observations show it measures about 1,180-2,360km (730-1,470 miles) across, making it similar in size to Pluto. Astronomers now say they have evidence that Sedna has its own moon, although this needs to be confirmed, and is also very red in colour. There is likely to be some debate about whether it qualifies as a true planet, but some scientists are already saying it re-defines our Solar System.

 

http://news.bbc.co.uk/1/hi/sci/tech/3511678.stm

Wicked nifty! Tell me, has anyone explained the perturbations in Neptune's orbit? I know Pluto is way too small to cause them, that's for sure.

Wow. Makes you wonder if there are more planets floating around our solar system...

I dunno, we would have to establish a long-long-term mission to get a sattelite out there to check it out. Or at least get a closer look.