Still-unnamed, a bright new planet has been found in the outer solar system. This one is at about 51 A.U. distance from the Sun, but comes in as close as 35 AU. That average is further than Quaoar (discovered in 2002), but considerably closer than Sedna, discovered last year. The new minor planet, numbered 2003 EL61 was actually first observed in 1955; its very slow orbital motion was only noticed in observations made in 2003 and 2004. It was also a little harder to find as it orbits in a plane 28 degrees away from the ecliptic, where most other solar system objects are.

According to the BBC, size is estimated between 1500 and 2300 km diameter (Pluto’s diameter is 2270 km). The New Scientist article claims it could be twice as large as Pluto, if the surface is as dim as the average for such objects.

Update [2005-7-29 15:28:43 by apsmith]: This article claims the mass of the object has been pinned down – through the discovery of a moon! Mass comes out at about 32% of Pluto’s, so probably 70% the diameter. Not quite as big then, but the biggest thing found out there so far.

Update [2005-7-31 9:18:15 by apsmith]: This article from Science Daily indicates there’s another distant minor planet that is likely actually larger than Pluto: 2003UB313, at 97 AU right now. “We are 100 percent confident that this is the first object bigger than Pluto ever found in the outer solar system.”