Posted: Mon, Jun 18, 2007, 8:13 AM ET (1213 GMT)
Planetary scientists have found that the dwarf planet Eris, located in the distant Kuiper Belt, is more massive than Pluto, the former planet that was downgraded last year. In a paper published in the current issue of the journal Science, Caltech researchers used observations of Eris, originally designated 2003 UB313, and its moon Dysnomia made by the Hubble Space Telescope and the Keck Observatory. Those observations were used to measure the mass of Eris, which is 27 percent more massive than Pluto. Eris was previously found to be larger in diameter than Pluto.

Related Links:

•  Sky and Telescope article
•  AP article
•  ScienceNow article
•  SPACE.com article
•  Caltech press release