In 2005 the object now called Eris was considered to be possibly the 10th planet of our solar system. This caused chaos (hence the name) in astronomical circles... and finally an IAU decision came about which declassified Pluto as a planet and hence Eris was not known as a planet. They are both known as dwarf planets, along with Ceres (largest object in the asteroid belt). Anyway, recently astronomers using NASA's Hubble Space Telescope and the W.M. Keck Observatory have precisely measured the mass of Eris. Eris is 1.27 times the mass of Pluto, formerly the largest member of the Kuiper Belt of icy objects beyond Neptune. In the images released by NASA Eris and its "moon" Dysnomia can be see:
Credit: NASA, ESA, and M. Brown (California Institute of Technology)
For more see: [HubbleSite NewsCenter]
