It's Official: Eris More Massive Than Pluto

According to a report in Science, Eris, the icy body discovered beyond Pluto in 2005, is officially more massive than Pluto.

The discovery of Eris led to a debate about what constitutes a planet, which eventually caused Pluto to be demoted from planet to dwarf planet.

Mike Brown of the California Institute of Technology, using Hubble and the Keck Observatory in Hawaii to observe the orbit of Eris’s moonlet, Dysnomia, has determined that Eris’s mass is 1.27 times the mass of Pluto. This confirms previous Hubble observations that showed that Eris is physically slightly larger than Pluto.