An artist's concept depicts the distant dwarf planet known as Eris. Calculations published on June 14, 2007 show Pluto,the distant world that astronomers no longer deem a planet, is not even the largest of our solar system's so-called dwarf planets -- it is smaller than the recently discovered dwarf planet Eris.(Xinhua/Reuters Photo)

    BEIJING, June 15 (Xinhuanet) -- Eris,the dwarf planet that effectively kicked Pluto out of its planethood, is not only bigger than the former ninth planet, but also much more massive, according to a new study published on Thursday.

    Michael Brown, a planetary scientist, and his graduate student Emily Schaller of the California Institute of Technology used data collected from the Hubble Space Telescope and the Keck Observatory in Hawaii to determine for the first time that Eris had a greater mass than Pluto.

    Eris, named for an ancient Greek goddess of strife and discord and discovered in 2005, is 27 percent more massive than Pluto according to their research. Eris is about half the size of Earth's moon, Brown said. Eris circles the sun from about 9 billion miles away -- about twice the distance of Pluto at the farthest point in its orbit.

    Pluto, was discovered in 1930 and named for the ancient Greek god of the underworld. At the time, it was assumed that Pluto was the largest of these so-called dwarf planets, but now comes word that Pluto runs a distant second to Eris, a similar astral body in the Kuiper belt.

    In order to determine Eris' mass, the researchers used the Hubble Space Telescope and the Keck Observatory to calculate the orbital speed of its moon, Dysnomia. According to Newtonian physics, the more massive a celestial object is, the faster its satellite will zip around it. It is believed that Dysnomia is less than 100 miles (150 km) across and it takes about 16 Earth-days to make one trip around Eris.

    "So by looking at the time it takes the moon to go around Eris, we're able to calculate the mass," Schaller said. Eris itself is believed to have a diameter of 1,490 to 1,860 miles (2,400 to 3,000 km)." To put that into perspective, if you took all the asteroids in the asteroid belt (between Mars and Jupiter) and multiplied by four, they would easily all fit into Eris," Schaller said. Pluto has a diameter of about 1,430 miles (2,300 km) across.

    The new study also suggests that like Pluto, Eris is likely made up of ice and rock.

    (Agencies)