Pluto outshone yet again
2007-06-15 11:07
Chicago - Call it strike two for Pluto.
Just last year the icy, enigmatic planet got kicked out of the brotherhood of planets and demoted to the status of an also-ran or dwarf planet.
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.
A new analysis by US astronomers shows that Eris is in fact 27% bigger than Pluto, a finding that will bolster the International Astronomical Union's controversial 2006 decision to reclassify Pluto, ending its longstanding position as the ninth planet in the solar system.
"This was Pluto's last chance to be the biggest thing found so far in the Kuiper belt," said Michael Brown, a professor of planetary astronomy at the California Institute of Technology (Caltech) in Pasadena, California.
"There was a possibility that Pluto and Eris were roughly the same size but these new results show that it's second place at best for Pluto."
Brown and a Caltech graduate student Emily Schaller calculate that Eris weighs in at 16.6 billion trillion kilograms, according to a report of their findings published in the journal Science.
Made up of ice and rock
The pair were able to measure the mass of Eris by determining the Keplerian orbit of Eris' satellite Dysnomia using data from the Keck Observatory and the Hubble Space Telescope.
The new data also suggests, that like Pluto, Eris is likely made up of ice and rock.
"Pluto and Eris are essentially twins except that Eris is slightly the pudgier of the two," said Brown. "And a little colder," added Schaller.
Based on spectral data, the researchers think that Eris is covered with a layer of methane that has seeped from the interior and frozen on the surface.
As in the case of Pluto, the methane has undergone chemical transformations, probably due to the faint solar radiation, causing the methane layer to redden.
But the methane surface on Eris is somewhat more yellowish than the reddish-yellowish surface of Pluto, perhaps because Eris is farther from the sun.