AAS 2009: Glowing graveyards
The glowing graveyard of rubble that surrounds some dying 'white dwarf' stars is providing astronomers with clues to the composition of rocky extrasolar planetary systems. By looking at the faintly glowing, shredded remnants of asteroids that surround distant white dwarfs, astronomers at the University of California at Los Angeles are finding that they have similar chemical compositions to rocky planets and asteroids closer to home – in the inner solar system. “We have a tool for measuring the bulk composition of the planets,” UCLA's Michael Jura said at a AAS press conference on Monday. “It strengthens suspicions that Earth-like planets are common.”
Geologists, Jura says, have long known that the Earth is rich in silica minerals, but poor in carbon, relative to the overall chemical composition of the sun. But whether that discrepancy holds elsewhere in the universe has been, until recently, a mystery. “Astronomers tend not to think about this,” he says. Using the Spitzer Space Telescope, Jura and others have assembled a small catalog of white dwarf stars that have rubble disks that glow brightly enough so that astronomers can tease out chemical compositions from their spectra. The latest white dwarf system, presented on Monday, brings the total up to eight.
Jura showed a spectrum with a clear bump in the prevalence of silicate minerals – and a lack of carbon. This means that the inner solar systems of extrasolar systems might not be terribly different from our own. Jura's work has been accepted for publication in the Astrophysical Journal.
Image: NASA/JPL-Caltech/M.Jura
