For several years, UCLA astronomers have studied GD 362, a peculiarly dirty white dwarf star 165 light-years away in the constellation Hercules. Now they are pretty sure why the atmosphere of this dense, hot but slowly cooling ghost of a once much larger star is so polluted. It ate a planet.
“We probably have a destroyed world here,” says Michael Jura, coleader of the UCLA team. Apparently a planet with the mass of Mars — a billion trillion metric tons or so of rock, iron, dissociated water and other ingredients — was dismembered and atomized, its remains now bobbing in the thin but dense, 10,000 kelvins atmosphere that GD 362’s powerful gravity holds close around itself.
Like a specimen on the ultimate autopsy table, the supposed planet has its insides spread wide for inspection. It would thus appear to provide science its first look at the composition of an alien, rocky and roughly Earthlike planet in an exosolar planetary system. In fact, the material marring GD 362 appears to closely match what you would get by grinding up Earth, Mars or Venus, the UCLA team and collaborators report in a paper to appear in The Astrophysical Journal.
The report provides some of the first hard data for a nascent field of science — let’s call it terrestrial exoplanetology —inching ever closer to the day when Earthlike planets might finally be visible directly to ever more powerful telescopes planned for construction on Earth and for orbit. Viewing white dwarfs with such instruments may tell astronomers whether rocky planets orbiting other stars all resemble Earth or come in diverse varieties.
“We have a unique tool for studying extrasolar planetary composition,” Jura says. “If we are clever enough, we might even know something about their structure, not just their bulk ingredients.”
The UCLA team has an additional dozen or so polluted white dwarfs under study. So far, all look as though they contain similar stuff.
http://www.sciencenews.org/view/feature/id/45184/title/The_Star_That_Ate_a_MarsAwesome.
Topic: Dwarf Eats Planet!