RAS: Watery, rocky planets may be common in the Milky Way

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RAS: Watery, rocky planets may be common in the Milky Way

Post by bystander » Tue Apr 13, 2010 12:35 am

Watery, rocky planets may be common in the Milky Way
Royal Astronomical Society Press Release
RAS PN 10/22 (NAM 7) 13 April 2010
An international team of astronomers have discovered compelling evidence that rocky planets are commonplace in our Galaxy. Leicester University scientist and lead researcher Dr Jay Farihi surveyed white dwarfs, the compact remnants of stars that were once like our Sun, and found that many show signs of contamination by heavier elements and possibly even water, improving the prospects for extraterrestrial life.
Rocky Planetesimals as the Origin of Metals in DZ Stars
An analysis of the calcium and hydrogen abundances, Galactic positions and kinematics of 146 DZ stars from the Sloan Digital Sky Survey demonstrates that interaction with the interstellar medium cannot account for their externally polluted atmospheres. The calcium-to-hydrogen ratios for the 37 DZA stars are dominated by super-solar values, as are the lower limits for the remaining 109 DZ stars. All together their metal-contaminated convective envelopes contain 10^{20+-2} g of calcium, commensurate with the masses of calcium inferred for large asteroids. It is probable that these stars are contaminated by circumstellar matter; the rocky remains of terrestrial planetary systems. In this picture, two predictions emerge: 1) at least 3.5% of all main sequence A- and F-type stars build terrestrial planets; and 2) the DZA stars are externally polluted by both metals and hydrogen, and hence constrain the frequency and mass of water-rich, extrasolar planetesimals.
Stellar 'pollution' may be remains of watery planets
New Scientist - 13 Apr 2010
A generation of planets may now be no more than a whiff of pollution in the atmospheres of their dead parent stars. If so, it would suggest that rocky planets are common, and hints that most such planets have water.

White dwarfs – the dense remnants of ordinary stars – usually have very pure atmospheres dominated by the lightweight elements hydrogen and helium; heavier elements tend to sink into a star's interior. But about 20 per cent of white dwarfs are tainted by traces of heavier elements.
Earth-Like Planets May Abound in the Milky Way
Science Now - 12 Apr 2010
Maybe Frank Drake was right. Nearly half a century ago, the American astronomer postulated that, based on pure statistical probability, the Milky Way could be teeming with Earth-like planets. Now observations of formerly sunlike stars called white dwarfs suggest that the overwhelming majority of them once harbored at least one rocky world. And because sunlike stars could account for up to half of the Milky Way's population of several hundred billion suns, that means hundreds or even thousands of civilizations might inhabit our galaxy.
Polluted Old Stars Suggest Earth-like Worlds May Be Common
Space.com - 12 Apr 2010
Earth-like planets should be a fairly common feature of other solar systems in our galaxy, a new study of stellar senior citizens suggests.

More than 90 percent of stars in the Milky Way, including our own sun, end their lives as a white dwarfs. Traditionally, these dense stellar remains haven't been the first place that astronomers look for signs of planets outside our own solar system. Instead, exoplanet searches have focused on stars like our own sun.

But tantalizing new results suggest that these elderly stars might also be a rich source of information on the potential for other planetary systems out there in the galaxy.