[meteorite-list] NASA's Hubble Space Telescope Finds Dead Stars 'Polluted' With Planet Debris

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 9 May 2013 10:33:49 -0700 (PDT)
Message-ID: <201305091733.r49HXnY8014789_at_zagami.jpl.nasa.gov>

May 09, 2013

J.D. Harrington
Headquarters, Washington
j.d.harrington at nasa.gov

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
villard at stsci.edu

RELEASE: 13-133


WASHINGTON -- NASA's Hubble Space Telescope has found the building
blocks for Earth-sized planets in an unlikely place-- the atmospheres
of a pair of burned-out stars called white dwarfs.

These dead stars are located 150 light-years from Earth in a
relatively young star cluster, Hyades, in the constellation Taurus.
The star cluster is only 625 million years old. The white dwarfs are
being polluted by asteroid-like debris falling onto them.

Hubble's Cosmic Origins Spectrograph observed silicon and only low
levels of carbon in the white dwarfs' atmospheres. Silicon is a major
ingredient of the rocky material that constitutes Earth and other
solid planets in our solar system. Carbon, which helps determine
properties and origin of planetary debris, generally is depleted or
absent in rocky, Earth-like material.

"We have identified chemical evidence for the building blocks of rocky
planets," said Jay Farihi of the University of Cambridge in England.
He is lead author of a new study appearing in the Monthly Notices of
the Royal Astronomical Society. "When these stars were born, they
built planets, and there's a good chance they currently retain some
of them. The material we are seeing is evidence of this. The debris
is at least as rocky as the most primitive terrestrial bodies in our
solar system."

This discovery suggests rocky planet assembly is common around stars,
and it offers insight into what will happen in our own solar system
when our sun burns out 5 billion years from now.

Farihi's research suggests asteroids less than 100 miles (160
kilometers) wide probably were torn apart by the white dwarfs' strong
gravitational forces. Asteroids are thought to consist of the same
materials that form terrestrial planets, and seeing evidence of
asteroids points to the possibility of Earth-sized planets in the
same system.

The pulverized material may have been pulled into a ring around the
stars and eventually funneled onto the dead stars. The silicon may
have come from asteroids that were shredded by the white dwarfs'
gravity when they veered too close to the dead stars.

"It's difficult to imagine another mechanism than gravity that causes
material to get close enough to rain down onto the star," Farihi
By the same token, when our sun burns out, the balance of
gravitational forces between the sun and Jupiter will change,
disrupting the main asteroid belt. Asteroids that veer too close to
the sun will be broken up, and the debris could be pulled into a ring
around the dead sun.

According to Farihi, using Hubble to analyze the atmospheres of white
dwarfs is the best method for finding the signatures of solid planet
chemistry and determining their composition.

"Normally, white dwarfs are like blank pieces of paper, containing
only the light elements hydrogen and helium,"Farihi said. "Heavy
elements like silicon and carbon sink to the core. The one thing the
white dwarf pollution technique gives us that we just won't get with
any other planet-detection technique is the chemistry of solid

The two "polluted" Hyades white dwarfs are part of the team's search
of planetary debris around more than 100 white dwarfs, led by Boris
Gansicke of the University of Warwick in England. Team member Detlev
Koester of the University of Kiel in Germany is using sophisticated
computer models of white dwarf atmospheres to determine the
abundances of various elements that can be traced to planets in the
Hubble spectrograph data.

Farihi's team plans to analyze more white dwarfs using the same
technique to identify not only the rocks' composition, but also their
parent bodies.

For more information about NASA's Hubble Space Telescope, visit:

Received on Thu 09 May 2013 01:33:49 PM PDT

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