[meteorite-list] Old star shows signs of Earthlike planets

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Thu, 16 Aug 2007 23:52:49 -0400
Message-ID: <ho6ac39iqe65j2h0468g2j85h9scbiab3l_at_4ax.com>

Old star shows signs of Earthlike planets
Distant asteroid's chemical signature is similar to Earth's, astronomers say

WASHINGTON - Chemical elements observed around a burned-out star known as a
white dwarf offer evidence that Earthlike planets once orbited it, suggesting
that worlds like our own may not be rare in the cosmos, scientists said
Thursday.

Astronomers at the University of California at Los Angeles and University of
Kiel in Germany studied a white dwarf called GD 362, located 150 light-years
away in our Milky Way galaxy.

They figured out the chemical composition of a large asteroid that was ripped
apart by gravitational forces as it approached GD 362, finding it was similar to
that of Earth?s crust. It was rich in iron and calcium and low in carbon, much
like a strong rock, they said.

The white dwarf is surrounded by dusty rings, probably made up of objects
shredded as they ventured too close.

?It?s probably quite similar to Saturn?s rings,? UCLA astronomer Michael Jura
said in a telephone interview.

GD 362 once was a star similar to the sun. After billions of years, it ballooned
into a ?red giant? as part of its death process, expelling most of its outer
material, then degenerated into a burned-out white dwarf.

The fact that the asteroid is so similar in makeup to the Earth, as well as the
moon, indicates that rocky planets like our own may have orbited the star eons
ago, Jura said. And if such planets currently populate our solar system and
existed in a planetary system around this white dwarf, they may well be fairly
common in the universe, he added.

Extraterrestrial life?
The research, based on observations made using the Keck I Telescope in Hawaii,
will appear in the Astrophysical Journal. It is the latest evidence found by
astronomers indicating that planets like Earth are found outside our solar
system.

European astronomers in April said they detected the most Earthlike planet yet
outside the solar system orbiting a star 20.5 light-years from here, with
temperatures that could harbor water and perhaps life.

A light year is about 6 trillion miles, the distance light travels in a year.

Jura said that his study?s fresh evidence of Earthlike planets outside our solar
system lends support to the possibility of extraterrestrial life.

?It?s more than just daydreams,? Jura said. ?It?s realistic to imagine that
there are other places relatively similar to the Earth which would be a habitat.
But, of course, we have no evidence whatsoever that they (alien life forms) do
exist.?

The rocky asteroid had a diameter of roughly 125 miles (200 kilometers) and may
have been smashed by GD 362 between 100,000 and a million years ago, the
astronomers said. While the white dwarf has a mass close to that of our sun, it
has collapsed to such a point that its diameter is approximately that of the
Earth.

GD 362 may offer a glimpse into our solar system?s future. Astronomers believe
the sun in perhaps 5 billion years will go through the same process, ending up
as a white dwarf.

UCLA astronomer Benjamin Zuckerman said when our sun starts to expand in size
and lose mass, the planets closest to the sun, Mercury and Venus, will get
engulfed and destroyed. Other planets, probably including Earth, and the
asteroid belt between Mars and Jupiter, will spiral out of their orbits,
Zuckerman said.
Received on Thu 16 Aug 2007 11:52:49 PM PDT