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virus: Astronomers Find Oldest Planet Yet
« on: 2003-07-13 16:39:40 » |
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Astronomers Find Oldest Planet Yet
Jul 10, 10:19 PM (ET)
By PAUL RECER
WASHINGTON (AP) - Astronomers said Thursday the oldest and most distant
planet yet found is a huge, gaseous sphere 13 billion years old and
5,600 light years away, a discovery that could change theories about
when planets formed and when life could have evolved.
The planet, more than twice the size of Jupiter, orbits two stars, a
pulsar and a white dwarf that linked together about a billion years ago.
The system is in the constellation Scorpius within a globular cluster
called M4 that contains stars that formed billions of years before the
sun and its planets.
"All of the stars in this cluster are about the same age, so the
presumption is that the planet is that age also," Harvey Richer, an
astronomer at the University of British Columbia in Vancouver, Canada,
said Thursday at a NASA news conference.
The pulsar, a rapidly spinning star, was discovered in M4 about 15 years
ago. Astronomers shortly afterward found that it was gravitationally
bound to a white dwarf, the remnants of an ancient, sunlike star that
had exhausted its hydrogen and helium fuel. There was suspicion that yet
another body was orbiting nearby, but the planet was not discovered
until astronomers studied data from the Hubble Space Telescope.
Alan Boss, an astronomer at the Carnegie Institution in Washington, said
finding such an ancient planet is a "startling revelation" because it
means that planets could have formed within a billion years after the
big bang, far earlier than most theories have stated.
"This means that 13 billion years ago, life could have arisen and then
died out," said Boss. "This has immense implications."
Astronomers in recent years have found 107 other extra-solar planets -
planets outside of the solar system - but all of those are about the
same age or just slightly older than the sun, 4.5 billion years.
It was thought that planets could not form until there had been at least
one generation of stars after the Big Bang because the planet building
requires heavier elements, such as carbon, silicate and iron. These
elements, called "metals" by astronomers, are thought to have formed
during the life cycle of the early stars, when hydrogen and helium were
burned in fusion fires.
The sun is a third-generation star, but the M4 stars are believed to be
in the first generation after the Big Bang, some 14 billion years ago.
Boss said the solar system has about 30 times as many heavier elements
as M4.
Harvey said the discovery suggests that astronomers should now search
for planets in the more ancient star fields, which includes systems like
the M4 globular cluster.
"The door is open now to start looking in the metal-poor clusters," he
said.
Steinn Sigurdsson, a professor of astronomy at Pennsylvania State
University, said that based on orbital measurements and other data,
astronomers can infer a history for the M4 planet.
He said it is believed the planet formed about a sunlike star near the
edge of the globular cluster. Over time, the star and its planet were
gravitationally captured by the pulsar, which was then a neutron star
with another star as a companion. As the sunlike star was sucked into
the mix, the companion star was ejected from the group. This left the
sunlike star and neutron star bound to each other while the planet
orbited both.
Eventually, the sunlike star burned up its fuel, bloomed into a red
giant and then collapsed into a white dwarf. The neutron star, with its
greater density, sucked in material from the collapsing star. This
caused the neutron star to start spinning at 100 times a second and
emitting radio signals, turning into a pulsar. It was the clocklike
pulsing of these radio signals, picked up by radio telescopes, that led
to other observations and the discovery of the complex.
Sigurdsson said there were enough heavy elements in the M4 complex to
have formed some terrestrial planets, like Earth and Mars, in orbit of
the sunlike star. He said it is theoretically possible that life could
have formed on those planets some
12.5 billion years ago.
But when the sunlike star was pulled into orbit of the neutron star, any
planets near the sun would have been destroyed. Only the gaseous planet,
orbiting some two billion miles out, would have survived.
"Over a billion years ago, any near-in planet would have been wiped
out," said Sigurdsson. "But it could have been stable for 10 billion
years before," plenty of time for intelligent life to have formed.
If there was intelligent life on such a planet, he said, it was
destroyed as the parent sun was pulled toward the neutron star.
"They would have seen it coming," Sigurdsson said of creatures that may
then have been living on that planet.
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On the Net:
NASA: http://www.nasa.gov
Space Telescope Science Institute: http://hubblesite.org/news/2003/19
--
Walter Watts
Tulsa Network Solutions, Inc.
"Reminding you to help control the human population. Have your sexual
partner spayed or neutered."
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