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Location: UFOUpDatesList.Com > 1999 > Feb > Feb 1

Astronomers Seek Another Earth

From: Stig Agermose <stig.agermose@get2net.dk>
Date: Sun, 31 Jan 1999 19:26:12 +0100 (MET)
Fwd Date: Mon, 01 Feb 1999 10:26:49 -0500
Subject: Astronomers Seek Another Earth


[List only]

Source: Christian Science Monitor Service via the Nando Times,

http://www.nandotimes.com/noframes/story/0,2107,13186
-22254-156364-0,00.html

Stig

***

Astronomers search for another Earth 

Copyright =A91999 Nando Media Copyright =A91999 Christian Science
Monitor Service

By ALEX SALKEVER 

HONOLULU (January 31, 1999 11:31 a.m. EST
http://www.nandotimes.com) - For thousands of years, humans have
thought about and searched for worlds outside our solar system -
for planets like ours that can support life.

But since the advent of modern astronomy centuries ago,
detection of distant planets has proved to be as difficult as
finding grains of sugar on a beach. Stars, billions of times
more brilliant than the worlds that circle them, make planets
all but impossible to find. And decades of intense observation
yielded only false alarms, earning planet-hunting a reputation
as a backwater of astronomy.

During the past three years, however, this perception has
radically changed. Through advances in technology, an improved
understanding of planetary behavior and increased access to
better telescopes, astronomers have found 17 planets since 1995.
These discoveries have revolutionized planetary science, forcing
scientists to revise long-held theories about the universe and
making planet-searching one of the hottest fields of astronomy.

"The major change has been access to large telescopes like the
Keck 1/8a telescope in Hawaii with a mirror 30 feet across 3/8,"
says William Cochran, an astronomer at the University of Texas
at Austin. "With big scopes, you get a lot more light. And the
faster you can get light, the faster you can detect these
planets."

In many ways, the recent discovery of what could be a nascent
solar system 220 light years from Earth is a symbol of this
planet-hunting renaissance. Images of the would-be solar system
were first captured by the Keck telescope. Later, using the
Hubble Space Telescope, University of Hawaii astronomer Bradford
Smith discovered that there might be a planet within the new
solar system. He found the planet by searching the heavens in a
different way - by looking at disks of dust around stars.

He sifted infrared images of the star 220 light years away,
dubbed HR 4796A. Inside its disk sat a ring that looked like
hula hoop. "When we pulled the image of this star ring up on the
computer screen, it looked like Saturn," Smith says. "It was
like, 'Wow!' We had not really expected that."

The same image that floored Smith brought a room full of
normally sedate astronomers to their feet for a standing ovation
at the American Astronomical Society meeting earlier this month.

Indeed, the find is a breakthrough. According to previous
theories, no planetary candidate should be there. The star is
only 8 million to 10 million years old, supposedly far too young
to have developed a large, far-flung planet like the one
indicated in the Hubble images.

But that's really no great surprise. Beyond the quixotic object
found by Smith in the gloaming of deep space, astronomers are
finding other planets that do not conform to traditional models.

For one thing, many are massive - as large as Jupiter but with
short orbits closer to their host stars than Mercury is to the
sun. Theoretically, Jupiter-like planets were supposed to be
found orbiting farther away from their host stars, where they
would not be sucked in by the stellar bodies' strong
gravitational pull.

Many of the newly discovered planets were also found to have
elliptical orbits - unlike those of planets in our solar system,
which are largely circular.

Theorists are now scrambling to rebuild planetary theory based
on these observations. They have already come up with some
explanations. "Hot Jupiters" might be migrating toward their
host stars, destroying other planets that lay in their paths,
scientists say. Meanwhile, the elliptical orbits of extrasolar
planets might be caused by the gravitational pull of either a
nearby star or planet.

In addition to learning more about planets themselves,
scientists have learned more about how to look for them. Before
the binge in planetary discovery, money to finance planet
searches was hard to come by. "For a long time, whenever anyone
asked for money to find planets, everybody laughed and threw
their proposal away," says William Borucki, a researcher at the
NASA/Ames Research Center in California.

Then in October 1995, two astronomers in Switzerland noticed
that the light spectrum of the star 51 Pegasi was wobbling. Upon
closer examination, the scientists concluded that the phenomenon
was caused by a large planet orbiting very close to the star.
After that, the wobble - previously only a theory - became a
telltale sign for planet hunters and helped resuscitate the
field.

In fact, new research shows that 5 percent of the stars surveyed
show evidence of planets.

Still, astronomers are far from a consensus that an Earth-like
body exists. "It is still being argued today by many people that
our own solar system is an absolute anomaly," says Smith. "On
the other side of it, there are many people who believe that
when you form stars you form planets at the same time."

In the next decade, a new generation of highly sensitive
telescopes will turn their mirrors heavenward. Most will
dedicate sky time to planet searches. Scientists are also
perfecting new techniques that use less-expensive equipment to
locate planets. And direct imaging of distant stars with
infrared instruments promises to produce more snapshots of stars
and planets, too.

But all these new high-powered tools still can only give
scientists evidence that planets exist - they cannot give a
direct picture of an Earth-like planet. "The problem is
Earth-like planets are small and whatever effect they have is
going to be much more difficult to detect," Smith says. 


Copyright =A91999 Nando Media


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