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- SAN FRANCISCO
(Reuters) -
Astronomers scanning distant stars have detected six more
massive planets,
five of which orbit their suns at just the right
distance to support liquid
water and -- theoretically -- life,
scientists announced on Monday.
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- The discoveries brought to 28 the total number of
so-called
"extrasolar" planets found over the past five years
as astronomers
survey hundreds of stars similar to Earth's sun for
signs they may have
planets in tow.
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- Each set of new discoveries
helps to hone scientific
theories about the development of our own
solar system and the possibility
that Earth-like planets may be
found.
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- "Planet hunting is a lot like making wine,"
said
Steven Vogt of the University of California-Santa Cruz, one of the
team
of astronomers collecting and analyzing data provided by Hawaii's
Keck
I Telescope, the sharpest optical telescope in the world.
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- "You have got to
plant the grapes, you have got
to be patient, and at some point they
ripen and are ready for harvest,"
Vogt said. "We have a lot
of star systems that we have been looking
at, and now are ready for
harvest."
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- None of the new planets unveiled on Monday are anything
like
Earth. Instead, they are gaseous giants ranging in size from slightly
smaller to several times larger than Jupiter, the largest planet in our
own solar system.
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- And, like Jupiter, they were seen as extremely inhospitable
to
life themselves -- made up of swirling masses of helium and hydrogen
gasses.
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- But five out of the six are in what astronomers call
the
"habitable zone" which could allow the existence of liquid
water, a prerequisite for life. This makes them different from most of
the extrasolar planets found before this, which have been either to hot
or too cold.
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- "That five out of six of these things are in the
habitable
zones of their stars shows it is not an accident," Vogt
said,
noting that planetary temperatures could range from -38 degrees to
112
degrees Fahrenheit (-39 to 44 degrees Celsius).
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- Hopes for life in these star
systems would focus on possible
moons of the giant gas planets, he
said. Like Jupiter and Saturn, which
have their own rocky satellites,
moons of these planets could conceivably
harbor liquid water and
therefore life, he said.
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- "That is the interesting thing, to think about water
existing on the surface of some moon out there," Vogt said. "It's
pure conjecture, but you can imagine some cave perhaps with water in it
... it is possible."
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- Besides Vogt, the discovery team also included Geoffrey
Marcy of the University of California-Berkeley, Paul Butler of the
Carnegie
Institution of Washington D.C. and Kevin Apps of the
University of Sussex
in England. Their findings will be published in
the Astrophysical Journal.
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- One of the planets, HD 192263, was also recently
detected
by a team in Geneva, Switzerland, the U.S. team said.
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- Planet-hunting
astronomers do not actually see new planets,
but rather detect their
presence by watching for a telltale wobble in the
stars they orbit; the
wobble is caused by the gravitational pull the planets
exert on the
star.
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- Vogt
said the newly found systems were unlikely to harbor
any Earth-like
planets. Jupiter-sized planets in oval-shaped or eccentric
orbits --
instead of the neatly stacked, circular orbits of our solar system
--
would have such gravitational force as to quickly eject any smaller
neighbor, he said.
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- But he said the hunt will continue. With data continuing
to
pour in, scientists are able to calibrate their calculations more
precisely
and detect Jupiter-sized planets further away from their
suns. The goal
is to zero in on systems that roughly match our own,
with large Jupiter-like
planets circling in even orbits far enough away
from the star that smaller,
rocky Earth-like planets could exist closer
in.
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- "In order to detect these guys, you've got to wait
for 11
or 12 years (for enough data). There could be a huge reservoir of
planets out there, but we just don't know it yet,' Vogt said. "That's
one of our Holy Grails. I think they are probably out there. We just have
to be patient. "
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