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3 planets found around distant star
Discovery raises hopes for solar systems like our own

By Alan Boyle

WASHINGTON, April 15 -  Building on 11 years of observations, 
astronomers say three giant planets have been detected around a 
sunlike star 265 trillion miles away - representing the first planetary 
system that scientists think could be like our own.

       THE TRIPLE DETECTION, announced Thursday by a team of 
seasoned planet-hunters, adds new glimmers of hope to the search for 
Earthlike planets and perhaps even extraterrestrial life. It firms up the 
argument that these worlds are indeed planets rather than brown dwarfs 
or captured stars. But it also poses new puzzles.

       "Today, with the discovery of the first planetary system beyond our
own, we are witnessing the emergence of a new era in human exploration,"
declared Geoffrey Marcy, an astronomer at San Francisco State University
and one of the system's discoverers. Just as past cultures looked from 
their own lands across seas and skies, earthlings were now beginning "a
reconnaissance, if you will, of planets around other stars," he said.

       Marcy and his longtime colleague in the search for extrasolar
planets, R. Paul Butler of the Anglo-Australian Observatory, detected the
first planet around Upsilon Andromedae in 1996, using what has become 
a standard method: They tracked a pattern of Doppler shifts in the 
spectrum of light from the star, which hints at a wobble caused by the gravitational pull of the circling planet. About 20 distant worlds have been 
detected in this manner.

       In the case of Upsilon Andromedae, there was an extra wobble, even
after the first planet's gravitational pull was taken into effect. Butler, Marcy and other researchers from San Francisco State, the Harvard-Smithsonian 
Center for Astrophysics and the High Altitude Observatory in Boulder, 
Col.,  determined that the extra wobble could only be explained by the 
presence  of two additional planets. A computer simulation confirmed that 
the orbits could be stable.

       The researchers said they have submitted a paper on the subject to
the Astrophysical Journal, drawing on observations made from the Lick
Observatory in California and the Whipple Observatory in Arizona


       Some skeptics have wondered whether the solitary objects 
detected using the Doppler method might actually be brown dwarfs or 
failed stars rather than planets. But the fact that three such objects were 
detected circling the same star should ease that second-guessing, said 
Charles Beichman, chief scientist for the Origins program at NASA's Jet 
Propulsion Laboratory.

       "It's just so spectacular, because in science we say, 'Well, we think
it's like this.' But there is no substitute for really demonstrating that
you're right," he told MSNBC.

       The researchers said the new findings suggest that planetary 
systems like our own are abundant among the 200 billion stars in our 
galaxy alone. Butler said this was just the start of what he expected 
would become a huge database of distant solar systems.

        "Maybe what we have here is a Rosetta Stone that will eventually
explain how these planets are formed," he said.


       Upsilon Andromedae is 44 light-years away, with each light-year 
equal to about 6 trillion miles. It is in the same class as our sun, roughly
two-thirds as old, and is visible to the naked eye.

       The innermost of the three planets was the first one detected: It's
at least three-quarters the mass of Jupiter and completes an orbit every 
4.6 Earth days, circling only 6 million miles away from the star.

       That would make the innermost planet far too hot to support life. But
the middle planet, with at least twice the mass of Jupiter, is about as far
away as Venus is from our own sun, following a 242-day elliptical orbit.
Under the right conditions, Beichman figures the temperature on a moon 
of that planet could vary between 60 and 140 degrees Fahrenheit (15 to 60
degrees C), with the potential for liquid water. "That's not bad," he said.

       The outermost planet is at least four times as massive as Jupiter 
and completes one orbit every 3.5 to four years, at an average distance 
of about 250 million miles. The temperature there could be a chilly 112 
degrees below zero (minus 80 degrees C), Beichman said.


       Planetary scientists once thought such giant planets had to form
relatively far out from their parent star, but the researchers said these
three giants must have either formed closer in or migrated toward the
center in a game of planetary billiards.


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