Team Finds it outside
earth's solar system
Discovery of a giant planet
BY STUART WOLPERT
UCLA Today
A European/American team of astronomers that includes a UCLA scientist
has discovered a giant planet, approximately five times the mass
of Jupiter, some 200 light years from Earth. In so doing, they have
produced the first image of a planet found outside our solar system.
The giant planet, located near the southern constellation of Hydra,
is gravitationally bound to a young brown dwarf. Both move together.
Brown dwarfs are failed stars about the size of Jupiter, with a
much larger mass — but not quite large enough to become stars.
Like the sun and Jupiter, they are composed mainly of hydrogen gas,
perhaps with swirling cloud belts. But unlike the sun, they emit
almost no visible light.
The planet was first sighted by the team a year ago in April as
a faint source of infrared emission. But it was impossible then
to determine that it was a planet. It could have been an unusual
galaxy or a peculiar cool star, although scientists thought this
unlikely because it was located so close to the young brown dwarf
in the plane of the sky.
The team, led by Gael Chauvin of the European Southern Observatory
(ESO), found that the infrared spectrum of the object they discovered,
now called 2M1207b, shows a strong signature of water molecules,
indicating that the object is cold. Based on the infrared colors
and spectral data, evolutionary model calculations by team members
led them to believe that 2M1207b was a planet five times the mass
of Jupiter.
That finding was confirmed in February and March when the astronomers
took new images of the brown dwarf and its companion planet using
the Very Large Telescope (VLT) operated by ESO, an international
astronomical organization.
Located on a mountain in the Chilean Andes, the VLT is one of the
world’s most advanced optical and infrared telescopes, capable
of producing extremely sharp images and recording light from the
faintest and most remote objects in the universe.
“Our new images show convincingly that this really is a planet,
the first planet that has ever been imaged outside of our solar
system,” Chauvin said. The paper describing their research
has been accepted for publication in Astronomy and Astrophysics,
a premier journal in astronomy.
Said Ben Zuckerman, UCLA professor of physics and astronomy and
a team member: “The two objects — the giant planet and
the young brown dwarf — are moving together; we have observed
them for a year, and the new images essentially confirm our 2004
finding.”
Zuckerman said he is “more than 99% confident” that
it is a planet. “This is also the first time that a planet
outside of our solar system has been detected far from a star or
brown dwarf — nearly twice as far as the distance between
Neptune and the Sun.”
Anne-Marie Lagrange, another member of the team from the Grenoble
Observatory in France, said, “Our discovery represents a first
step towards one of the most important goals of modern astrophysics:
to characterize the physical structure and chemical composition
of giant and, eventually, terrestrial-like planets.”
The giant planet most likely did not form as did the planets in
our solar system, Chauvin said.
“Instead, it must have formed the same way our Sun formed,
by a one-step gravitational collapse of a cloud of gas and dust,”
he said.
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