Hubble
Sees Possible Extrasolar Planet
Published: 1998 May 28
1:04 pm ET (1704 UT)
Astronomers using the Hubble Space
Telescope have found what may be an extrasolar planet
-- the first seen directly -- that has been ejected
from its parent stars.
The
object, named TMR-1C, was seen in an infrared image of
a star-forming region in the constellation Taurus some
450 light-years from the Earth. The image shows the
object with a tendril of light stretching back to a
binary star system 210 billion km (130 million mi.)
away.
"If the results are confirmed,
this discovery could be telling us gas giant planets
are easy to build," said astronomer Susan Terebey
of the Extrasolar Research Corporation (ERC) of
Pasadena, California. "It seems unlikely for us
to happen to catch one flung out by the stars unless
gas giant planers are common in young binary
systems."
Terebey and a team of astronomers
from ERC and the Jet Propulsion Lab made the discovery
in an image taken by Hubble's NICMOS infrared camera
and spectrograph.
"This is incredibly exciting,
seeing a possible extrasolar planet for the first
time," said Alan Boss, an astrophysicist at the
Carnegie Institution of Washington. "This is a
major, unprecedented observation. It is as important
as the first indirect observation of an extrasolar
planet."
The size of the planet is dependent
on its age. If the body is very young -- a few hundred
thousand years old -- it should be no larger than a
few times the mass of Jupiter. However, if it is much
older -- up to ten million years old -- the body would
be much heavier, and more likely a brown dwarf or
giant protoplanet.
If it is young, then then planet
challenges current theories of planetary system
formation which require millions of years for planets
to form. "This observation pushes back the clock
on planet formation and offers short time scales which
allow us to see how things form," Terebey said.
"If this is a planet and the
system is about 300,000 years old, then the slower,
conventional theory doesn't fit," Boss said.
The object might have been dismissed
as a background star had it not been for the strange
filament of light stretching from the star to the
object. Terebey thinks it might be a
"tunnel" cut by the object through the
surrounding dust cloud, creating a path for light to
escape.
Astronomers still believe there is a
2 percent chance that the object is a background star
coincidentially located at the end of the tendril.
The object was likely ejected from
the binary star system in a gravitational slingshot
maneuver. "We know that many triple star systems
eventually toss out the lowest mass object,"
Terebey said. TMR-1C is moving away from its parent
stars at an estimated 10 km/sec (6 mi/sec).
Future observations are planned to
confirm the motion of the object and to take its
spectrum, in an effort to find if it is a planet,
brown dwarf, or protoplanet.
"These future observations will
be critical in verifying that the object is truly a
planet and not a brown dwarf," said Ed Weiler,
director of NASA's Origins program charged with
looking for extrasolar planets.
"If the planet interpretation
stands up to the careful scrutiny of future
observations," Weiler said, "it could turn
out to be the most important discovery by Hubble in
its 8-year history."
Related Stories:
Astronomers
Discover Planetary System Forming Around Star --
1998 April 21
A
Planet Around Beta Pictoris? -- 1998 January 15
Hubble
press release and images
Extrasolar
Research Corporation Web site
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