Don Savage
Headquarters, Washington, DC May 28, 1998
(Phone: 202/358-1547)
Bill Steigerwald
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-5017)
Ray Villard
Space Telescope Science Institute, Baltimore, MD
(Phone: 410/338-4514)
RELEASE: 98-91
HUBBLE TAKES FIRST IMAGE OF A POSSIBLE PLANET
AROUND ANOTHER STAR AND FINDS A RUNAWAY WORLD
NASA's Hubble Space Telescope has given astronomers their
first direct look at what is possibly a planet outside our solar
system -- one apparently that has been ejected into deep space by
its parent stars.
The discovery, made by Susan Terebey of the Extrasolar
Research Corporation in Pasadena, CA, and her team using Hubble's
Near Infrared Camera and Multi-Object Spectrometer (NICMOS),
further challenges conventional theories about the birth and
evolution of planets, and offers new insights into the formation
of our own Solar System.
Located in the sky within a star-forming region in the
constellation Taurus, the object, called TMR-1C, appears to lie at
the end of a strange filament of light that suggests it has
apparently been flung away from the vicinity of a newly forming
pair of binary stars.
At a distance of 450 light-years, the same distance as the
newly formed stars, the candidate protoplanet would be ten
thousand times less luminous than the Sun. If the object is a few
hundred thousand years old, the same age as the newly formed star
system which appears to have ejected it, then it is estimated to
be 2-3 times the mass of Jupiter, the largest gas giant planet in
our Solar System.
Also possible is that the object is up to ten million years
old, the same age as other young stars nearby, in which case it
may be a giant protoplanet or a brown dwarf star. A brown dwarf
star is a small star that has failed to sustain nuclear fusion.
The candidate protoplanet is now 130 billion miles from the
parent stars and predicted to be hurtling into interstellar space
at speeds up to 20,000 miles per hour (10 kilometers/sec) --
destined to forever drift among the Milky Way's starry population.
Hubble researchers estimate the odds at two percent that the
object is instead a chance background star.
"If the results are confirmed, this discovery could be
telling us gas giant planets are easy to build. It seems unlikely
for us to happen to catch one flung out by the stars unless gas
giant planets are common in young binary systems," said Terebey.
"The results don't directly tell us about the presence of any
terrestrial planets, like Earth," she adds. "However, we believe
gas giants do influence the formation of much smaller rocky
planets."
Current models predict that very young giant planets are
still warm from gravitational contraction and formation processes.
This makes them relatively bright in infrared light compared to
old giant planets such as Jupiter. Even so, young planets are
difficult to find in new solar systems because the glare of the
central star drowns out their feeble glow. Young planets ejected
from binary systems would therefore represent a unique opportunity
to study extrasolar planets with current astronomical technology.
The discovery also challenges conventional theories that
predict gas giant planets take millions of years to coagulate from
dust in space. Instead, it favors more recent ideas that large,
low-density planets may condense out of gas very quickly, at the
same time their parent star does.
"This observation pushes back the clock on planet formation
and offers short time scales which allow us to see how things
form. This provides valuable new clues to the origin of our Solar
System," says Terebey.
The candidate protoplanet was accidentally discovered by
Terebey and colleagues while studying Hubble infrared images of
newly formed protostars in a molecular cloud in Taurus. The
exquisite sensitivity and sharpness of NICMOS clearly revealed the
object's pinpoint image. However, it might have been dismissed as
a background star if not for the presence of a bizarre 130-
billion-mile-long filamentary structure that bridges the space
between the binary pair and the candidate protoplanet.
"I said to myself, 'This is really weird, what in the world
could it be?'" recalls Terebey. She speculates it could be a
tunnel the runaway object burrowed through a dust cloud
surrounding the stars. This created a "light tube" which channels
light from the stars deep inside their dusty cocoon - like a light
beam traveling through a length of fiber optic cable.
This brought Terebey to the tantalizing possibility that the
planet had been flung into deep space by a gravitational
"slingshot" effect from its parent stars. This could have
happened if the planet's orbit allowed it to rob momentum from the
stars and pick up so much speed that it escaped the system,
similar to the way spacecraft perform gravitational "slingshot"
maneuvers to pick up speed by flying close by a planet.
"We know that many triple star systems eventually toss out
the lowest mass star. And we can predict the speed at which the
object should be moving, based on the separation of the binary
stars," said Terebey.
Future observations call for images taken at a later date, to
confirm the object's predicted movement across the sky. In
addition, the spectrum of the object will tell whether the object
is a background star, brown dwarf, or something whose spectrum is
less easy to predict, such as a giant protoplanet.
"We will just have to wait and see if future observations
confirm this picture," said Terebey. "However it turns out, we
have come to appreciate that protoplanet ejection by young binary
stars ought to happen, and it offers a new way to search for giant
planets."
"These future observations will be critical in verifying that
this object is truly a planet and not a brown dwarf," said Dr. Ed
Weiler, Director of the Origins Program at NASA Headquarters,
Washington, DC. "We are sharing this preliminary data with the
public at a very early stage in the research process because of
its potential importance and because of the compelling nature of
the image. If the planet interpretation stands up to the careful
scrutiny of future observations, it could turn out to be the most
important discovery by Hubble in its 8 year history".
The members of the research team include Susan Terebey
(Extrasolar Research Corp.), Dave Van Buren, Deborah L. Padgett,
Jet Propulsion Lab, Pasadena, CA (JPL), Terry Hancock (Extrasolar
Research Corp.), and Michael Brundage, JPL.
The Space Telescope Science Institute is operated by the
Association of Universities for Research in Astronomy, Inc. (AURA)
for NASA, under contract with the Goddard Space Flight Center,
Greenbelt, MD. The Hubble Space Telescope is a project of
international cooperation between NASA and the European Space
Agency (ESA).
- end -
NOTE TO EDITORS: Images to accompany this release are available
to news media representatives by calling the Headquarters Imaging
Branch on 202/358-1900.
NASA photo number: Color: 98-HC-191
Images and information about this discovery can also be found on
the Internet at: http://oposite.stsci.edu/1998/19
(
geocities.com/heartland/plains) (
geocities.com/heartland)