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Posted by baalke on November 6, 2007, 4:16 pm
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Nov. 6, 2007
Grey Hautaluoma
Headquarters, Washington
202-358-0668
grey.hautaluoma-1@nasa.gov
DC Agle
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-9011
agle@jpl.nasa.gov
Denize Springer
San Francisco State University, Calif.
415-405-3803
denize@sfsu.edu
Bob Sanders
University of California, Berkeley
510-643-6998
rsanders@berkeley.edu
RELEASE: 07-248
SCIENTISTS DISCOVER RECORD FIFTH PLANET ORBITING NEARBY STAR
WASHINGTON - Astronomers have announced the discovery of a fifth
planet circling 55 Cancri, a star beyond our solar system. The star
now holds the record for number of confirmed extrasolar planets
orbiting around it in a planetary system.
55 Cancri is located 41 light-years away in the constellation Cancer
and has nearly the same mass and age as our sun. It is easily visible
with binoculars. Researchers discovered the fifth planet using the
Doppler technique, in which a planet's gravitational tug is detected
by the wobble it produces in the parent star. NASA and the National
Science Foundation funded the research.
"It is amazing to see our ability to detect extra-solar planets
growing," said Alan Stern, associate administrator for the Science
Mission Directorate at NASA Headquarters, Washington. "We are finding
solar systems with a richness of planets and a variety of planetary
types comparable to our own."
The newly discovered planet weighs about 45 times the mass of Earth
and may be similar to Saturn in its composition and appearance. The
planet is the fourth from 55 Cancri and completes one orbit every 260
days. Its location places the planet in the "habitable zone," a band
around the star where the temperature would permit liquid water to
pool on solid surfaces. The distance from its star is approximately
72.5 million miles, slightly closer than Earth to our sun, but it
orbits a star that is slightly fainter.
"The gas-giant planets in our solar system all have large moons,"
said
Debra Fischer, an astronomer at San Francisco State University and
lead author of a paper that will appear in a future issue of the
Astrophysical Journal. "If there is a moon orbiting this new, massive
planet, it might have pools of liquid water on a rocky surface."
Fischer, University of California, Berkeley, astronomer Geoff Marcy
and a team of collaborators discovered this planet after careful
observation of 2,000 nearby stars with the Shane telescope at Lick
Observatory located on Mt. Hamilton, east of San Jose, Calif., and
the W.M. Keck Observatory on Mauna Kea, Hawaii. More than 320
velocity measurements were required to disentangle signals from each
of the planets.
"This is the first quintuple-planet system," Fischer said. "This
system has a dominant gas giant planet in an orbit similar to our
Jupiter. Like the planets orbiting our sun, most of these planets
reside in nearly circular orbits."
"Discovering these five planets took us 18 years of continuous
observations at Lick Observatory, starting before any extrasolar
planets were known anywhere in the universe," said Marcy, who
contributed to the paper. "But finding five extrasolar planets
orbiting a star is only one small step. Earth-like planets are the
next destination."
The planets around 55 Cancri are somewhat different from those
orbiting our sun. The innermost planet is believed to be about the
size of Neptune and whips around the star in less than three days at
a distance from the star of approximately 3.5 million miles. The
second planet is a little smaller than Jupiter and completes one
orbit every 14.7 days at a distance from the star of approximately
11.2 million miles. The third planet, similar in mass to Saturn,
completes one orbit every 44 days at a distance from the star of
approximately 22.3 million miles. The newly discovered planet is the
fourth planet. The fifth and most distant known planet is four times
the mass of Jupiter and completes one orbit every 14 years at a
distance from the star of approximately 539.1 million miles. It is
still the only known Jupiter-like gas giant to reside as far away
from its star as our own Jupiter.
"This work marks an exciting next step in the search for worlds like
our own," said Michael Briley, an astronomer at the National Science
Foundation. "To go from the first detections of planets around
sun-like stars to finding a full-fledged solar system with a planet
in a habitable zone in just 12 years is an amazing accomplishment and
a testament to the years of hard work put in by these investigators."
For visuals depicting the new planets on the Web, visit:
http://www.nasa.gov/audience/formedia/telecon-20071106/index.html
For information about NASA and agency programs, visit:
http://www.nasa.gov
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