Scientists discover record fifth planet orbiting nearby star
7/11/2007 17:41
Astronomers announced in Washington yesterday that they have discovered 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. 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 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.
"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."
"But finding five extrasolar planets
orbiting a star is only one small step. Earth-like planets are the next
destination," said Geoff Marcy, who contributed to the paper.
|
