NSF PR 01-64 - August 15, 2001
Donald Savage, NASA
Vernon Pankonin, NSF
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Jupiter-Size Planet Found Orbiting Star in Big
A team of astronomers has found a Jupiter-size planet
in a circular orbit around a faint nearby star, raising
intriguing prospects of finding a solar system with
characteristics similar to our own.
The planet is the second found to orbit the star 47
Ursae Majoris in the Big Dipper, also known as Ursa
Major or the Big Bear. The new planet is at least
three-fourths the mass of Jupiter and orbits the star
at a distance that, in our solar system, would place
it beyond Mars but within the orbit of Jupiter.
"Astronomers have detected evidence of more than 70
extrasolar planets," said Morris Aizenman, a senior
science advisor at the National Science Foundation
(NSF). "Each discovery brings us closer to determining
whether other planetary systems have features like
those of our own."
"For the first time we have detected two planets in
nearly circular orbits around the same star," said
team member Debra Fischer of the University of California
at Berkeley. "Most of the 70 planets people have found
to date are in bizarre solar systems, with short periods
and eccentric orbits close to the star. As our sensitivity
improves we are finally seeing planets with longer
orbital period, planetary systems that look more like
our solar system."
The planet-search team, which is supported by NSF and
NASA, has been instrumental in finding a majority
of the extrasolar planets. Besides Fischer, the team
includes Geoffrey Marcy, also of Berkeley; Paul Butler
of the Carnegie Institution of Washington; Steve Vogt
of the University of California at Santa Cruz; and
Gregory Laughlin of NASA's Ames Research Center. Their
report on the new planet has been submitted to Astrophysical
A few years ago, Marcy and Butler discovered a planet
more than twice the mass of Jupiter in a circular
orbit around the same star. The star is one of 100
that the scientists have targeted since 1987 in their
search for evidence of extrasolar planets. They use
the 3-meter and 0.6-meter telescopes at the University
of California's Lick Observatory to measure Doppler-shifted
light reaching the earth from stars. Regular changes
in the Doppler shift, they believe, signal the presence
of a planet periodically pulling the star toward or
away from Earth.
Fischer was able to see the periodic wobble from the
second planet, smaller and farther from the star than
the first, because of improved instrumentation that
can measure motions as small as three meters per second.
The star is a yellow star similar to the sun, probably
about seven billion years old and located about 51
light years from Earth.
"Every new planetary system reveals some new quirk
that we didn't expect. We've found planets in small
orbits and wacky eccentric orbits," said Marcy. "With
47 Ursae Majoris, it's heartwarming to find a planetary
system that finally reminds us of our solar system."
For a list of extrasolar planets, see: www.exoplanets.org
For illustrations, see: http://www.nsf.gov/od/lpa/news/press/01/newplanet.htm