WASHINGTON – A team of astronomers has found a Jupiter-sized planet orbiting a faint nearby star similar to our Sun, raising
intriguing prospects of finding a solar system like our own.
The planet is the second found orbiting 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 we 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 periods, planetary systems
that look more like our Solar System.”
The planet-search team, which is supported by NASA and the
National Science Foundation, Arlington, VA, has been
instrumental in finding a majority of the planets outside our
Solar System (also called 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, Mountain
View, CA. Their report on the new planet has been submitted
to the Astrophysical Journal.
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. Using telescopes at the University of
California’s Lick Observatory, they measure changes in the
characteristics of light emitted by the stars. Those changes,
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.
The star is a yellow star similar to the sun, probably about
seven billion years old and located about 51 light-years from
Earth. A light-year, the distance light travels in one year,
is approximately 6 trillion miles.
“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.”
