From: Ron Baalke [EMAIL PROTECTED]
Subject: NASA Researcher Validates Discovery of Planets' Gravitational 'Dance'
To: [EMAIL PROTECTED] (Astronomy List)
Date: Tue, 9 Jan 2001 13:46:37 -0800 (PST)
X-Mailer: ELM [version 2.5 PL1]
Kathleen Burton
Ames Research Center, Moffett Field, CA
(Phone: 650/604-1731 or 650/604-9000)
[EMAIL PROTECTED]
News Release: 01-02AR
NASA Researcher Validates Discovery of Planets' Gravitational "Dance"
January 9, 2001
A team of planet hunters today announced a discovery that will help
researchers better understand planet migration and how planets'
gravitational pulls influence each other. The discovery was announced
at the American Astronomical Society meeting in San Diego.
The planet sleuths from the University of California at Berkeley,
NASA and other institutions discovered the planetary pair locked in
what appears to be "resonant" orbits, moving in synch around the star
with orbital periods of 60 and 30 days. Because of the 2-to-1 ratio,
the inner planet goes around the star twice for each orbit of the
outer one. They gravitationally tug on each other to maintain this
synchronicity.
"The resonance between the two orbiting planets is among the most
exciting planet detection discoveries to date," said Dr. Jack
Lissauer, a NASA Ames Research Center scientist based in the heart of
California's Silicon Valley. A "resonance" is similar to the harmonic
vibration produced by plucking two notes on a stringed instrument.
This gravitational pas de deux between the two planets is common
among moons and asteroids, but not planets. The axes of the two newly
detected planets' elliptical orbits also appear to be nearly
perfectly aligned.
Lissauer and State University of New York at Stony Brook graduate
student Eugenio Rivera used a numerical model to demonstrate the
stability of the nearly twin orbits around the star known as Gliese
876, a dim red dwarf 15 light years from Earth in the constellation
Aquarius. "Questions about planetary migration and gravitational
influence are still very much unsolved," Lissauer said.
"This discovery is significant for several reasons," said Lissauer.
"This is the first extra-solar planetary system to show a strong
resonance. It also is the smallest star known to have any orbiting
planets, much less two," he said.
The two gravitationally linked planets have masses of at least 0.5
and 1.8 times the mass of Jupiter, he said. The inner planetary
companion was not recognized at first because the orbital resonance
allowed the pair of planets to masquerade as a single planet with an
elongated orbit.
The two orbiting planets are located relatively close to each other,
within 0.08 Astronomical Units (the distance between the Earth and
the sun) of each other, less than one-third the distance from the
Earth to its nearest neighbor, Venus.
In our solar system, the only known resonances between a pair of
planets is Pluto, which orbits the sun twice for every three times
Neptune circles the sun.
Besides Lissauer, the planet-hunting team that discovered the system
includes Drs. Geoff Marcy and Debra Fischer of the University of
California at Berkeley; Dr. Paul Butler of the Carnegie Institution
of Washington; and Dr. Steve Vogt of the University of California at
Santa Cruz.
Though significant and unusual, the discovery will require more
modeling before researchers can determine what the resonance they
discovered actually means.
The team based both sets of its conclusions on 6 years of precise
Doppler measurements and observations made at the Keck I telescope
atop Mauna Kea in Hawaii and the Lick Observatory telescope in
California. The research is part of a multi-year project to look for
planets among 1,100 stars within 300 light years of Earth. The
project is supported by NASA, the National Science Foundation and Sun
Microsystems.
More information about these discoveries is available at
http://www.exoplanets.org
-end-
==
You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED]
Project information and list (un)subscribe info: http://klx.com/europa/