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* Space Science Division, MS 245-3, National Aeronautics and Space
Administration, Ames Research Center, Moffett Field, CA 94035;
The first known extrasolar planet in orbit around a Sun-like star
was discovered in 1995. This object, as well as over two dozen
subsequently detected extrasolar planets, were all identified by
observing periodic variations of the Doppler shift of light emitted by
the stars to which they are bound. All of these extrasolar planets are
more massive than Saturn is, and most are more massive than Jupiter.
All orbit closer to their stars than do the giant planets in our Solar
System, and most of those that do not orbit closer to their star than
Mercury is to the Sun travel on highly elliptical paths. Prevailing
theories of star and planet formation, which are based on observations
of the Solar System and of young stars and their environments, predict
that planets should form in orbit about most single stars. However,
these models require some modifications to explain the properties of
the observed extrasolar planetary systems.
From the Academy
Japanese-american Frontiers Of Science Symposium
Extrasolar planets
,
, and Astronomy Department, University of California,
Berkeley, CA 94709; and § Department of Earth and Planetary
Sciences, Tokyo Institute of Technology, Ookayama, Megro-ku, Tokyo
152, Japan
To whom reprint requests should be addressed. E-mail:
lissauer{at}ringside.arc.nasa.gov.
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