How Do Planets Form?

Mercury, November/December 2000 Table of Contents

Astronomers are looking for clues from our solar system and others to determine whether planets form easy and fast or hard and slow.

by David A. Weintraub, Vanderbilt University

"The recent discovery of at least 50 extrasolar giant planets is one of the most profound and exciting events in modern science. But those of us who are curious about the commonality of extraterrestrial life are more interested in knowing about Earth-like planets, which are much harder to detect. So we should ask, what exactly do we now know about small extrasolar planets?"

The answer to this question is, unfortunately, "very little." Right now, the technology simply doesn't exist to study Earth-sized planets orbiting other stars. Being an impatient lot, astronomers don't want to wait for a decade or more until the technology becomes available. Some of these astronomers, including the author, are focusing their attention on understanding how planets form, which can give insight to the diversity of planets that might be out there.

David Weintraub outlines the latest theories of planet formation. He discusses what the solar system's architecture implies for planet formation theory in general. But he also discusses the 50 or more extrasolar planets that have been found, and what they appear to be telling astronomers. Even though extrasolar planets are being found in abundance, the news isn't necessarily rosy for those who want to believe in extraterrestrial intelligent life.

Painting courtesy of Lynette Cook
www.spaceart.org/lcook/space.html

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