Astronomers Discover First Rocky Exoplanet

Astronomers announced today the possible discovery of a rocky planet only twice as wide and seven and a half times as massive as the Earth orbiting a small red dwarf star about 15 light years away. Paul Butler from the Carnegie Institute of Washington, Geoffrey Marcy from the University of California, Berkeley, Jack Lissauer of NASA/Ames Research Center, and Eugenio J. Rivera of the University of California Observatories/Lick Observatory at UC Santa Cruz provided details about the discovery in a press conference held today at the National Science Foundation in Arlington, Virginia. Any similarity with the Earth ends with its size and mass. Conditions on the planet are probably hot (approximately 200 to 400 degrees Celsius) because it orbits only 2 million miles from its parent star, Gliese 876. That is much closer than Mercury orbits our own Sun. Because of the planet’s size and closeness to its parent star, it is not likely a gas giant but instead a rocky world similar to the composition of the terrestrial planets in our own solar system.

Two other planets have previously been discovered in the system, including a gas giant twice as large and another half as large as Jupiter. The planets were discovered by carefully measuring the wobble of the parent star and determining what other gravitational bodies must be present in the system to create that wobble. No direct images have been taken. Technology to be developed over the next decade or longer could eventually lead to snapshots of exoplanets as small as the Earth.

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