Jun 13 2005
From The Space Library
Scientists announced that they had found the most Earth-like planet ever before observed. Experts described the discovery as a milestone in efforts to find extraterrestrial life. Scientists led by Eugenio J. Rivera of the University of California, Santa Cruz, had discovered the planet, called GJ 876 d, orbiting the star GJ 876, which is 15 light-years from Earth. The planet, with a mass seven times that of Earth, is mostly composed of silicates, iron, and nickel~compositional matter more similar to that of Earth than the material of any other planet yet discovered. However, the planet is unlikely to support life, because estimated temperatures on the side of the planet facing the star are around 400° to 700°F~temperatures too hot for liquid water. Experts described the scientists' method of discovering the planet as a significant demonstration of the state-of-the art technologies for finding exoplanets~planets outside the solar system~that are as small as Earth. The scientists had used a spectrometer to discover GJ 876d, which is the smallest exoplanet yet found. Using the spectrometer had enabled them to observe changes in the exoplanet's reflected light. They had used the data to measure the planet's gravitational effects on the movements of its accompanying star. (John Johnson Jr., “Distant Object May Be a Planet Similar to Ours,” Los Angeles Times, 14 June 2005; Eugenio J. Rivera et al., “A ~7.5 Earth-Mass Planet Orbiting the Nearby Star, GJ 876,” Astrophysical Journal 634, no. 1 (20 November 2005): 625-640.)
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