Kepler Finds Earth-Sized Planets
Dec. 21, 2011
The Kepler space telescope has spotted two Earth-sized planets orbiting a star about 1,000 light-years from Earth. The two planets are the smallest yet found orbiting a sun-like star. The smaller of the planets, named Kepler-20e, is about 0.87 times as large as Earth–about the size of Venus. Kepler-20e is the first extrasolar planet smaller than Earth to be discovered. The other, named Kepler-20f, is 1.03 times as large as Earth–slightly larger than Earth. Astronomers believe that the two planets orbit too close to the star to support life. The surface temperatures were reported to be about 800 °F (426 °C) on Kepler-20f and about 1,400 °F (760 °C) on Kepler-20e.
Kepler-20e is the first planet smaller than Earth to be discovered outside the solar system. It orbits its star in only six days. NASA/Ames/JPL-Caltech
The Kepler telescope was launched in March 2009. Its main mission is to search one section of our galaxy for Earth-like planets in the “habitable zone.” The habitable zone, also called the Goldilocks zone, is the region around a star that scientists believe is neither too hot nor too cold to support life as we know it. In this zone, the temperature is cool enough to let liquid water form and warm enough to prevent water from freezing. Earth orbits in the habitable zone of the solar system. Kepler has searched over 150,000 stars for signs of orbiting planets. Earlier in December, the Kepler team announced the discovery of the first confirmed Earth-like planet in the habitable zone of another star. Scientists believe this planet is too large to have a solid rocky surface.
Although the three planets may not support life, the discoveries mark important steps in Kepler’s mission. Kepler’s ultimate goal is to spot a planet of similar size and temperature as Earth. At that point, scientists can study the planet with other instruments and techniques to determine if the planet does indeed have liquid water and, possibly, indications of life.
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