Astronomers using a Jet Propulsion Laboratorydeveloped Kepler Space Telescope have discovered the first planet that is about the same size of Earth and orbits a star within the "habitable" zone, NASAofficials announced Thursday.
"The discovery of Kepler-186f is a significant step toward finding worlds like our planet Earth," according to Paul Hertz, director of NASA's Astrophysics Division.
According to NASA, other planets have been found in the "habitable" zone of stars, but they were all at least 40 percent larger than Earth.
Kepler-186f is about 500 light years from Earth in the constellation Cygnus. NASA officials said a planet is considered in the "habitable zone" if its distance from a star could allow the pooling of water on its surface.
NASA officials noted that the planet is on the "outer edge" of the habitable zone. It orbits its star in 130 days, and the brightness of its sun at high noon is roughly as bright as our sun appears an hour before sunset, according to NASA.
"Being in the habitable zone does not mean we know this planet is habitable," said Thomas Barclay, research scientist at the Bay Area Environmental Research Institute at NASA's Ames Research Center in Moffett Field. "The temperature on the planet is strongly dependent on what kind of atmosphere the planet has.
"Kepler-186f can be thought of as an Earth-cousin rather than an Earth- twin," he said. "It has many properties that resemble Earth."
NASA astronomers continue to search for Earth-twins, which are Earth- sized planets orbiting within the habitable zone, and measure their chemical makeup.
—City News Service