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Published:April 25th, 2014 15:41 EST
News from NASA: First Earth-Sized Planet in Habitable Zone

News from NASA: First Earth-Sized Planet in Habitable Zone

By Derek Sanders

News from NASA: First Earth-Size Planet in Habitable Zone

On April 17th, astronomers using NASA`s Kepler Space Telescope have discovered the first Earth-sized planet orbiting the " habitable zone" of a star about 500 light-years from Earth in the constellation Cygnus. The habitable zone is the range of distance from a star where liquid water might pool on the surface of a planet in its orbit. This means that the planet, which has been given the designation Kepler-186f, proves that planets the size of Earth exist in the habitable zones of other stars.

The system is also home to four inner planets in orbit around a host star that is half the size and mass of Earth`s sun, all too hot to sustain life as we know it and all less than 1.5 times the size of Earth. Other planets found in this habitable zone but have all been significantly larger in size and scientists are unsure of their makeup. While the size of this new planet is known, being less than ten percent larger than Earth, its mass and composition are no, though previous research suggests that a planet of this size is likely to be rocky. Prior to this recent discovery, the most Earth-like planet on record was Kepler-62f, which is 40 percent larger than the Earth and orbits in its star`s habitable zone.

The star of the system is classified as a red dwarf, a class that makes up about 70 percent of stars in the Milky Way galaxy. Elisa Quintana, a research scientist at the SETI Institute at NASA`s Ames Research Center in Moffett Field, California, notes how numerous the stars, also known as M dwarfs are and says that the first signs of other life in the galaxy may well come from planets orbiting such a star.

"We know of just one planet where life exists -- Earth. When we search for life outside our solar system we focus on finding planets with characteristics that mimic that of Earth," said Quintana. "Finding a habitable zone planet comparable to Earth in size is a major step forward."

Scientists note that being in the habitable zone does not necessarily mean that the planet is habitable and while Kepler-186f does share some similarities with Earth, it also has its differences. Kepler-186f orbits its star once every 130 days and receives one-third of the energy from it that Earth gets from the sun, meaning it is near the outer edge of the habitable zone. On the planet`s surface the brightness of its star at noon is only as bright as Earth`s sun appears about an hour before sunset.

The next steps in looking for evidence of distant life include looking for planets that more closely resemble Earth. This means the planets need to be about Earth`s size, within the habitable zone of a sun-like star, and with similar chemical compositions. The best means that NASA has to achieve this goal is through use of the Kepler Space Telescope which can simultaneously and continuously measure the brightness of more than 150,000 stars and is capable of detecting Earth-sized planets around stars like the Sun. The Ames Research Center that Quintana works at is responsible for Kepler`s ground system development, mission operations and science data analysis.

Paul Hertz, NASA`s Astrophysics Division director at the agency`s headquarters in Washington, is positive about this discovery leading the way to more developments, mentioning future NASA projects that would assist their goal in finding more Earth-like planets. "The discovery of Kepler-186f is a significant step toward finding worlds like our planet Earth," Hertz said.

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