NASA Kepler spies Earth-sized planet in habitable zone

Kepler sighting is more reminiscent of Earth than other previously spotted planets

nasa artist impression
NASA today said its planet hunting Kepler Space Telescope has spotted what the agency called the first Earth-size planet orbiting a star in the "habitable zone" -- the range of distance from a star where liquid water might pool on the surface of an orbiting planet.

NASA said that the  discovery of what will be called Kepler-186f confirms that planets the size of Earth exist in the habitable zone of stars other than our sun. While planets have previously been found in the habitable zone, they are all at least 40% larger in size than Earth and understanding their makeup is challenging. Kepler-186f is more reminiscent of Earth.  Although the size of Kepler-186f is known, its mass and composition are not. Previous research, however, suggests that a planet the size of Kepler-186f is likely to be rocky, NASA said.

+More on Network World: NASA: Kepler's most excellent space discoveries+

Kepler-186f is some 500 light-years from Earth in the constellation Cygnus. The system is also home to four companion planets, which orbit a star half the size and mass of our sun. The star is classified as an M dwarf, or red dwarf, a class of stars that makes up 70% of the stars in the Milky Way galaxy, NASA stated.

Some other facts on the discovery:

  • Kepler-186f orbits its star once every 130-days and receives one-third the energy from its star that Earth gets from the sun, placing it nearer the outer edge of the habitable zone.
  • On the surface of Kepler-186f, the brightness of its star at high noon is only as bright as our sun appears to us about an hour before sunset.
  • The four companion planets, Kepler-186b, Kepler-186c, Kepler-186d, and Kepler-186e, whiz around their sun every four, seven, 13, and 22 days, respectively, making them too hot for life as we know it. These four inner planets all measure less than 1.5 times the size of Earth.
  • M dwarfs are the most numerous stars. The first signs of other life in the galaxy may well come from planets orbiting an M dwarf, NASA said

"When we search for life outside our solar system we focus on finding planets with characteristics that mimic that of Earth," said Elisa Quintana, research scientist at the SETI Institute at NASA's Ames Research Center in Moffett Field, Calif., and lead author of the paper published on the current discovery in the journal Science. "Finding a habitable zone planet comparable to Earth in size is a major step forward."

The discovery is also a testament to how much data Kepler has produced and how much of an impact its findings will continue to influence the astronomy community even though it currently isn't capable of doing anything.

You may recall that since last May the telescope has been largely disabled.  There is a plan afoot known as Kepler Second Light or K2 that would make use of the Sun and Kepler's orbit around  it to stabilize the craft and let it start taking images of space again.

Kepler's mission was to determine what percentage of stars like the sun harbor small planets the approximate size and temperature of Earth. For four years, the space telescope simultaneously and continuously monitored the brightness of more than 150,000 stars, recording a measurement every 30 minutes. More than a year of the collected data remains to be fully reviewed and analyzed, NASA has said.

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