A large team of astronomers has announced the discovery of an Earth-sized exoplanet orbiting within the habitable zone of Kepler-186.
Artistic concept shows Kepler-186f. Image credit: NASA Ames
Kepler-186 is a M1-type dwarf star located in the constellation Cygnus, about 500 light years away from Earth.
The star hosts at least five planets, four of which – Kepler-186b, Kepler-186c, Kepler-186d, and Kepler-186e – are in very short-period orbits and are very hot, while the fifth, named Kepler-186f, is in the center of the habitable zone.
Kepler-186f was discovered by the transit method, which detects potential planets as their orbits cross in front of their star and cause a very tiny but periodic dimming of the star’s brightness.
After the team was able to confirm that Kepler-186f was a planet, they used the transit information to calculate the planet’s size.
Kepler-186f is about 1.1 times the radius of the Earth and orbits the star once every 130-days. The astronomers estimate that the planet receives about 1/3 the heat energy that our planet does from the Sun.
This is an artist’s impression showing the forested surface of Kepler-186f.
“What makes this finding particularly compelling is that this Earth-sized planet, one of five orbiting this star, which is cooler than the Sun, resides in a temperate region where water could exist in liquid form,” said Dr Elisa Quintana of the SETI Institute and NASA Ames Research Center, the lead author of the paper published in the journal Science.
Source: Elisa V. Quintana et al. 2014. An Earth-Sized Planet in the Habitable Zone of a Cool Star. Science, vol. 344, no. 6181, pp. 277-280; doi: 10.1126/science.1249403