The Kepler-186 system is a stellar system, at least five planets, located 500 light-years from Earth in the constellation Cygnus. The five planets of Kepler-186 are orbiting a red dwarf star (spectral type M), a less massive star (0.48 solar mass) and less warm (3500 K, 5778 K for the Sun) the Sun, size and mass ≈ 0.5 relative to the Sun.
Red dwarfs are by far the most numerous stars in the universe, 70% of the stars in the Milky Way are red dwarfs and can shine for hundreds of billions of years. In April 2014, using the Kepler space telescope of NASA, a team of astronomers has discovered the first exoterre (size of the Earth) in the habitable zone of the star Kepler-186.
The discovery of the exoplanet Kepler-186F confirms that planets the size of Earth exist in the habitable zone of stars other than our Sun. This is not the first planet discovered in a habitable zone of a star, Dec. 6, 2011, NASA confirmed the discovery of Kepler-22b (2.4 R⊕) the first planet in the "habitable zone" its star. However, the exoplanet Kepler-186F has a size comparable to that of the Earth (1.11 R⊕) unfortunately we do not know its mass, depending on its composition (water, iron silicate).
« The discovery of Kepler-186F is an important step towards the search for worlds like our Earth planet », said Paul Hertz, director of the Astrophysics Division of NASA.
Will have to wait 2018, with the JWST telescope, to know the chemical composition of Kepler-186F and its possible atmosphere.
"When we look for life outside our solar system, we focus on the search for planets with characteristics similar to that of the Earth," said Elisa Quintana, researcher (SETI Institute / NASA Ames Research Center) and author main article published April 17, 2014 in the journal Science.
Kepler-186F which orbits its star in 130 days, is located near the outer edge of the habitable zone (see picture). This does not give us the average temperature of its surface, it depends on the atmosphere that we not yet know.
The four other planets of Kepler-186, Kepler-186b, Kepler-186c, Kepler-186d and Kepler-186e revolve around their sun, all respectively 4, 7, 13, and 22 days. So close to their star, they are certainly too hot to keep water in the liquid state. The 5 inner planets of this system are all smaller than 1.4 times the size of Earth. This major discovery is only the beginning of a long series of discoveries that all we will marvel as the Kepler space telescope simultaneously and continuously measure the brightness of over 150,000 stars.
NB: SETI Institute is a private nonprofit organization dedicated to scientific research, education and public awareness. The mission of the SETI Institute is to explore, understand and explain the origin, nature and prevalence of life in the universe.
star||≥ 30000 K|
|W||Wolf-Rayet star||≥ 25000 K|
star||10000 - 30000 K|
|A||large star||7300 - 10000 K|
|F||solar type||6000 - 7300 K|
|G||solar type||5300 - 6000 K|
|K||solar type||3800 - 5300 K|
|M||sub solar||2500 - 3800 K|
|C||carbon star||2400 - 3200 K|
|S||sub carbon star||2400 - 3500 K|
|L||hot brown dwarf||1300 - 2400 K|
|T||cool brown dwarf||600 - 1300 K|
|Y||sub brown dwarf||< 600 K|
NB: A transit occurs each time the planet passes between the star and the observer, at this moment, the planet obscures some of the light from the star, producing a detectable periodic dimming. Kepler requires at least three transits to verify a signal as that of a planet.
Image: Habitable zones of Kepler-186 (top) and the solar system (bottom). The image compares the planets of our inner solar system to Kepler-186, a stellar system, to five planet, located 500 light-years from Earth in the constellation Cygnus. The five planets of Kepler-186 are orbiting a red dwarf, a star of size and mass 1/2 relative to the Sun. Credit image: NASA Ames / SETI Institute / JPL-Caltech.
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