About 500 light years away in the constellation Cygnus, there exists a cool and dim class M type dwarf star, it is about half the size and mass of our Sun. In that star system, there are five planets rotating this small star, especially, one named Kepler-186f orbits the M dwarf star every 130 days from 53 million km – it is about the same distance as Sun to Mercury, but this M dwarf star is much smaller and cooler, therefor this planet Kepler-186f falls within ‘habitable zone’ where the water exists in liquid form.
The planet was discovered by planet hunting spacecraft Kepler. The spacecraft uses transit technique to discover planets orbiting alien stars. When planet crosses the star, the light of the star is dimmed by slight amount and the Kepler spacecraft’s apparatus is accurate enough to detect that very tiny drop in the brightness therefore identifying the planet rotating the star. It is near impossible to directly detecting the planets light years away as they are not a direct light source and looks very dim comparing to stars.
Planet Kepler-186f is almost the size of our planet Earth, and this discovery confirms that earth sized planets exist in the star system other than our sun. Because of the detection method used by spacecraft Kepler, the mass and composition of the planet Kepler-186f is not known, but research suggest that it is probably a rocky planet.
Even though Kepler-186f orbits its star much closer than Earth to Sun, but on the surface of Kepler-186f, brightness of the star at noon time looks like only as bright as our sun appears to us about an hour before sunset – the reason is Kepler-186f’s mother star is very dim and cooler than our sun.
With Kepler-186f, there are other 4 planets rotating the mother star but much closer than Kepler-186f. Kepler-185b orbits the star in every 4 days, Kepler-186c orbits in 7 days, Kepler-186d orbits in 13 days and finally Kepler-186e orbits in 22 days. All of these planets are much closer to the star and therefore much hotter to be in habitable zone.
In the future NASA will use Transit Exoplanet Survey Satellite and James Webb Space telescopes (it has 7 times more mirror space than current space telescope – Hubble ST) to identify earth like planets orbiting Sun like stars and also study the composition and chemical components of those planets.
Visiting any of these planets or even sending spacecraft for these planets are meaning less for now considering the vast distance and limitation of our technology.
Source: NASA
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