In search of a second Earth

Kepler mission was launched in 2009 and January this year, the telescope has discovered 1013 confirmed exoplanets (all planets orbit a star that is not our Sun, compact star or brown dwarf called exoplanets – note. Ed.), Which are located in 440 star systems, and more unconfirmed nearly 3,200 other objects that may be exoplanets. In order for any of them to be declared under conditions close to Earth, it must meet several criteria. The first is circling a star similar to our sun. This will have similar characteristics of gravitational attraction and levels of solar radiation to provide the necessary conditions for life. The second important criterion is the planet is in the habitable zone. This is the area around a star where conditions are most favorable for life. Habitable zone depends mainly on the temperature of the sun, color and others. Therefore, this area usually varies stars. If it is too close to the sun, the planet’s surface would be too hot to be able to form life, and it will be more like an analogue of Mercury than on Earth. If you too remote, most likely it will be paralyzed in the eternal ice. The third factor are the very qualities of the planet. The size and its mass should not differ too much from the earth, and the time for which orbits its star. The task before Kepler is to find planets precisely to meet these requirements.

The first contenders

In December 2011, Kepler mission discovered the first exoplanet, which is located in the habitable zone – Kepler-20e. However, it is smaller than Earth and orbits its sun in just six days. The star itself is smaller and cooler than our sun. But because of a number of factors Kepler-20e proved a much hotter surface and low gravity, which can not hold any atmosphere or water. In the same month of 2011, scientists from NASA announced a second candidate – Kepler-20b. This is the first planet that was discovered in the habitable zone of a star very similar to our sun. The downside is that the planet itself is twice the size of Earth and probably not a hard surface. In 2014, scientists discovered the first planet with approximate parameters of the Earth, which is located in the habitable zone. It is called Kepler-186f, but goes doubly little star – a red dwarf class M.