Kepler-452b is an exoplanet orbiting the G-class star Kepler-452. It was identified by the Kepler space telescope and its discovery was publicly announced by NASA on 23 July 2015.[2] It is the first near-Earth-size planet discovered orbiting within the habitable zone of a star very similar to the Sun.[4] It is the second-most Earth-like exoplanet known to date, after Kepler-438b, although it is not known if Kepler-452b is rocky or a small gas planet.[5] However, based on its density, it is probably a rocky planet.
The star is 1,400 light-years away from the Solar System; at the speed of the New Horizons spacecraft, about 58,536 km/h (36,373 mph), it would take about 25.8 million years to get there.[6]
The planet takes 385 days to orbit its star.[7] It is older and bigger than Earth, but lies within the conservative habitable zone of its parent star.[8][9]
It has a probable mass five times that of Earth, and its surface gravity is twice Earth's, though calculations of mass for exoplanets are only rough estimates.[8] If it is a terrestrial planet, it is most likely a super-Earth with many active volcanoes due to its higher mass and density. The clouds on the planet would be thick and misty, covering much of the surface as viewed from space. Kepler-452 would look almost identical to the Sun as viewed from the surface.[10]
It is not clear if Kepler-452b offers habitable environments. It orbits a G2V-type star, like the Sun, with nearly the same temperature and mass. However, the star is six billion years old, making it 1.5 billion years older than the Sun. At this point in its star's evolution, Kepler-452b is receiving ten percent more energy from its parent star than Earth is currently receiving from the Sun. If Kepler-452b is a rocky planet, it would be subject to, or on the verge of, a runaway greenhouse effect.[11]