Inching ahead on their quest for what they call Earth 2.0, astronomers from NASA’s Kepler planet-hunting spacecraft announced on Thursday that they had found what might be one of the closest analogues to our own world yet.
Named Kepler-452b, the planet is the smallest world discovered orbiting in the habitable zone of a star.
What makes this world remarkable is that it orbits its star at about the same distance that Earth orbits the sun. What’s more, its home star looks to be similar to our sun.
. The planet takes 385 days to orbit its star. It is older and bigger than Earth, but lies within the conservative habitable zone of its parent star.
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. 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.
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.
The new planet’s size puts it right on the edge between being rocky like Earth and being a fluffy gas ball like Neptune, according to studies of other such exoplanets. In an email, Jon Jenkins of NASA’s Ames Research Center, home of the Kepler project, and lead author of a paper being published in The Astronomical Journal, said the likelihood of the planet’s being rocky was 50 percent to 62 percent, depending on uncertainties in the size of its home star. That would mean its mass is about five times that of Earth.
Future Nasa missions, like the Transiting Exoplanet Survey Satellite and the James Webb Space Telescope, will discover the nearest rocky exoplanets and determine their composition and atmospheric conditions, continuing humankind’s quest to find truly Earth-like worlds.’
In 2017 Nasa plans to launch the successor to the Kepler mission, that will search the nearest solar systems for exoplanets.
Grunsfeld said that with better telescopes and satellites, scientists may one day be able to ‘make the first primitive maps of an Earth-like planet’, including details of ‘whether they have oceans, clouds, perhaps even seasons’.