Scientists on the hunt for extraterrestrial life have discovered “the closest twin to Earth” outside the solar system, NASA announced on 23 July 2015. Working off four years’ worth of data from the Kepler space telescope, researchers from NASA, the Seti Institute and several universities announced the new exoplanet along with 12 possible “habitable” other exoplanets and 500 new candidates in total. The new planet, named Kepler 452b, is “the closest twin to Earth that we’ve found so far in the dataset”, said John Grunsfeld, associate administrator for Nasa’s mission directorate.
The planet is like Earth’s “older, bigger first cousin.” The research suggests 452b has five times the mass of Earth, is about 1.5bn years older, and has a gravity about twice as powerful as our own. About 1,400 light years away, Kepler 452b orbits a star similar to our Sun, and at about the same distances as Earth orbits the Sun, meaning it has a similar length year and exists in the “habitable zone” where liquid water can exist on a planet. They suspect the planet is rocky, likely with active volcanoes, and has a thicker atmosphere with greater cloud cover than the Earth. The new planet receives 10% more energy than the Earth, meaning it could provide a glimpse into a burning, waterless future on Earth. “Kepler 452b could be experiencing now what the Earth will undergo more than a billion years from now,” said Doug Caldwell, a Seti Institute scientist on the Keplar mission. “If Kepler 452b is indeed a rocky planet,” he said, its location “could mean that it is just entering a runaway greenhouse phase of its climate history. Its ageing sun might be heating the surface and evaporating any oceans. The water vapor would be lost from the planet forever.”
“We’re trying to answer really fundamental questions,” Grunsfeld said. “Where are we going as human beings, and of course the really grand question: are we alone in the universe?” Of the 4,661 exoplanet candidates catalogued by the Kepler mission, 1,028 have been confirmed. Eleven of those are confirmed exoplanets less than twice Earth’s size and in the habitable zone of their stars. The first exoplanet orbiting a distant star was discovered in 1995. The Kepler space telescope identifies possible planets by observing periodic dips in the brightness of stars as planets pass before them, in the same way the moon causes an eclipse on Earth. However, confirmation of their true planetary status requires observations by other instruments, typically looking for slight shifts in the motion of the host suns.
Alan Yuhas for The Guardian
23 July 2015