The space agency announced Thursday that its planet-hunting mission, Kepler, has discovered an exoplanet that is comparable to our own in age and size, orbiting a Sun-like star at a distance that makes it neither too hot nor too cold to support life.
Kepler 452b, as the planet is called, is the smallest known planet outside our solar system that is in the habitable zone of a G2-class star, like the Sun. It is about 6 billion years old, 60 percent larger than the Earth in diameter, and sits in the constellation Cygnus, about 1,400 light-years away from Earth.
Its discovery – 20 years after scientists first proved that stars other than our own host planets – marks a milestone in humankind’s 2,500-year-old quest for other worlds.
The new planet circles its Sun-like star in an orbit that lasts 385 days, placing it firmly in the zone that scientists consider habitable – where temperatures are warm enough for there to be liquid water on the surface.
“Today the Earth is a little less lonely, because there’s a new kid on the block,” Jon Jenkins, Kepler data analysis lead at NASA’s Ames Research Center in Moffett Field, Calif., said at a Thursday news conference announcing the discovery. “We believe … that this is the nearest thing that we’ve found to an Earth system analogue, a twin system to our own.”
John Grunsfeld, associate administrator of NASA’s Science Mission Directorate at the agency’s headquarters in Washington, called the new planet a “close cousin to the Earth.”