NASA's Kepler Mission Finds Earth's Distant Cousin

NASA's Kepler spacecraft has been quietly chugging along since 2009, looking for other planets that could potentially host life orbiting Sun-like stars. Today NASA announced that the space observatory has discovered a planet similar to Earth, only older and larger. 

Dubbed Kepler-452b, the newly discovered planet is one of 12 new small "habitable zone" candidate planets. That means they're located in a region not too close or too far from their star, and could potentially have liquid water pooling on the surface. Kepler-452b is the smallest planet of the bunch, but is still 60 percent bigger than Earth. Its mass and composition have yet to be determined, but it is expected to have a rocky terrain. 

Despite their size difference, Earth and Kepler-452b don't behave that differently. Earth orbits around the sun once every 365 days, while Kepler-452b orbits its parent star (Kepler-452) once every 385 days. The new planet's orbit is 5 percent longer, and it's located 5 percent farther away from its parent star.

Kepler-452 is about 20 percent brighter and 1.5 billion years older than the Sun, but they are roughly the same size. 

“We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth’s evolving environment," said Jon Jenkins, Kepler data analysis lead at NASA's Ames Research Center, who led the team that discovered Kepler-452b. "It’s awe inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That’s substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet.”

Kepler-452 and its planets are located in the constellation Cygnus, about 1400 light-years away. 

The discovery of Kepler-452b means there are now 1030 confirmed planets, according to NASA. There have been 4696 planet candidates detected by the Kepler mission, but they require follow-up observations to verify if they are actual planets. Twelve are pretty hefty, with diameters up to twice the size of Earth's, with orbits in their star's habitable zone. Nine orbit stars that are similar to our Sun in size and temperature. 

"This is really the first step, and humankind’s first step, to answering that question, 'Are we alone in the universe?'" said Jenkins in a NASA press conference. "You and I won’t be traveling to these planets, but our children’s children’s children may."