We orbit the Sun in our system’s “Goldilocks zone.” Earth is close enough to its star that water stays liquid but far enough away that it doesn’t boil. For life on Earth, it’s just right. The thinking is that since those conditions are just right for us, life could arise somewhere else in the void if it, too, in is a Goldilocks zone.
Today, NASA has announced that its Kepler spacecraft has found a possibly Earth-like planet in the Goldilocks zone of a star very similar to our sun. Dubbed Kepler-452b (orbiting the star Kepler-452), this discovery brings to total number of confirmed exoplanets to 1,030, and Earth twins to 1.
But Kepler-452b isn’t Earth’s identical twin. The planet is estimated to be at least 60% larger in diameter. And though the Kepler spacecraft is too far away from Kepler-452b to determine mass, composition, or atmosphere, NASA scientists say that previous research suggests its size means that it could be rocky like Earth.
Our planet-hunting spacecraft doesn’t look for planets directly; Kepler stared at a small patch of sky from 2009-2013, waiting for tiny dips in stars’ brightnesses. When a star briefly dims, the thinking is that something passed between the spacecraft and the star’s light, like you putting your hand up shield your eyes from the sun. In this case, a large planet would be your hand.
This “transit method” of exoplanet detection records those dips and infers the size of planets that made them. Since 2009, Kepler has been lucky to find a bounty of worlds beyond our system—planets have to pass in front of Kepler on roughly the same three-dimensional plane to be seen—and the candidate list is now up to 4,696.
Kepler got lucky again with 452b. It’s the smallest planet discovered in a habitable zone around a Sun-like star.
On Kepler 452b, you’d only have to wait a bit longer for your birthday: the planet is five percent further away from its sun than we are from ours, making a year span 385 days. However, its star is 1.5 billion years older than the Sun, 10 percent larger, and 20 percent brighter.
While 452b might be suitable for life, we won’t be visiting it any time soon—if ever. The planet orbits Kepler 452 over 1,400 light years away in the constellation Cygnus. Getting there would be like taking a roadtrip lasting the age of the universe. That extreme distance is a problem for Kepler, too. Earth’s possible twin isn’t close enough to determine its mass or atmosphere, meaning that it’s not close enough to find out if Earth really has a sister planet.
And just to be sure, the Search for Extra-Terrestrial Intelligence (SETI) Institute turned its telescopes towards the Kepler 452 system to see if six billion years in the habitable zone resulted in radio-emanating life like us. “No luck so far,” reports Nature.
IMAGES: NASA/JPL-Caltech/T. Pyle