NASA astronomers believe they've found two new planets in the universe that resemble Earth, making these the best candidates for sustaining life outside of our own planet.
The new exoplanets, named Kepler 438b and Kepler 442b after the Kepler spacecraft that discovered them, look to be made up of a rocky terrain and are located in an area that has a habitable temperature zone and the possibility of water in a liquid state.
Of course, both planets are several hundreds of light years away and they orbit stars that are smaller than our own, so don't start your vacation plans just yet, but these two new planets join thousands of others in the universe that researchers believe could potentially sustain life.
"Like most of Kepler's finds, they were discovered via transits -- the shadows they cast toward our solar system as they cross the blazing faces of their stars," reports Scientific American. "Transits allow astronomers to measure a planet's size, orbit and exposure to starlight.
"We can't say for sure whether these planets are truly habitable -- only that they are promising candidates for habitability," said David Kipping, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachussetts.
Kepler 438b is said to be around 12 percent larger than our own planet while receiving 40 percent more starlight. Kepler 442b, on the other hand, is 30 percent larger than Earth and gets about 30 percent more sunlight. These are just a few of the many factors used to determine if a planet is habitable.
Kepler's journey began in 2009, aimed at a patch of stars that were said to house over 150,000 stars. While the primary focus of the mission was to find other Earth-like planets, the craft ran into some technical issues early on. The project was shelved after stabilizer equipment failed in 2013, but scientists figured out a new way to aim the broken telescope, allowing the journey to be resurrected as a "K2" mission.
Originally thought to only take three years, the mission has been extended after star brightness data conjured some unexpected results, but astronomers are back on track with these latest finds. Still, the new mission is admittedly smaller in scope and not as likely to find any more new habitable planets, according to researchers.
"I think these latest planets are about as good as we're going to get from the Kepler data," Kipping says, noting that the team's best chance of finding something is to go back through archival data from 2013 and earlier. "I would like to be surprised-and I'm hopeful-but I'm not sure we'll find planets closer to Earth twins than the objects we present in our paper."
The complete catalogue of potential Earth twins is now at 4,175, according to NASA data, with 554 of those discovered most recently. Only six planets so far are considered the proper size and distance from their stars to be even remotely possible candidates.
NASA is planning a new planet-hunting mission with the upcoming Transiting Exoplanet Survey Satellite (TESS) that is expected to launch in 2017. But scientists admit that this is only the tip of the technological iceberg that could truly confirm the existence of any habitable planet outside of our solar system, and researchers are hoping that 2018's James Webb Space Telescope will get them close enough.
"The impact of this work is to prove that these sorts of worlds are out there," Kipping says. "This is a journey where the end point is investigating planetary atmospheres to look for signs of life, and this result shows it's justifiable to build a space telescope to do exactly that."