The next time you gaze at the constellation Lyra, ponder the possibility that someone might be gazing back.
On Thursday, astronomers working on NASA's Kepler mission announced the discovery of two planets orbiting a star in the distant constellation that could theoretically harbor life.
"These are the most Earth-like planets ever discovered," says San Diego State University astronomy professor William Welsh, one of the dozens of scientists who helped confirm the planets' existence.
The two planets are named Kepler 62e and Kepler 62f. They reside in what astronomers call the habitable zone — a region not so distant from a sun-like star that water would freeze, but not so close that it would evaporate.
Both of the planets are larger than Earth (62e is 60 percent bigger and 62f is 40 percent larger). And they're each closer to their sun than the Earth is to ours (a year on 62e elapses in 122 days; it takes 267 days on 62f).
This marks a major milestone for the Kepler space telescope, launched in 2009 with the mission of seeking out Earth-like planets beyond our own solar system.
Previously discovered planets in the habitable zone have typically been gaseous giants. They might have a temperature suitable for life, but they would lack the solid surface needed to ground life.
Based on the size and estimated temperatures of Kepler 62e and 62f, NASA researchers believe they could be rocky worlds containing liquid water. And that combination could be friendly to the emergence of life.
All that is speculative though. Detecting real signs of life would require a detailed analysis of the planets' atmospheric composition.
"Chemicals in certain combinations are very indicative of biological activity," says Jerome Orosz, another SDSU professor on the Kepler team. "For example, oxygen and methane together should not exist unless there's something creating it."
But Orosz says it will likely take "years to decades" to find such chemical markers. And that's only if NASA can secure the funding needed for such an expensive project.
So for the time being, we can only speculate about the possible life on these planets. But who could resist speculating? The planets orbit a star that's three billion years older than our sun.
"That means that life on these planets may have been around for billions of years longer than we've had here on our Earth," notes Welsh. "The implications for that? We don't really know. But if intelligent life develops, it could be very advanced."
Don't start packing your bags for these temperate water worlds, though. At 1,200 light years away, the planets are well beyond human reach. "It would take about 21 million years of travel to get there," says Welsh.
