Astronomers have discovered a host of habitable planets hiding in data from the Kepler space telescope, which may include some of the best candidates for finding life outside the Solar System.
The data comes from Kepler’s first run of observations, from 2009 to 2013, when the telescope was pointed at one region of the sky.
Led by Susan Thompson from the SETI Institute in California, the team found 20 promising candidates for Earth-like worlds, orbiting Sun-like stars on similar orbits to our own. A pre-print of their findings is available on arXiv.
One in particular, KOI-7923.01, looks particularly promising. It is 97 percent the size of Earth, and orbits its star in 395 days. It’s slightly further from its star than Earth is from the Sun, which means it is likely a bit colder than our planet, with tundra-like conditions.
“If you had to choose one to send a spacecraft to, it’s not a bad option,” Jeff Coughlin from NASA’s Ames Research Center, a co-author on the paper, told New Scientist.
To confirm an exoplanet, Kepler needs to observe three dips in a star’s light as a planet passes in front of it, known as a transit.
For this reason, many of the planets Kepler has found so far are mostly on short orbits, some lasting just several Earth days, as these are easier to confirm.
But for true Earth-like planets, those around Sun-like stars, habitable worlds are likely to have a similar orbit to our own. That is, one lasting about an Earth year.
These longer orbits mean Kepler was only able to spot the dips in light once or twice in its initial run. After one of the telescope’s reaction wheels broke in 2013, it was pointed towards other targets as part of its K2 mission.
In that first batch of data, however, there are a number of candidate exoplanets that look like pretty good bets for habitability. Kepler is unable to confirm that these planets truly exist, but follow-up observations from telescopes like Hubble could prove that they do.
For these new worlds, there is a 20 to 30 percent chance that some of them will turn out to be blips in data, rather than true planets. Nevertheless, this makes them prime candidates for further study.
While we’ve discovered a number of interesting planets around red dwarfs, we simply don’t know if such worlds can support life. However, we know of one place that does support life, Earth, and that orbits the Sun. Finding others with similar characteristics will be key.