Five years since the Kepler Space Telescope was retired, a team of astronomers believe they’ve found exoplanets captured by some of the veteran observatory’s last light.
Kepler launched to space in 2009 with one essential task: find new worlds. In its nearly decade-long tenure in solar orbit, Kepler found over 2,600 exoplanets, including some that lurk in the so-called “Goldilocks Zone” of habitability, suggesting that they may have conditions suitable for fostering life.
Kepler ran out of fuel in October 2018, and thus the mission ended. But Kepler data still holds cosmic secrets, and this week a team of astronomers announced the discovery of three planets seen by the telescope just before it was retired. The team’s research was published this week in the Monthly Notices of the Royal Astronomical Society.
The planets were observed during the final series of observations by Kepler, a campaign called K2 Campaign 19. Towards the end of its tenure in space, Kepler was increasingly unsteady, making it difficult for the spacecraft to hold its position long enough to take clear data on its observational targets.
Only a week of high-quality data was produced by K2 Campaign 19, at which point the telescope’s data was pretty noisy. The choice to keep Kepler going until the bitter end appears to have paid off, however. “These discoveries demonstrate Kepler’s exoplanet detection power, even when it was literally running on fumes,” the team stated in the paper.
The research team also used the help of the Visual Survey Group, a citizen scientist group that pored over light curves from stars seen by Kepler during the campaign. Dips in the light curve typically indicate a transiting body—namely an exoplanet. Other exoplanet seekers, like the TESS spacecraft, use the same method to search for exoplanets.
Kepler didn’t see the planets, exactly, or at least not that well. Rather, the astronomical team reports three stars that briefly dimmed from Kepler’s perspective, indicating that they had been transitted by an orbiting body. The team identified two of the itinerant bodies to be exoplanets, while the third is an exoplanet candidate.
Both of the confirmed planets are “hot mini-Neptunes,” according to MIT News, meaning they’re a couple times Earth’s size and orbiting close to their host stars. Both worlds are about 400 light-years from Earth, MIT stated. The candidate planet is larger, at nearly four times Earth’s size, and more distant, at about 1,200 light-years from our planet.
“These are the last chronologically observed planets by Kepler, but every bit of the telescope’s data is incredibly useful,” Elyse Incha, an astronomer at the University of Wisconsin at Madison and the study’s lead author, told MIT News. “We want to make sure none of that data goes to waste, because there are still a lot of discoveries to be made.”
The Webb Space Telescope is carrying on Kepler’s mantle as it seeks out exoplanets near and far, increasing astronomers’ understanding of the diversity and prevalence of worlds beyond our solar system. Finding habitable worlds is a top priority for science, according to the latest decadal survey by The National Academies of Sciences, Engineering, and Medicine.