A new algorithm has uncovered 372 brand new planet candidates in data from the now-defunct Kepler Space Telescope’s K2 mission.
Scientists have unearthed a staggering 372 new exoplanet candidates from data collected by a NASA space telescope that stopped working in 2018.
A keystone mission for exoplanet science, the Kepler Space Telescope launched in 2009 and observed almost 200,000 stars in a tiny patch of sky between 2013 and 2018. Its mission was to calculate what fraction of stars in the Milky Way have Earth-size planets in their habitable zone.
“Kepler stared at one patch of the sky for four years looking for planets transiting across their hosts stars, and from that we could infer information about the period and the radius of each planet,” said Jon Zink , a graduate student working on exoplanets at the University of California, Los Angeles, speaking at this week’s 238th meeting of the American Astronomical Society. “Most of the planets discovered were a little bit larger than Earth and a little bit smaller than Neptune—super-Earths or sub-Neptunes.”
Kepler discovered something incredible— 2,300 exoplanets—which marked a new era in exoplanet research, but it eventually suffered a technical defect. “There was a malfunction that caused the spacecraft to no longer be able to focus on that one patch of sky, so it began looking at different regions of the galaxy,” said Zink.
This K2 mission enabled researchers to study different parts of the galaxy, and stars of different ages and masses, albeit fleetingly. It monitored more than 100,000 more stars by the end of the mission in 2018 when Kepler became unusable.
Artist’s conception of the Kepler Space Telescope. NASA
But the K2 data proved to be too “noisy” for algorithms to automatically “find” candidate exoplanets. So people looked at the data themselves. It worked—to a point. “Human vetting of the datasets found 889 exoplanet candidates, so it was fruitful, but our goal was to fully automate the process,” said Zink.
Its his new algorithms—essentially an automated detection pipeline—that have uncovered this new tranche of exoplanet candidates in the K2 data. “Our code can do it faster, but also more thoroughly—we found 372 new exoplanet candidates in a dataset that’s been sitting around for a few years. They were just waiting to be discovered!” said Zink.
The new code also found 18 multi-planetary star systems and revealed that while the original Kepler mission found about 1.25 planets per star, in the K2 sample that rate was much lower—as low as 0.5 planets per star.
“The big question we want to answer with all these exoplanet discoveries is: how unique is our Solar System?” said Zink. “To answer that we need to understand how planets form and how their orbits evolve over time, so the more planets we have the larger our testbed.”
An exoplanet is one that orbits around a star other than our Sun. Typically they’re found using data that infers their existence, mostly by observing the effect of orbiting planets on the host star. For the Kepler mission that was the transit method, the detecting of a slight dimming in starlight as a planet transits across it.
Wishing you wide eyes and clear skies.