Kepler ran out of fuel in 2018 and, in its death throes, managed to find three planets before its total shutdown.

Astronomers, with the help of citizen scientists, have discovered what may be the last planets the Kepler space telescope observed before it ran out of fuel in 2018. The team, led by researchers from MIT and the University of Wisconsin-Madison, reviewed the past week of high-quality data from the telescope and detected three stars, in the same part of the sky, that appeared to dim briefly. The scientists determined that two of the stars each host a planet, while the third hosts a planet “candidate” that has yet to be verified.

The two validated planets are K2-416 b, a planet about 2.6 times the size of Earth that orbits its star every 13 days, and K2-417 b, a slightly larger planet that has a just over three times the size of Earth and revolving around its star every 6.5 days. Because of their size and proximity to their stars, both planets are considered “hot mini-Neptunes.” They are about 400 light years from Earth.

The planet candidate is EPIC 246251988 b, the largest of the three worlds at nearly four times the size of Earth. This Neptune-sized candidate orbits its star in about 10 days and is slightly farther, 1,200 light-years from Earth. “We have found what are likely the last planets ever discovered by Kepler, in data taken while the spacecraft was literally on its last legs,” Andrew Vanderburg, an assistant professor of physics at MIT’s Kavli Institute for Astrophysics and Space Research, says in a statement. . “The planets themselves are not particularly unusual, but their atypical discovery and historical importance make them interesting.”

Source: The Monthly Notices of the Royal Astronomical Society.