This garage-sized space telescope spent almost 10 years searching for Earth-sized planets in far flung solar systems, and although it’s been retired for about five years, scientists are still discovering new findings from its final days.
”These are fairly average planets in the grand scheme of Kepler observations,” said Elyse Incha, an astronomer at the University of Wisconsin-Madison, US.
“But they’re exciting because Kepler observed them during its last few days of operations. It showcases just how good Kepler was at planet hunting, even at the end of its life.”
The smallest planet, K2-416 b, orbits a red dwarf star and is approximately 2.6 times Earth’s size.
K2-417 b is next. It’s more than three times Earth’s size, also orbiting a red dwarf but faster than K2-416 b.
The final planet – which is yet to be confirmed – is called EPIC 246251988 b. It’s almost four times the size of Earth and orbits its Sun-like star every 10 days.
This trio of planets was discovered as part of the Visual Survey Group citizen scientist project, a small group which regularly looks through NASA telescope data. The citizen scientists searched records from Kepler’s final campaign for changes to the light curves that can be telltale signs of planets.
“People doing visual surveys – looking over the data by eye – can spot novel patterns in the light curves and find single objects that are hard for automated searches to detect, and even we can’t catch them all,” said Tom Jacobs, one of the Visual Survey Group team members.
“I have visually surveyed the complete K2 observations three times, and there are still discoveries waiting to be found.”
The team found one transit – a star dimming slightly when a planet or other object passes in front of it, when viewed by a telescope – for each of the three potential planets.
Looking back on other, lower-quality data from the telescope’s final days revealed one more transit for two of the planets. This means that one is a single transit candidate, while the other two are genuine exoplanets.
“The second transits for those two planet candidates helped us confirm their discovery,” said Assistant Professor Andrew Vanderburg, an MIT astrophysicist.
“No one had found planets in this dataset before, but our collaboration was able to find three. And we’re really pushing up against the last few days, the last few minutes, of observations Kepler collected.”