may be years old now
though discoveries keep on coming...
It's the first time Earth-sized planets have been spotted using Kepler's little-known microlensing capability.
But one group of planets with similar masses to Earth previously spotted by Kepler don't seem to be gravitationally bound to any stars at all.
Instead, it's a "free-floating planet population," according to results published in a paper in the Monthly Notices of the Royal Astronomical Society.
These objects were either ejected from their original orbits around a star or they could have been birthed from a protoplanetary disk that a star never grew out of, Eamonn Kerins, a senior astronomy lecturer at the University of Manchester and co-author of the study, explained to El Reg.
Star-less planets are rare; only a few dozen candidates have been spotted so far, Kerins said.
The lack of discoveries are down to the techniques space telescopes typically use to find exoplanets, and there are probably more free-floating planet populations out there.
Kepler, for example, was designed to hunt for alien worlds using the transit method, which involves monitoring the characteristic dip in brightness of a star when a planet crosses in front of the sun during its orbit.
Since the majority of exoplanets are found using the transit method, it's no wonder that they're mostly found along with their parent stars.
The most recent four free-floating candidates, however, were detected using microlensing.
For two months in 2016 Kepler took readings from specific sectors in the universe for 30 minutes at a time, to see if microlensing would work.
It did, and the academics found 27 apparently star-less exoplanets, four of which were comparable to Earth.
Lead author of the paper, Iain McDonald, a research fellow at Manchester and an astronomy lecturer at the Open University, said finding these microlensing signals is,
Microlensing is well-suited to finding objects that are very distant.
It's unclear how far away the unmoored planets are. Kerins said they were "well in excess" of being 3,000 light-years away and are probably closer to 10,000 light-years away.
The team hopes that they will be able to confirm the planets are free floaters in the future with telescopes designed to better probe the effects of gravity, dark matter, and energy.