A strange population of “rogue” (or “free-floating”) planets has been discovered, planets that may be alone in deep space, unattached to any home star.
The study, headed by Iain McDonald of the University of Manchester in the United Kingdom (now at the Open University in the United Kingdom), used data collected in 2016 during NASA’s Kepler Space Telescope’s K2 mission phase.
Kepler examined a crowded field of millions of stars at the core of our Galaxy every 30 minutes during this two-month experiment in order to identify uncommon gravitational microlensing events.
The researchers discovered 27 potential microlensing signals with short durations ranging from an hour to ten days. Many of these have previously been detected in data collected from the ground at the same time.
The four shortest occurrences, on the other hand, are new finds that are compatible with planets with masses close to Earth’s.
These new events do not have a longer signal that would be anticipated from a host star, indicating that they might be free-floating planets.
Such planets might have developed around a host star before being expelled by the gravitational pull of the system’s other, heavier planets.
Predicted by Albert Einstein 85 years ago as a consequence of his General Theory of Relativity, microlensing describes how the light from a background star can be temporarily magnified by the presence of other stars in the foreground.
This results in a brief burst of brilliance that can last anywhere from a few hours to a few days. Microlensing affects around one out of every million stars in our Galaxy at any one time, although only a small percentage of them are thought to be produced by planets.
Kepler was not built to discover planets via microlensing or to investigate the core Galaxy’s incredibly dense star fields. To hunt for signals inside the Kepler dataset, new data reduction techniques have to be created.