Japanese astronomers claim to have found free-floating “planets” which do not seem to orbit a star. They say they have found 10 Jupiter-sized objects which they could not connect to any solar system. They also believe such objects could be as common as stars are throughout the Milky Way. Using a technique called gravitational microlensing, they detected 10 Jupiter-mass planets wandering far from light-giving stars. Then they estimated the total number of such rogue planets, based on detection efficiency, microlensing-event probability and the relative rate of lensing caused by stars or planets. They concluded that there could be as many as 400b of these wandering planets, far outnumbering main-sequence stars such as our Sun

with this, my personal estimate for the drake equation goes to 8000.

Looking at the Kepler K2 data, the scientists documented 10s of short-duration microlensing events near the galactic core. Of these, 22 were previously detected during the OGLE and KMTnet ground-based campaigns, but 5 signatures hadn’t been seen before. Of these 5, 1 turned out to be a bound exoplanet, but the remaining 4 featured super-short microlensing events consistent with free-floating planets. 1 of the 4 candidate signatures was subsequently detected in ground-based data. The microlensing events, lasting for just several hours, suggest the discovery of unbound exoplanets no larger than Earth. It’s impossible to know what the conditions are like on these presumed rogue exoplanets, but they could be “cold, icy wastelands,” and, if similar in size to Earth, their surfaces would “closely resemble bodies in the outer Solar System, like Pluto.” The new paper suggests the presence of a large population of Earth-sized rogue planets in the Milky Way. It’s becoming clear that free-floating planets are common.

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