Earlier this year, the Inquisitr reported on the discovery of a giant rogue planet floating just 20 light-years away from Earth. Unlike most planets, this particular celestial body doesn't orbit a star and was found wandering alone through the cosmic darkness, detected by radio telescopy.
Now, astronomers have announced that they have found two more rogue planets in our galaxy — starless voyagers that dwell in perpetual night, roaming the void all by themselves.
According to New Scientist, the two free-floating planets were found by Polish astronomers from Warsaw University, who detected the planetary bodies in data from the Optical Gravitational Lensing Experiment (OGLE) survey at the Las Campanas Observatory in Chile.
"Planet formation theories predict the existence of free-floating planets, ejected from their parent systems. Although they emit little or no light, they can be detected during gravitational microlensing events," the team explain in a new study, published last week on the preprint server arXiv.
While most planetary discoveries are made using a technique called the transit method — which looks for dips in a star's brightness to spot an orbiting planet passing (transiting) in front of it, the Inquisitr previously reported — finding rogue planets is a lot trickier.
This is because these lone celestial nomads are not tethered to a star which they can transit and temporarily dim out, thereby alerting astronomers to their presence. In their case, scientists rely on gravitational microlensing — an astronomical phenomenon that shines light on hidden planets when they happen to cross paths with starlight coming from far-flung stars.
When a planet drifts in the path of a distant star's light, its gravitational pull causes the starlight to warp and distort, notes Futurism. This effect can be spotted by Earth-bound observers and can lead to the detection of exoplanets that otherwise would have gone unnoticed.
The method has been used before to find planets lurking outside of our solar system — and even beyond the borders of the Milky Way, as reported by the Inquisitr earlier this year.
The same technique helped OGLE pick up one of the newfound rogue planets on April 16, 2017. The detection was later confirmed as a planetary body through follow-up observations from other observatories, reports Motherboard.
Dubbed OGLE-2017-BLG-0560, this object is enormous and could either be "a Jupiter-mass planet in the galactic disk or a brown dwarf in the bulge," with up to 20 times the mass of Jupiter, detail the astronomers.
Intrigued by this exciting find, the team combed through the OGLE archive and stumbled upon yet another rogue planet. Known as OGLE-2012-BLG-1323, this planet was originally detected on August 21, 2012, but simply fell through the cracks and was overlooked until now.
Unlike the 2017 find, this rogue is considerably smaller — in fact, it's the smallest planet ever found to wander the universe alone — and has an estimated mass ranging between that of Earth and Neptune.
Only about a dozen rogue planets have ever been uncovered so far, although astronomers suggest that the Milky Way could host more starless planets and actual stars.