Earth-sized rogue planet found floating in the Milky Way
   Date :02-Nov-2020

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SCIENTISTS have discovered in the Milky Way an Earth-sized free-floating rogue planet which does not orbit any star. Rogue planets are a bit uncommon as although many of the known exoplanets discovered so far do not resemble those in our solar system, they have one thing in common -- they all orbit a star. However, theories of planet formation and evolution predict the existence of free-floating (rogue) planets, gravitationally unattached to any star.
Polish astronomers from the Astronomical Observatory of the University of Warsaw provided the first evidence for the existence of such planets in the Milky Way a few years ago. However, the newly-detected planet, detailed in the Astrophysical Journal Letters, is the smallest rogue world ever found, according to the scientists. “Our discovery demonstrates that low-mass free-floating planets can be detected and characterised using ground-based telescopes,” said study co-author Andrzej Udalski, Professor at University of Warsaw in Poland. Exoplanets can be only rarely directly observed. Usually, astronomers find planets using observations of the light from the planet’s host star.
For example, if a planet crosses in front of its parent star’s disk, then the observed brightness of the star periodically drops by a small amount causing so called transits. Astronomers can also measure the motion of the star caused by the planet. Free-floating planets emit virtually no radiation and -- by definition -- they do not orbit any host star, so they cannot be discovered using traditional methods of astrophysical detection.
Nevertheless, rogue planets can be spotted using an astronomical phenomenon called gravitational microlensing. Microlensing results from Einstein’s theory of general relativity -- a massive object (the lens) may bend the light of a bright background object (the source). The lens’ gravity acts as a huge magnifying glass which bends and magnifies the light of distant stars.