(Jan Skowron / Astronomical Observatory, University of Warsaw)
Scientists have discovered a Mars-sized rogue planet floating through the Milky Way without a star to orbit, the smallest such planet discovered to date, according to CBS News.
A new study published online Friday in Astrophysical Journal Letters explains how astronomers used gravitational microlensing to discover the planet.
Dr. Prezemek Mróz, a postdoctoral researcher at the California Institute of Technology and a lead author of the study, explained in a news release, "If a massive object – a star or a planet – passes between an Earth-based observer and a distant source star, its gravity may deflect and focus light from the source. The observer will measure a short brightening of the source star."
He added, "Chances of observing microlensing are extremely slim because three objects – source, lens, and observer – must be nearly perfectly aligned. If we observed only one source star, we would have to wait almost a million year to see the source being microlensed."
Dr. Radosław Poleski from the Astronomical Observatory of the University of Warsaw, a co-author of the study, added, "When we first spotted this event, it was clear that it must have been caused by an extremely tiny object."
According to CBS News, scientists don't know precisely what causes rogue planets, but they suspect they formed as a part of a planetary system only to be thrown out by gravitational interaction with other planets.
To detect this planet, the scientists used data from the Optical Gravitational Lensing Experiment survey, which has been surveying the sky for over 28 years.