Scientists have discovered another rogue planet, but this one has even experts perplexed: It’s slightly smaller than Earth and is floating through the Milky Way.
The potential exoplanet likely has a mass similar to Mars, researchers said in the study published on the arXiv.org repository. Though rogue planets (those without stars) have been discovered before, they’re extremely hard to spot.
“Our discovery demonstrates that low-mass free-floating planets can be detected and characterized using ground-based telescopes,” the study’s co-author, Prof. Andrzej Udalski, principal investigator of the Optical Gravitational Lensing Experiment (OGLE) project, said in a statement.
More than 4,000 exoplanets have been discovered by NASA in total, most using the transit method. Approximately 50 of them were believed to be potentially habitable as of September 2018, as they have the right size and the right orbit of their star to support surface water and, at least theoretically, to support life.
Transit observations allow astronomers to look at a star and see it dim because another object has crossed in front of it. This type of observation will be expanded when NASA launches its James Webb Space Telescope in October 2021. The telescope was delayed in part because of the coronavirus pandemic, Fox News previously reported.
Another technique, which researchers used in the latest discovery, is “gravitational microlensing,” which allows experts to look as objects in the foreground pass in front of objects in the background. The foreground object acts as a lens, bending and magnifying the light to reveal certain traits about the object in the background.
The event, known as OGLE-2016-BLG-1928, is the shortest microlensing event ever, at just 42 minutes.
“When we first spotted this event, it was clear that it must have been caused by an extremely tiny object,” study co-author Dr. Radoslaw Poleski added.
“Chances of observing microlensing are extremely slim because three objects—source, lens, and observer — must be nearly perfectly aligned,” added the study’s lead author, Przemek Mroz. “If we observed only one source star, we would have to wait almost a million years to see the source being microlensed.”