The Milky Way is filled with rogue planets — planets with no stars. But scientists have just found the first-ever small Earth-sized rogue planet.
We have officially found about 4,000 exoplanets so far. Most of them are very different from the planets in our Solar System. However, they have one thing in common — they all orbit at least one star.
Since this website is free of ads, please consider supporting us on Patreon.
The new-found rogue world is slightly smaller than Earth and is floating through the Milky Way alone, with no star to orbit around.
Scientists suspect that billions of free-floating or “rogue” planets may exist in the Milky Way. So far, however, only a handful of candidates have turned up among the 4,000 worlds discovered beyond our solar system.
Most of the rogue planets we have observed appear to be enormous compared to the new-found rogue world. They all measure anywhere from two to 40 times the mass of Jupiter. That’s why astronomers have been puzzled away by the new tiny, free-floating planet.
The potential exoplanet likely has a mass similar to Mars, researchers said in the study published on the arXiv.org repository.
“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.
A few years ago, Polish astronomers from the OGLE team from the Astronomical Observatory of the University of Warsaw provided the first evidence for the existence of such planets in the Milky Way. Writing in Astrophysical Journal Letters, OGLE astronomers announced the discovery of the smallest rogue planet found to date.
Astronomers can only rarely directly observe exoplanets. Usually, they find planets using transit observations which allows them to look at a star and see it dim because another object has crossed in front of it.
You Might Like This: NASA Contacts Voyager 2 Spacecraft
For the new discovery, however, the researchers used another method since the rogue planet doesn’t orbit another star and emit no radiation.
Scientists used the gravitational microlensing technique. This method allows astronomers 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.
“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,” explains Dr. Przemek Mroz, a postdoctoral scholar at the California Institute of Technology and a lead author of the study.
The event, known as OGLE-2016-BLG-1928, is the shortest microlensing event ever, at just 42 minutes. It may mark the smallest rogue planet ever detected. The free-floating planet lies about 27,000 light-years away in the densest part of the galaxy.
According to the study authors, this little world could be the first real evidence that free-floating, Earth-sized planets may be some of the most common objects in the galaxy.
“The odds of detecting such a low-mass object are extremely low,” said Dr. Mroz. “Either we were very lucky, or such objects are very common in the Milky Way. They may be as common as stars.”
Rogue planets may have formed in protoplanetary disks around stars, just like other planets. But eventually, they may have been ejected from their parent planetary systems after gravitational interactions with other planets in the system.