A team of astronomers have found at least 70 planets wandering around space without a host star. Located approximately 420 light-years away from us, this cluster of rogue planets is by far the largest group that has ever been discovered.
Since the majority of planets are detected by gravitational tugs on their host stars or by stellar brightness dips by them passing in front of them (this is known as transiting), the fact that so many worlds have been found without a star is absolutely incredible as they are very hard to spot.
In fact, the manner in which rogue planets are normally found is by a technique known as gravitational microlensing where the planets move in front of stars located in the background. Interestingly, that is not how the astronomers found these new rogue planets. Instead, they studied data and imagery collected over a 20-year period by several ground and space telescopes that include the European Southern Observatory’s Very Large Telescope in Chile, Japan's Subaru Telescope in Hawaii, the European Space Agency’s Gaia Spacecraft, and the Dark Energy Camera on the 4-meter Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile.
According to their study, the astronomers detected infrared energy being produced by 70 to 170 giant gas rogue planets. The exact number is still in question as there are several variables that need to be looked at first, such as the objects that are at least thirteen times larger than Jupiter that are probably not planets and are more than likely brown dwarfs (or “failed stars”). Additionally, they have not calculated the masses of the exoplanets as of yet.
In a statement, Núria Miret-Roig, who is an astronomer at the Laboratoire d’Astrophysique de Bordeaux in France and the University of Vienna in Austria, said, “We did not know how many to expect and are excited to have found so many.” “We measured the tiny motions, the colors and luminosities of tens of millions of sources in a large area of the sky.” “These measurements allowed us to securely identify the faintest objects in this region, the rogue planets.”
And a lot more research needs to be conducted, such as how rogue planets are formed – are they created all alone in space, or were they once part of a solar system but somehow got ejected?
This new discovery seems to suggest that there could possibly be a lot more rogue planets in our Milky Way Galaxy than previously thought and they may even be more common than planets that have host stars. But it’s just a thought for now as that hypothesis has not been proven. A photo of some of the rogue planets can be viewed here.
The study was published in the journal Nature Astronomy.