Astronomers discover largest group of ‘rogue planets’ yet

Astronomers just discovered a treasure trove of “rogue planets” — free-floating planets that don’t orbit a star but exist all by their lonesome in the depths of space. With masses comparable to that of Jupiter, the 70 or more rogue planets spotted throughout the Milky Way galaxy are the largest such group of cosmic nomads ever found.

Located within the Scorpius and Ophiuchus constellations, the planets were spotted using a suite of telescopes on both the ground and in space. Typically, rogue planets are difficult to image because they aren’t close to any stars to make them visible. However, with data compiled over 20 years from European Southern Observatory (ESO) telescopes, the European Space Agency’s Gaia satellite, and more, Núria Miret-Roig, an astronomer at the Laboratoire d’Astrophysique de Bordeaux, France and the University of Vienna, Austria, and her team were able to capture faint heat signatures emitted from planets that formed within the last several million years.

The team published its findings on Wednesday in Nature Astronomy.

Location of discovered rogue planets
Image: ESO/N. Risinger (skysurvey.org)

Despite the record-breaking observation, their findings suggest that far more rogue planets are waiting to be seen.

“There could be several billions of these free-floating giant planets roaming freely in the Milky Way without a host star,” Hervé Bouy, an astronomer at the Laboratoire d’Astrophysique de Bordeaux, France and co-author on the study, said in a press release.

The discovery is a step toward figuring out how these mysterious objects form in space, according to an ESO press release. It’s possible rogue planets initially formed around stars before being violently ejected from their solar system. Alternatively, they could have formed from collapsing gas clouds too small to lead to the birth of a new star.

Astronomers are currently awaiting completion of ESO’s Extremely Large Telescope (ELT), a giant observatory that will play a “crucial” part in finding further information about rogue planets, according to Bouy. The ELT is set to begin observations at the end of the decade.