The James Webb Space Telescope (JWST) has spotted six rogue planets drifting freely through space, untethered from the gravity of any companion stars.
The planets are wandering through the Perseus molecular cloud 960 light-years away and range in size from five to 10 times the mass of Jupiter.
The strange cosmic vagabonds are evidence that gigantic planets can form in much the same way as stars — congealing directly from turbulent clouds of collapsing interstellar gas, scientists said. The researchers' findings have been accepted for publication in The Astronomical Journal and are available on the preprint server arXiv.
"We are probing the very limits of the star forming process," study lead author Adam Langeveld, an astrophysicist at Johns Hopkins University, said in a statement. "If you have an object that looks like a young Jupiter, is it possible that it could have become a star under the right conditions? This is important context for understanding both star and planet formation."
Typically, planets form from the leftover gas and dust used in the formation of stars, creating solar systems such as our own. But not every planet is made by this process: Sometimes gigantic planets can form directly from gas collapse, the study authors said.
To spot the wanderers, the researchers used the JWST's Near Infrared Imager and Slitless Spectrograph (NIRISS) to peer through the billowing gas clouds and analyze the infrared light profile of every object in the observable portion of the star cluster. Using this method, the researchers also spotted a number of known brown dwarfs — strange objects that are more massive than the largest planets but smaller than the smallest stars — including one accompanied by a planet-size object.
"We used Webb's unprecedented sensitivity at infrared wavelengths to search for the faintest members of a young star cluster, seeking to address a fundamental question in astronomy: How light an object can form like a star?" senior study author Ray Jayawardhana, provost and astrophysicist at Johns Hopkins University, said in the statement. "It turns out the smallest free-floating objects that form like stars overlap in mass with giant exoplanets circling nearby stars."
This isn't the first time that JWST has spotted freely floating planets in space. The biggest haul came in 2023, when 42 pairs of the gas giants — known as Jupiter-mass binary objects or JUMBOs — were observed drifting through the Orion Nebula. These objects blur the boundaries between what is a planet and what is not, as many of their masses overlap with gas giants and brown dwarves.
"It's likely that such a pair formed the way binary star systems do, from a cloud fragmenting as it contracted," Jayawardhana said. "The diversity of systems that nature has produced is remarkable and pushes us to refine our models of star and planet formation."
The researchers said their next steps will be to follow the objects with the JWST, studying their atmospheres and compositions for clues about their formation and how they differ from other cosmic objects.
