The James Webb Space Telescope (JWST) has made a remarkable discovery: six rogue planets, untethered from any star, are wandering through the Perseus molecular cloud, located 960 light-years away. These cosmic vagabonds range in size from five to 10 times the mass of Jupiter, blurring the lines between planets and stars.
The discovery challenges our understanding of planet formation. Typically, planets form from leftover gas and dust after a star is born, creating solar systems like our own. However, these rogue planets seem to have formed directly from collapsing interstellar gas, similar to the process of star formation. This finding suggests that giant planets can form through a variety of mechanisms.
To identify these wandering planets, researchers utilized the JWST’s Near Infrared Imager and Slitless Spectrograph (NIRISS). This powerful instrument allowed them to peer through the dense gas clouds and analyze the infrared light emitted by each object in the star cluster. This method also revealed several known brown dwarfs, objects more massive than planets but smaller than stars, including one with a planet-sized companion.
“We are probing the very limits of the star forming process,” said Adam Langeveld, lead author of the study and an astrophysicist at Johns Hopkins University. “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.”
This isn’t the first time JWST has detected free-floating planets. In 2023, the telescope observed 42 pairs of gas giants, known as Jupiter-mass binary objects (JUMBOs), drifting through the Orion Nebula. These objects further blur the lines between planets and stars, as their masses overlap with gas giants and brown dwarfs.
“It’s likely that such a pair formed the way binary star systems do, from a cloud fragmenting as it contracted,” explained Ray Jayawardhana, senior study author and provost and astrophysicist at Johns Hopkins University. “The diversity of systems that nature has produced is remarkable and pushes us to refine our models of star and planet formation.”
The team plans to continue observing these rogue planets using the JWST, studying their atmospheres and compositions to gain insights into their formation and how they differ from other celestial objects. These observations will contribute significantly to our understanding of planet formation and the diversity of celestial objects in the universe.
