A lonely world drifting through space with no star to orbit is gorging on gas and dust at a staggering pace, swallowing roughly six billion tons of material every second during a sudden feeding frenzy last summer. The object, known as Cha 1107-7626, was caught in the act by the James Webb Space Telescope and the European Southern Observatory’s Very Large Telescope, and the observations are forcing scientists to rethink how planets can grow when they have no parent star to guide the process.
“This is the first time we’ve seen an accretion burst on a planetary-mass object,” said Pengyu Liu, a researcher at the European Southern Observatory and lead author of one of the two studies describing the event. The findings were detailed in papers submitted to Astronomy & Astrophysics and posted to the arXiv preprint server in May 2025.
A planet eating like a star
Cha 1107-7626 sits in the Chamaeleon I star-forming region, a dense cloud of gas and dust about 520 light-years from Earth that has long been a hunting ground for young stellar and sub-stellar objects. The object weighs in at only a few times the mass of Jupiter, placing it firmly in planetary territory, yet it is surrounded by its own disk of gas and dust, a miniature version of the disks that encircle newborn stars.
Using JWST’s NIRSpec and MIRI instruments, one research team captured a broad infrared spectrum of the object spanning wavelengths from 0.6 to 12 micrometers. That spectrum revealed hydrogen recombination lines, a telltale signature of gas crashing onto a central body, along with emission from methane and ethylene in the surrounding disk. Detecting hydrocarbons in a disk around a free-floating planetary-mass object is a first. Until now, that kind of chemistry had only been documented in disks around young stars.
A companion study tracked the object’s behavior over several months using the VLT’s X-shooter spectrograph alongside additional JWST data. During April and May 2025, Cha 1107-7626 was quiet, accreting at a low, steady trickle. Then, between June and August 2025, its accretion rate surged by a factor of six to eight, peaking at approximately 10-7 Jupiter masses per year. Translated into everyday terms, that peak rate works out to roughly six billion tons of material slamming into the object every second, a figure highlighted in ESO-affiliated coverage of the discovery.
Young stars routinely undergo similar outbursts, known as FU Orionis or EX Lupi events, where instabilities in a disk dump large amounts of material onto the star over weeks to years. Catching the same phenomenon in an object with planetary mass suggests that the physics of disk accretion scales down smoothly from stars to much smaller bodies. Even isolated planets, it appears, can experience violent growth spurts.
What the chemistry reveals
The methane and ethylene emission lines point to warm molecular gas close to the object, heated either by the shock of infalling material or by radiation from the accretion process itself. These hydrocarbons act as tracers of temperature and density in the inner disk, offering a window into the environment where moons or ring systems might eventually take shape.
Because JWST’s mid-infrared resolution is sharp enough to separate individual molecular features from the broader dust glow, the team could confirm that the signatures belong to real disk chemistry rather than instrumental noise or misidentified spectral lines. Multiple independent lines from the same molecules appeared at the expected wavelengths and relative strengths, bolstering confidence in the detection.
Big questions that remain open
For all the detail in the new data, several important unknowns persist. The exact mass and age of Cha 1107-7626 are not nailed down. Earlier surveys of the Chamaeleon I region, including work on very low-mass members, place the object at a few Jupiter masses, but those estimates rely on evolutionary models that carry significant uncertainty for young, planetary-mass bodies. If the mass sits at the high end of the range, the object might be better classified as a sub-brown dwarf. At the low end, it fits cleanly as a rogue planet. Without a tighter constraint, it is hard to say whether Cha 1107-7626 formed on its own through cloud fragmentation or was kicked out of a planetary system early in its life.
The trigger for the burst is also unclear. In systems with multiple stars, gravitational tugs from a companion can stir a disk and drive material inward. Cha 1107-7626 has no known companion at the resolutions probed so far, so the leading explanation points to thermal or gravitational instabilities within the disk itself: parts of the disk cool, pile up mass, and then suddenly collapse inward. Testing that idea will require watching the object through at least one more quiet-to-burst cycle, and no published observing plan yet covers that full timeline.
The published data end in August 2025, shortly after the inferred peak. Whether the object has returned to its baseline, continued accreting at elevated rates, or entered some new phase of variability is unknown as of May 2026. Regular follow-up observations will be needed to determine whether the 2025 episode was a one-off event or part of a recurring pattern that could dominate the object’s long-term growth.
It is also worth noting that the headline figure of six billion tons per second, while broadly consistent with the measured accretion rate, is a unit conversion that depends on assumptions about the object’s mass, the inner disk radius, and how efficiently gravitational energy converts into observable light. It is best understood as an order-of-magnitude illustration of the event’s scale rather than a precision measurement on par with the spectral detections themselves.
Why rogue planets keep surprising us
Cha 1107-7626 is far from the only free-floating world to challenge assumptions. In 2023, JWST spotted pairs of unbound planetary-mass objects, dubbed Jupiter Mass Binary Objects or “JuMBOs,” drifting through the Orion Nebula, raising questions about how such pairings could form without a host star. Ground-based surveys have identified hundreds of candidate rogue planets across nearby star-forming regions, and some estimates suggest they may outnumber stars in the Milky Way.
What sets Cha 1107-7626 apart is the direct evidence that a rogue planet can actively build itself up through its own accretion disk, complete with complex chemistry and dramatic outbursts. That combination challenges the tidy picture of planets as passive byproducts of star formation. Instead, at least some planetary-mass bodies appear to assemble through their own disks, with episodic bursts that may dominate their early evolution.
Future monitoring of Cha 1107-7626 and similar objects in Chamaeleon I will be critical for determining how common these bursts are, how much total mass they deliver over a young planet’s lifetime, and whether they leave lasting marks on any moons or rings that might one day form around these solitary worlds.
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*This article was researched with the help of AI, with human editors creating the final content.
