The extraordinary finding
A free-floating, or rogue, planet named Cha 1107-7626 is undergoing an immense growth spurt, pulling in gas and dust from its surrounding disk at roughly six billion metric tons per second. Scientists say this is the highest accretion rate ever measured for a planetary-mass object. The discovery, published in The Astrophysical Journal Letters, comes from a concerted observing run that combined data from the ESO’s Very Large Telescope (VLT) equipped with the X-shooter spectrograph and the James Webb Space Telescope (JWST), along with archival observations from VLT’s SINFONI instrument.
Rogue planets, unlike those in our Solar System, do not orbit a star. They drift through interstellar space, making Cha 1107-7626 a rare laboratory for studying planet formation in a setting far from starlight. The team notes that the accretion process in this planet is not steady; in August the rate increased to levels eight times higher than just a few months earlier, underscoring the dynamic, episodic nature of mass growth in these objects.
How the measurements were made
To pin down the extraordinary accretion, researchers exploited a multi-instrument, multi-wavelength approach. X-shooter on the VLT provided spectra across a broad range, while JWST offered infrared insights into the planet’s immediate environment. Archival SINFONI data from the VLT added a complementary view of the surrounding disk material. By comparing the light emitted before and during the growth surge, the team could infer both the rate of material inflow and the physical conditions within the disk.
What the discovery tells us about planet formation
The results challenge a simple dichotomy between planets and stars. Some rogue planets appear to grow via accretion rates and mechanisms that resemble stellar formation, at least during their early phases. The authors highlight that the observed accretion is among the most intense for an object with planetary mass, suggesting that the boundary between planet and star formation may be blurrier than previously thought. The finding also raises the possibility that some planets, including those ejected from their original systems, could experience brief, star-like growth spurts during their youth.
Magnetic activity and sudden accretion
One striking clue is the role magnetic fields may play in fueling such bursts. The team notes magnetic activity likely contributed to the huge inflow of material—an idea previously associated mainly with stars. This hints that even low-mass objects can harbor strong magnetic fields capable of sustaining dramatic accretion events and reshaping our understanding of how young planets interact with their disks.
Water vapor and disc chemistry
During the accretion episode, the chemistry of Cha 1107-7626’s disk changed noticeably: water vapor appeared in the spectrum only during the burst. Water vapor has been observed in accreting stars, but its detection in a planetary-mass object during an accretion event marks a novel occurrence, offering new clues about disk evolution and the conditions that govern early planetary environments.
About Cha 1107-7626
The object is estimated to have a mass five to ten times that of Jupiter and sits around 620 light-years from Earth in the Chamaeleon constellation. It remains in its formative stage, still accreting material from a surrounding gas-and-dust disk. The findings come from a collaboration of 10 scientists, including researchers from the University of Lisbon and other European institutions.
Implications and future directions
As astronomers refine their models of planet formation, Cha 1107-7626 offers a rare window into the possible pathways by which rogue planets can assemble mass and evolve. The study’s coauthors note that this discovery helps close the gap between how stars and planets form at early times, prompting new questions about magnetic fields, disk dynamics, and the ultimate fate of such freely roaming worlds. Ongoing follow-up with JWST and ground-based facilities will seek to catch additional bursts, map the disk structure in greater detail, and determine whether similar episodes occur in other rogue planets.
