An international team of astronomers has documented an explosive growth phase in a rogue planet, Cha 1107-7626, a world that wanders interstellar space, unbound to any star. The object is accumulating gas and dust from a surrounding disk at a rate of six billion tonnes per second, the highest accretion rate ever recorded for an object with planet-like mass. The discovery, published in The Astrophysical Journal Letters, was revealed with data from several powerful observatories, underscoring how even free-floating planets can experience dramatic early growth.
Record-Breaking Accretion Burst
The extraordinary surge occurred while Cha 1107-7626 was still forming, with its mass estimated to be five to ten times that of Jupiter. The rate of material inflow is not constant; in August the planet appeared to be accreting about eight times faster than just a few months earlier, signaling a highly dynamic early life stage for this rogue world. Such rapid accretion during a planet-mass object’s youth mirrors some of the most energetic processes seen in star formation, prompting astronomers to rethink long-held boundaries between planets and stars.
How the Discovery Was Made
Researchers pieced together observations from multiple facilities to track the surge in real time. The X-shooter spectrograph on the Very Large Telescope (VLT) provided a broad view of the light emitted by the system, while data from the James Webb Space Telescope (JWST) offered infrared insights into the disk’s composition and temperature structure. Archival spectra from the VLT’s SINFONI instrument complemented the dataset, enabling a detailed view of the evolving chemistry around the infant planet. Located about 620 light-years away in the Chamaeleon constellation, Cha 1107-7626 is still embedded in its natal gas-and-dust disk, making it an ideal laboratory for studying planet formation in a rogue environment.
What This Means for Planet Formation
The magnitude and variability of the accretion episode suggest that some rogue planets may share a formation pathway with stars, at least early on. Astronomers have already observed sudden, high-rate accretion events in young stars; seeing a similar mechanism in a planet-mass object blurs the line between the two classes. “We tend to think of planets as quiet, stable worlds, but freely wandering objects can be incredibly dynamic,” said the study’s lead author, Víctor Almendros-Abad, a researcher at the Oscillatorio Astronómico de Palermo. The findings imply magnetically driven accretion could power such bursts in low-mass objects, a scenario previously only associated with more massive stellar companions.
Belinda Damian, a coauthor from the University of St Andrews, notes that the event “esbatea the line between stars and planets,” drawing us closer to understanding the earliest phases of rogue planet formation. The team also found that the disk’s chemistry shifted during the burst, with water vapor detected only during the outburst, a signature previously seen in some young stars but not in planets. “The appearance of water vapor during the event indicates a dynamic, heated disk environment,” added another coauthor, Amelia Baio, from the same institution. Aleks Scholz of the University of St Andrews raises a key question: do rogue planets form like stars and later shed mass, or are they giant planets expelled from their birth systems?
Implications and Future Questions
These observations hint at a potential continuum in substellar formation that spans from giant planets to low-mass stars. If magnetic fields of relatively small mass bodies can sustain such energetic accretion, our models of early planetary evolution may need revision. The case of Cha 1107-7626 shows that even objects that float freely through interstellar space can have tumultuous, star-like beginnings. The study’s authors—including 10 scientists with contributions from Koraljka Mužić of the Instituto de Astrofísica e Ciências do Espaço (Portugal)—emphasize that continued monitoring of this system will be crucial for deciphering how common such events are among rogue planets and what they reveal about the diversity of planetary birth environments.
People Behind the Findings
The research team comprises researchers from multiple institutions across Europe and beyond, reflecting a collaborative effort to harness data from cutting-edge observatories. The combination of ground-based spectroscopy and space-based infrared observations enabled a comprehensive view of the accretion process and its impact on the surrounding disk. As astronomers push toward even more sensitive instruments, further studies of Cha 1107-7626 and other rogue planets are likely to shed light on whether star-like formation processes are a broader feature of the rogue planet population or if this event remains exceptional.
