Rogue Planet Accretion: An Unprecedented Growth Spurt
Astronomers have identified an enormous burst of growth in a wandering planet, a rogue world that drifts through interstellar space without a parent star. The object, Cha 1107-7626, is accumulating gas and dust at a staggering rate of about six billion tons per second — the highest accretion rate ever observed for a planet or planet-like body. The discovery, published in The Astrophysical Journal Letters, was made possible with collaborative data from the X-shooter spectrograph on ESO’s Very Large Telescope (VLT) in the Atacama Desert, along with observations from the James Webb Space Telescope (JWST) and archival data from the VLT’s SINFONI instrument.
Cha 1107-7626 lies roughly 620 light-years away in the constellation Chamaeleon and is still in formation, surrounded by a disk of gas and dust that feeds its growth. With a mass estimated at five to ten times that of Jupiter, this rogue planet is not bound to a star, drifting freely through interstellar space as it accumulates mass. The team’s analysis marks the first time such an extraordinary accretion event has been documented for a planetary-mass object.
What makes this growth so remarkable?
The researchers report that the accretion rate was already building in August and rose dramatically within a short period, though it was not constant over time. The magnitude of the surge hints at a highly effective accretion mechanism that, for the first time, appears to be magnetically driven on a planetary-mass body. Lead author Victor Almendros-Abad from the Palermo Observatory notes that the process resembles the most intense accretion episodes seen in young stars, suggesting a possible overlap in how planets and stars gather mass early in their lifetimes.
Magnetic Fields and a Dynamic Disk
The study highlights the potential role of magnetic activity in fueling the burst of material onto the planet. The team found evidence that magnetic fields may have been instrumental, a phenomenon previously associated with stars but now observed in objects with planetary masses. Belinda Damian, a co-author from the University of St Andrews, says that such strong magnetic fields could power dramatic accretion events, bridging the gap between star-like and planet-like behavior in the early stages of a planetary body’s life.
New Chemistry in a Forming World
Around the time of the surge, the chemical makeup of the surrounding disk changed: water vapor was detected during the event but was not present beforehand. This vapor signature parallels observations made in young stars during accretion bursts and marks one of the first times such a chemical shift has been seen in a planetary-mass object, underscoring the complex chemistry that accompanies rapid planet growth.
Broader Implications for Planet Formation
Co-author Aleks Scholz of the University of St Andrews asks whether rogue planets form through a star-like process with relatively low mass or as wide, ejected giants from sunlike systems. The results suggest that some free-floating planets may share formation pathways with stars, at least initially, challenging a strict division between stellar and planetary formation. Amelia Baio, another co-author, emphasizes that these findings push the boundary of how we understand the earliest stages of rogue planets and invite a reassessment of formation models across a spectrum of planetary masses.
Looking Ahead
The team’s observations, combining data from ground-based facilities and JWST, will inform future studies of accretion in low-mass objects. They plan to monitor Cha 1107-7626 to determine whether such explosive growth events recur and how they influence the object’s final mass and composition. The research team comprises ten scientists, including Koraljka Mui, from the Institute of Astrophysics and Space Sciences in Lisbon, Portugal.
About the Object
Cha 1107-7626 is a rogue planet in formation, currently fed by a circumstellar-like disk of gas and dust. Its mass and the intense accretion episode place it in a unique position to illuminate how planets—and perhaps even substellar objects—gain mass in the absence of a central star.
