A Rogue Planet Growing at an Astonishing Rate of 6 Billion Tonnes Every Second! Imagine a planet drifting alone through the vastness of space, not tethered to any star, yet rapidly gaining mass at a mind-boggling pace. This is exactly what an international team of astronomers has discovered using the European Southern Observatory’s Very Large Telescope (ESO’s VLT). They have identified a rogue planet, named Cha 1107-7626, that is breaking records by accumulating matter at an incredible rate of 6 billion tonnes per second. But here’s where it gets controversial: what does this rapid growth tell us about the nature and origins of such mysterious wanderers?
Rogue planets, also known as free-floating planets, are planetary-mass objects that roam the galaxy independently, without being gravitationally bound to any star or brown dwarf. These elusive bodies were only first detected in the year 2000, making them a relatively recent discovery in astronomy. Despite their late arrival on the scientific scene, estimates suggest there could be trillions of these nomads in our Milky Way galaxy—potentially outnumbering stars by a factor of 20. This staggering number challenges our traditional understanding of planetary systems and raises questions about how many planets might be wandering the cosmos unseen.
These free-floating planets vary widely in size and composition. While many are thought to be rocky and relatively small, Cha 1107-7626 occupies a fascinating middle ground. It has a mass estimated to be between five and ten times that of Jupiter. This is significant because it’s not massive enough to ignite deuterium fusion in its core—a process that would classify it as a brown dwarf, a type of sub-stellar object with a mass ranging from about 13 to 80 times Jupiter’s. So, Cha 1107-7626 sits right on the borderline, making it a key object for studying the blurry line between planets and brown dwarfs.
What makes Cha 1107-7626 even more intriguing is that it’s still actively growing. Observations from both the VLT and the James Webb Space Telescope (JWST) revealed that this rogue planet experienced sudden brightening events during April-May and June-August of 2025, increasing in brightness by roughly 1.5 to 2 magnitudes. This flare-up corresponds to a dramatic 6 to 8 times increase in the rate at which the planet is pulling in material, reaching an unprecedented accretion rate of 10^-7 Jupiter masses per year—the highest ever recorded for a planetary-mass object.
These findings open up new avenues for understanding how rogue planets form and evolve. One of the biggest mysteries remains: how do these planets end up drifting alone in space? Are they the smallest objects formed through star-like processes, or are they giant planets that were ejected from their original star systems? Professor Aleks Scholz from the University of St Andrews, a co-author of the study, highlights this ongoing debate, emphasizing that the origin of rogue planets is still an open question.
The bursts of brightness observed in Cha 1107-7626 resemble a phenomenon known as EXor outbursts, named after the young star EX Lupi, which exhibits repeated, short-lived increases in brightness. To put it simply, young low-mass stars often gain much of their mass during brief, intense episodes of accretion—periods when they rapidly pull in surrounding material. These episodes come in two main types: FUor and EXor outbursts. FUor events are dramatic, with stars brightening by about 5 magnitudes over a year and staying bright for decades. EXor outbursts, on the other hand, are less intense but more frequent, with smaller brightness increases over shorter timescales.
By the end of their monitoring, the research team noted that the burst in Cha 1107-7626 was still ongoing. Their analysis of archival VLT data also showed consistently high accretion levels, suggesting that this rogue planet experiences these bursts regularly. The team’s paper points out that the observed event doesn’t match the typical variability seen in young stars but aligns well with the characteristics of an EXor-type burst. This makes Cha 1107-7626 the first substellar object with evidence of potentially recurring EXor bursts, although its accretion variability is unusually strong compared to young stars.
Dr. Belinda Damian, another co-author and astronomer at the University of St Andrews, remarks that this discovery blurs the traditional boundaries between stars and planets. It offers a rare glimpse into the earliest stages of rogue planet formation, a phase that has remained largely hidden until now.
The full study detailing these groundbreaking observations has been published in The Astrophysical Journal Letters.
So, what do you think? Could rogue planets like Cha 1107-7626 be the missing link in our understanding of planetary formation, or do they represent a completely different class of celestial objects? And if they are still growing so rapidly, what does that mean for their future evolution? This discovery challenges long-held definitions and invites us to rethink the cosmic dance between stars and planets. Share your thoughts and join the conversation—are rogue planets just runaway planets, or something far more intriguing?
