Despite being a rogue planet, Cha 1107-7626 is behaving like a “baby planet.” The discovery published in The Astrophysical Journal Letters is a whole new revelation revelation. Although it has only 5–10 times the mass of Jupiter, the FFPMO (free-floating planetary-mass object) behaves like a young star.
In a major episode of stellar accretion (when stars form), this young exoplanet, which is situated in the Chamaeleon Complex around 620 light-years away, is eating material from a nearby disk. For at least two months, astronomers recorded the strongest growth rate ever seen for a planetary-mass object, which was close to 10⁻⁷ Jupiter masses annually, or about 6 billion tons per second.
“People may think of planets as quiet and stable worlds, but with this discovery we see that planetary-mass objects freely floating in space can be exciting places,” said Víctor Almendros-Abad of the National Institute for Astrophysics (INAF), who also described this as the strongest formation episode ever recorded for a planetary-mass object.
Using the James Webb Space Telescope (JWST) and the Very Large Telescope (VLT) at ESO, scientists observed indicators of an EXor outburst, which is typically associated with stars or brown dwarfs, happening on a planetary-mass world.
What astronomers saw
When Cha 1107-7626 was first discovered in 2008, it already had signs of a disk that might supply it with food. Almendros-Abad’s team observed the object and took frequent pictures of it in early 2025. Up until the end of June, everything appeared to be normal. The object’s visible light suddenly increased by a ratio of three to six. That jump matched with the typical spike observed after an important acceleration of stellar accretion, known as an EXor outburst.
The spectrum revealed signs of hydrogen associated with accretion that was magnetically channeled. According to follow-up analyses of older data, this wasn’t a one-off event; a similar outburst happened in 2016, suggesting that Cha 1107-7626 might erupt more often as it develops. In the 2025 burst, the mid-infrared brightness increased a little but the near-infrared brightness remained nearly unchanged, suggesting that the inner disk warmed as more material fell inward.
In the meantime, JWST detected a slight change in the carbon signal and a trace of water vapor, showing that the outburst had altered the chemistry of the disk. These hints together point to a planetary-mass body acting much like a star.
How they captured it
In April, May, and June 2025, the team used the XSHOOTER instrument on the Very Large Telescope (VLT) at ESO. They continued to observe across optical to mid-infrared wavelengths in July and August.
An bigger disk of silicates and hydrocarbons, like the dusty gas disks around newborn stars, had already been discovered by earlier VLT and JWST investigations. Even though the chemistry close to the inner disk changed during the flare, the dust signature stayed constant, which is compatible with a heated inner zone rather than a total disk reconfiguration.
Cha 1107-7626 has amazing star-like behavior because it is just 5-10 Jupiter masses, which is significantly less than the ~80 Jupiter threshold for stars and considerably below the 13 Jupiter masses for brown dwarfs. The information was consistent with the idea that the item developed by direct collapse inside a tiny cloudlet in the Chamaeleon Complex, which is very similar to how stars form on a smaller scale.
A different perspective on rogue planets
Did it originate around a star and then leave? It is challenging to reconcile the results with the very small impulse that would be required to preserve the integrity of such a stable and chemically active disk, according to researchers.
As Amelia Bayo of the ESO notes, the notion that a planetary object may behave like a star is astounding and raises questions about what other worlds might look like in their early phases.