A rogue planet wandering through the cosmos without a host star has been observed by astronomers going through a substantial growth spurt.
While most of the planets we observe in our Galaxy orbit a star – just like planet Earth does – there are known planets that are not gravitationally bound to one.
One such planet is gathering up cosmic gas and dust from its surroundings at a rate of six billion tonnes a second.
Observing the fast-growing rogue planet
Astronomers identified the fast-growing rogue planet using the European Southern Observatory’s Very Large Telescope, which is one of the most powerful telescopes on the planet, along with data from the James Webb Space Telescope.
The speed at which this rogue planet is growing is the fastest growth rate ever recorded for a planet of any kind.
"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," says Víctor Almendros-Abad, an astronomer at the Astronomical Observatory of Palermo, National Institute for Astrophysics (INAF), Italy and lead author of the study.
The planet has a mass five to 10 times the mass of Jupiter and is 620 lightyears away, located in the constellation Chamaeleon.
It's catalogued Cha 1107-7626, and is still forming.
Gas and dust constantly falls onto the free-floating planet in a process known as accretion.
Yet the study found that the rogue planet is not accreting matter at a steady rate.
By August 2025, the planet was accreting eight times faster than a few months before, at a rate of six billion tonnes per second.
"This is the strongest accretion episode ever recorded for a planetary-mass object," says Almendros-Abad.
Learning more about rogue planets
"The origin of rogue planets remains an open question: are they the lowest-mass objects formed like stars, or giant planets ejected from their birth systems?” says co-author Aleks Scholz, an astronomer at the University of St Andrews, United Kingdom.
The findings suggest some rogue planets may form in much the same way as stars, as accretion bursts like this have been observed in stars before.
Co-author Belinda Damian at the University of St Andrews says: "This discovery blurs the line between stars and planets and gives us a sneak peek into the earliest formation periods of rogue planets."
The team have been able to nail down a few key facts about the rogue planet.
They found that magnetic activity seems to have played a role in driving the dramatic accretion of mass, suggesting that even low-mass objects like this can have strong magnetic fields capable of powering strong accretion events.
The team also found the chemistry of the disc around the planet changed during the accretion burst.
Water vapour was detected during the burst, but not before. Again, this is something that had been spotted in stars before, but never in a planet of any kind.
Co-author and ESO astronomer Amelia Bayo says: “The idea that a planetary object can behave like a star is awe-inspiring and invites us to wonder what worlds beyond our own could be like during their nascent stages.”
