Astronomers have observed Cha 1107-7626, a starless rogue planet, showing an extraordinary growth rate, swallowing up about six billion tons of gas and dust every second through the process of accretion. This is the fastest planetary growth ever recorded.
Understand the naughty planet
Table of Contents
A rogue planet is a planet that floats freely in the galaxy without orbiting a star. They are thought to form around stars and then be ejected, or to form directly from star-like clouds of gas, but fail to gather enough mass to ignite. Because it does not receive starlight, the surface is very cold and dark.
Scientists, led by Víctor Almendros Abad of INAF in Italy, detected Cha 1107-7626 and found that this free-floating world could be a very active place.
Incredible Accretion Surge
In August 2025, the planet showed a spike in material inflow that surged to about eight times the rate measured a few months earlier. This spike:
- It is the strongest accretion episode ever recorded for a planetary mass object.
- Challenges simple planet formation theories and bridges the concepts of planetary growth and young stars, as similar explosions are commonly seen in star formation.
The research team used instruments such as the X-shooter on the Very Large Telescope (VLT) and the James Webb Space Telescope (JWST) to record the spectrum and measure the growth. They found a significant increase in optical and infrared brightness during the explosion.
The naughty planet mimic the growth of the star
The key clue lies in the H-alpha line (H$alpha$ ), which broadens and double-peaks with a dip that shifts to longer wavelengths (redshift).
This profile is a classic sign of magnetospheric accretion, where cold gas falls along a magnetic funnel towards a hot collision region – a mechanism commonly seen in young T Tauri stars.
This shared mechanism suggests that planetary-mass objects utilize the same magnetic pathways to grow as stars.
The accretion spike also changes the mid-infrared spectrum. The hydrocarbon features change shape, and new emissions near 6.6 microns appear, coinciding with the warm water emissions seen in the young disk.
This suggests that the extra energy from accretion heats the surface of the inner disk, directly linking the planet’s chemistry to the accretion event.
Extreme Accretion Rates
Cha 1107-7626’s accretion rate reached about 10^{-7} Jupiter masses per year at its peak. These levels exceed measurements of embedded protoplanets and match high levels rarely seen in some isolated objects.
This event is similar to the explosion of young EXor class stars, which appear quickly and last for weeks to months.
Further observations with future telescopes, such as the Very Large Telescope (ELT), will determine how often and how long explosions like this last. If repeated, these explosions could dominate the way the wandering world grew in its first millions of years.
Source: Earth
