Astronomers saw a rogue planet going through a rapid growth spurt

A rogue planet situated approximately 600 light-years away is undergoing an extraordinary phase of growth, consuming gas and dust at an astounding pace of 6 billion metric tons per second, according to a study published on October 10 in Astrophysical Journal Letters. This planet, which does not orbit any star, has set the record for the fastest growth rate observed in any planet—regardless of whether it has a host star—and sheds light on the formation processes of free-floating planets.

Astronomers first detected this young rogue planet, designated Cha 1170-7626, nearly two decades ago in the southern constellation Chamaeleon. Estimated to be five to ten times more massive than Jupiter, the planet is amassing mass by drawing in material from an adjacent disk of gas and dust, explains astronomer Victor Almendros-Abad from the Palermo Astronomical Observatory in Italy.

Almendros-Abad and his research team aimed to explore the progression of rogue planets, which may have originated around parent stars like conventional planets, only to be ejected from their original systems, or developed in isolation from collapsing gas clouds, akin to star formation.

Earlier this year, the scientists analyzed the ultraviolet, visible, and infrared light emitted by Cha 1170-7626 and its surrounding disk using the Very Large Telescope (VLT) in Chile. Observations conducted in April and May indicated a consistent growth rate. However, light patterns observed in late June suggested that the rogue planet had suddenly ramped up its consumption, rapidly acquiring material along its magnetic field lines.

Subsequent data from the VLT and the James Webb Space Telescope from July and August allowed the researchers to estimate that Cha 1170-7626 was gathering matter at a rate up to eight times greater than just a few months earlier. The temperatures of the planet’s surface and the surrounding gas and dust increased, and the disk exhibited signs of water vapor that were absent in earlier observations.

Many characteristics of this feeding frenzy—particularly its lengthy duration from late June to August—are reminiscent of a rare growth spurt previously observed predominantly in young stars, suggesting that the rogue planet might have experienced a stellar-like formation. Furthermore, data collected in 2016 indicate that Cha 1170-7626 may engage in this gluttonous behavior on a regular basis.

Almendros-Abad plans to observe the solitary planet again later this year to determine if it is still in this phase of rapid accumulation. “Yet, a single discovery alone does not provide a comprehensive understanding of the broader context,” he notes. The team intends to identify more rogue planets during such gluttonous episodes to evaluate the frequency and duration of these phenomena.