Carbon-Rich Disk Found Around Giant Exoplanet

October 7, 2025Last Updated: October 7, 2025

2 minutes read

Artist's concept of a young exoplanet with a protoplanetary disc, showing molecules involved in moon formation. — An artistic rendering of a dust and gas disc encircling the young exoplanet, CT Cha b, 625 light-years from Earth. Spectroscopic data from the NASA/ESA/CSA James Webb Space Telescope suggest the disc contains the raw materials for moon formation. The planet appears at lower right, while its host star and surrounding protoplanetary disc are visible in the background. [Image description: This is an illustration of a young planet with a surrounding disc of dust and gas, potentially forming moons. The planet, which appears red, is shown at lower right, enveloped by a cloudy disc. The host star appears at upper left, and glows yellow, with its own reddish disc of debris. The black background of space is speckled with stars. At the bottom of the illustration, graphics of molecules are listed in the following order: Acetylene, Carbon Dioxide, Ethane, Benzene, Hydrogen cyanide.]

▼ Summary

– Many Solar System moons have dynamic features like volcanoes, oceans, and geysers, and moon formation is expected to be common across the galaxy.
– Despite the abundance of exoplanets, no clear evidence of exomoons has been found, though hints of moon-forming disks around young exoplanets exist.
– The James Webb Space Telescope detected carbon-rich molecules in a moon-forming disk around a super-Jupiter, contrasting with its star’s water-rich planet-forming disk.
– Detecting actual exomoons relies on observing gravitational effects that cause subtle timing variations in a planet’s orbit as seen from Earth.
– Moon-forming disks are temporary features in young exosolar systems, similar to Saturn’s rings but with material that can form moons or disperse over millions of years.

Many of the fascinating worlds within our own Solar System are not planets at all, but the moons that circle them. These natural satellites boast spectacular features, from erupting volcanoes and vast hydrocarbon seas to powerful geysers and globe-spanning oceans hidden beneath thick layers of ice. The physical principles that govern the formation of large planets strongly suggest that moon formation is a natural and expected outcome. Considering the sheer abundance of planets, our galaxy ought to be overflowing with moons.

So far, however, definitive proof of a moon orbiting a planet outside our Solar System has remained elusive, despite a few promising signals. What astronomers have managed to identify are several very young exoplanets that appear to be encircled by disks of material from which moons could coalesce. In a recent breakthrough, the James Webb Space Telescope has analyzed the disk surrounding a massive super-Jupiter, discovering it is surprisingly abundant in small, carbon-based molecules. This finding is particularly intriguing because the planet-forming disk around the host star is composed primarily of water.

The methods used to hunt for fully-formed exomoons differ significantly from those employed to detect the disks that create them. To find an actual moon, scientists look for its gravitational pull on its host planet. As the moon orbits, it sometimes tugs the planet forward, slightly speeding up its transit, and at other times pulls it backward, causing a delay. These minute gravitational interactions produce tiny, measurable variations in the precise timing of when the planet passes in front of its star from our viewpoint on Earth.

A moon might also block a tiny additional amount of the star’s light at different points in its orbit, but this signal is often extremely difficult to distinguish from the star’s own natural brightness fluctuations.

In contrast, moon-forming disks are a transient feature, present only during the earliest chapters of a planetary system’s life. They resemble larger, more massive versions of Saturn’s famous rings, but they contain sufficient material to eventually clump together and form solid moons. Over the first several million years of a system’s existence, the material in these disks will meet one of several fates: it may be scattered into space, it can coalesce into one or more moons, or it will ultimately spiral inward and crash into the planet itself.

(Source: Ars Technica)