An intriguing new study from Interstellar Visitor 3I/ATLAS has revealed that the object’s chemical composition changed significantly during its recent transit through our Solar System, providing a rare glimpse into another star system.
Using the Subaru Telescope on Maunakea, a team led by researcher Yoshiharu Shinaka observed the comet on January 7, 2026.
By analyzing the comet’s coma – the cloud of gas surrounding its core – the team discovered a surprising change in the ratio of carbon dioxide and water.
The ratio changed significantly after the comet’s perihelion on October 29, 2025. This suggests that as the Sun’s radiation penetrated deeper into the comet, it began to sublimate various layers of the object.
“By applying the observational and analytical techniques we have developed through the study of Solar System comets to interstellar objects, we can now directly compare comets from both inside and outside the Solar System and detect differences in their composition and evolution,” team leader Yoshiharu Shinaka of the Koyama Space Science Institute in Japan said in a statement.
The findings show that 3I/ATLAS is not a uniform “dirty snowball”, but rather an object with a chemically diverse internal composition. Meanwhile, the team’s data shows that the chemistry on the comet’s surface is different from the ancient materials buried deep within its core.
While 3I/ATLAS is not only the third interstellar object ever discovered, its chemical signatures act as a time capsule from a distant, unknown stellar system.
In this regard, Shinnaka said: “Through the study of such objects, we hope to gain a deeper understanding of how planets and planetesimals form in a variety of stellar systems.”
“With full-scale operation of survey telescopes in the coming years, many more interstellar objects are expected to be discovered,” Shinnaka said.
“Through the study of such objects, we hope to gain a deeper understanding of how planets and planetesimals form in various stellar systems, including our own Solar System.”
With new high-powered survey telescopes coming into operation, astronomers expect an increase in discoveries of interstellar objects that will further elucidate the building blocks of the galaxy.
