A new intriguing study of the interstellar visitor 3I/ATLAS has revealed that the object’s chemical composition shifted 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 Shinnaka 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 shift in the ratio of carbon dioxide to water.
The ratio changed notably following 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 different layers of the object.
“By applying the observational and analytical techniques we have developed through studies of solar system comets to interstellar objects, we can now directly compare comets hailing from both inside and outside the solar system and explore differences in their composition and evolution,” team leader Yoshiharu Shinnaka, of the Koyama Space Science Institute in Japan, said in a statement.
The findings imply that 3I/ATLAS is not a uniform “dirty snowball” but rather an object with a chemically diverse internal structure. Meanwhile, the team’s data shows that the chemistry on the comet’s surface differs from the ancient materials buried deep within its core.
While 3I/ATLAS is not only the third interstellar object ever detected, its chemical signatures act as a time capsule from a distant, unknown stellar system.
In this regard, Shinnaka said: “Through studies of such objects, we hope to gain a deeper understanding of how planetesimals and planets formed in a wide variety of stellar systems.”
“With the full-scale operation of survey telescopes in the coming years, many more interstellar objects are expected to be discovered, “Shinnaka said.
“Through studies of such objects, we hope to gain a deeper understanding of how planetesimals and planets formed in a wide variety of stellar systems, including our own solar system.”
With new high-powered survey telescopes entering operation, astronomers expect a surge in discoveries of interstellar objects that will further decode the building blocks of the galaxy.
