Interstellar Comet 3I/ATLAS Reveals Methane on Solar Journey

The rare interstellar visitor provided a unique opportunity for the James Webb Space Telescope to study its chemical composition.

Apr. 17, 2026 at 2:56am

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A highly structured abstract painting in muted earth tones, featuring sweeping geometric arcs, concentric circles, and precise botanical spirals, conceptually representing the complex chemical forces and composition of the interstellar comet 3I/ATLAS.The James Webb Space Telescope's analysis of the interstellar comet 3I/ATLAS revealed the presence of methane, providing a rare glimpse into the chemical composition of a planetary system beyond our own.Eureka Today

Interstellar comet 3I/ATLAS, only the third such object detected from outside our solar system, is now on its way out after looping around the Sun in October 2025. Using the advanced instrumentation of the James Webb Space Telescope, researchers were able to analyze the comet's mid-infrared signatures and detect the presence of methane, providing insights into the distant planetary system where 3I/ATLAS originated.

Why it matters

Interstellar objects like 3I/ATLAS offer a rare chance to study the composition of planetary systems beyond our own, as they contain different ratios and compounds compared to objects in our solar system. The data gathered by the James Webb Space Telescope on 3I/ATLAS can help expand our understanding of how other planetary systems form and evolve.

The details

3I/ATLAS is over a kilometer wide and is made up of dust and ices from the far-off planetary system where it originated. As the comet approached the Sun, its surface ices began to outgas, allowing researchers to detect the presence of methane using the James Webb Space Telescope's mid-infrared instruments. This change in methane emissions indicated that 3I/ATLAS was shedding its ancient outer surface and exposing its inner icy layers as it was warmed by the Sun.

  • In October 2025, 3I/ATLAS looped around the Sun within 1.5 AU (one AU is the distance between the Earth and the Sun).
  • As of April 2026, 3I/ATLAS is now past the orbit of Jupiter on its way out of the solar system.

The players

3I/ATLAS

An interstellar comet that is over a kilometer wide and made up of dust and ices from a distant planetary system.

James Webb Space Telescope (JWST)

An advanced space observatory with sophisticated instrumentation that was used to analyze the mid-infrared signatures of 3I/ATLAS.

Matthew Belyakov

A Caltech graduate student and lead author on the paper describing the JWST's findings on 3I/ATLAS.

Mike Brown

The Richard and Barbara Rosenberg Professor of Planetary Astronomy and Terence D. Barr Leadership Chair and director of the Center for Comparative Planetary Evolution at Caltech.

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What they’re saying

“It's a very interesting object. It has been traveling through the galaxy for at least a billion years. The high speed at which it flew past us gave just a narrow window to study it.”

— Matthew Belyakov, Caltech graduate student

What’s next

The team plans to observe 3I/ATLAS one more time this spring using the James Webb Space Telescope before the comet becomes too faint to study.

The takeaway

Observations of the interstellar comet 3I/ATLAS using the advanced instruments of the James Webb Space Telescope have provided a rare glimpse into the chemical composition of a planetary system beyond our own, expanding our understanding of how other solar systems form and evolve.