Interstellar Comet 3I/ATLAS is Spewing Gas Surprisingly Slowly, New Observations Show
Astronomers using the Hobby-Eberly Telescope have discovered that the interstellar comet 3I/ATLAS releases gas at half the speed of typical solar system comets. The comet also exhibits unusually high levels of iron and nickel, suggesting unique chemical properties from its interstellar origin.
Why it matters
Studying interstellar objects provides rare insights into the composition of other planetary systems and the conditions of deep space.
Using spectral data from the Hobby-Eberly Telescope in Texas, astronomers have traced gas from the interstellar comet 3I/ATLAS, only the third object of its kind ever observed, out to more than 85,000 km from its nucleus. The data suggest the gas flows at about half the speed typical of solar system comets, and the spectrum shows unusually strong signals of iron and nickel.
The spatial distribution of cyanogen around 3I/ATLAS. Image credit: Cochran et al ., doi: 10.3847/PSJ/aea086.
3I/ATLAS was discovered by the NASA-funded ATLAS survey telescope in Rio Hurtado, Chile, on July 1, 2025.
Also known as C/2025 N1 (ATLAS) and A11pl3Z, the interstellar comet arrived from the direction of the constellation Sagittarius.
On October 30, 2025, the object reached perihelion, its closest approach to the Sun.
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