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Comet 3I/ATLAS

Cataloguing the journey of comet 3I/ATLAS through the solar system. Because the object comes from outside our solar system, it is just passing through – so we use all the tools at our disposal to observe it before it disappears back into the cosmic dark. A host of NASA missions are coming together to observe this interstellar object, which was first discovered in summer 2025, before it leaves forever. While the comet poses no threat to Earth, NASA’s space telescopes help support the agency's ongoing mission to find, track, and better understand solar system objects.

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NASA’s PUNCH Spies Interstellar Comet 3I/ATLAS

NASA’s PUNCH (Polarimeter to Unify the Corona and Heliosphere) mission observed interstellar comet 3I/ATLAS during its passage through the inner solar system.

The mission’s ability to observe areas of the sky near the Sun allowed PUNCH to track the comet as it passed close to our star, when few other observatories could.

A round, white object appears at the center of a black-and-white image, with a short tail-like feature extending to the right. Fuzzy black, white, and gray diagonal, parallel stripes fill the background.
Comet 3I/ATLAS appears as a bright object near the center of this image, made from combining observations from NASA’s PUNCH mission taken from Sept. 20 to Oct. 3, 2025, when the comet was about 231 million to 235 million miles from Earth. Its tail appears as a short elongation to the right. Stars appear as streaks in the background. 
NASA/Southwest Research Institute

This image was created from multiple observations taken by PUNCH from Sept. 20 to Oct. 3 that were stacked to make the comet stand out against the background stars, which appear as streaks in the image.

The PUNCH observations reveal the comet’s tail, visible as a slight elongation to the lower right. 

The comet was very faint during these observations, so the PUNCH team was not sure whether the spacecraft would be able to see it clearly, as PUNCH is designed to study the Sun’s atmosphere and solar wind — not comets. However, stacking multiple observations from PUNCH brought out the comet and its tail.

“We’re really pushing the limits of the system,” said Kevin Walsh, a planetary scientist at the Southwest Research Institute in Boulder, Colorado. Walsh led PUNCH’s observations of the comet. 

A round, white object appears to change slightly from frame to frame at the center of an animated GIF. Fuzzy, orange, parallel stripes of light streak from upper left to lower right in the background.
This movie shows PUNCH’s observations of comet 3I/ATLAS from Sept. 28 to Oct. 10, 2025, when the comet was between 231 million to 235 million miles from Earth. Each frame is a daily stacked image, made up of multiple observations taken of the comet each day. Stars create streaks of light in the background as the comet moves across the sky. The bright object that appears near the comet in a couple of frames is the planet Mars.
NASA/Southwest Research Institute

Comet 3I/ATLAS was discovered by the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope in Rio Hurtado, Chile, in July 2025. It is the third known object originating from outside our solar system discovered passing through our solar neighborhood.

While the comet poses no threat to Earth, multiple NASA spacecraft are studying it so scientists can learn as much as possible about this interstellar visitor before the comet leaves our solar system and heads back into interstellar space.

by Vanessa Thomas
NASA’s Goddard Space Flight Center, Greenbelt, Md.