Interstellar Comet 3I/ATLAS | Vera C. Rubin Observatory—LSST Camera
The faint coma and tail glow of comet 3I/ATLAS were captured by the National Science Foundation–Department of Energy Vera C. Rubin Observatory, jointly funded by the U.S. National Science Foundation (NSF) and the U.S. Department of Energy's Office of Science (DOE/SC), on December 19, 2025. Comet 3I/ATLAS is only the third known visitor from another star system to pass through our Solar System. The comet reappeared from behind the Sun in November 2025 after spending several weeks out of view from Earth. By the time of this observation, the object was at its closest point to Earth on its outward journey toward interstellar space. Rubin incidentally imaged this object months earlier during testing activities, before it was identified as an interstellar comet.
What makes this NOIRLab image special is the amount of detail captured in a single 30-second exposure. Usually, revealing the faint glow of a comet’s tail requires a much longer exposure—one that would show the background stars and galaxies as blurry streaks. However, Rubin’s light-collecting power and highly sensitive LSST Camera capture the comet’s delicate tail in just 30 seconds while keeping the distant background objects crisp and clear.
Objects like 3I/ATLAS are rare and scientifically valuable. Unlike the common comets and asteroids that formed alongside our Sun, interstellar objects were formed in other planetary systems. At a point in their distant past, they were ejected from their home systems by gravitational interactions. After being cast out, these objects travel through interstellar space, occasionally passing through another planetary system like our own. When they appear in our neighborhood, they give scientists a rare opportunity to study material formed around other stars—assuming we can catch a glimpse of them while they are close by.
This is where the Rubin Observatory shines. Unlike telescopes that focus on individual targets or small regions of space, Rubin is a survey telescope that repeatedly scans large portions of the sky. With its extremely wide field of view and ability to detect very faint light sources, Rubin catches dim, moving objects that might otherwise go unnoticed. Additionally, Rubin sends out an alert for every change it detects, so scientists can be on the lookout for unusual objects moving through our Solar System.
With Rubin data, researchers expect to discover many more interstellar visitors passing through our neighborhood, each carrying clues about the processes that shape planets and small bodies around other stars. Studying these objects in greater numbers will help scientists better understand how planetary systems, including our own, form and evolve.
NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA
Acknowledgement: C. O. Chandler (University of Washington)
Image Date: Dec. 19, 2025
Release Date: July 15, 2026
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