Interstellar Comet 3I/Atlas Recorded Earlier Than Thought, and Was Already Active

KOMPAS.com – An interesting revelation comes from the NASA data archive. The Transiting Exoplanet Survey Satellite (TESS) search telescope apparently had a chance to record the presence of comet 3I/Atlas two months before the rare object was officially announced. This fact concurrently opens a new insight into the unique nature of interstellar visitors.

Comet 3I/Atlas was first announced in early July 2025. Though,recent research shows that this object was recorded by TESS as early May. Even more surprising, the older data shows signs that this comet was “active” long before it was discovered.

“This finding confirms how meaningful telescope data records are,” wrote the researchers led by Adina Feinstein and Darryl Seligman from Michigan State University, together with John Noonan from Auburn University.

How TESS Captured the Fast-Moving Comet

It’s important to note that TESS is not designed to find faint objects such as interstellar comets. Its main mission is to observe radiant stars and detect planets outside the solar system (exoplanets) by measuring dips in starlight when a planet passes in front of it.

However, because the area of the sky monitored by TESS was also crossed by 3I/atlas, scientists attempted to find its tracks. The technique used is called “shift-stacking”: they predict the position of the comet in each image, then shift the image so that the object is at the same point, and finally stack the images. As a result, the faint signal of the comet was successfully detected.