The object, first detected in July, is only the third known interstellar comet ever observed. Its reemergence marks the first opportunity for optical imaging since it became obscured by solar glare during its close pass to the sun in late October.

Could a comet be concealing an engine? That is the question now hovering over 3I/ATLAS, the third confirmed interstellar object to pass through our Solar System, after scientists detected a non‑gravitational acceleration and a striking blue coloration near its closest approach to the Sun.

Most comets are white, yellow, blue, and occasionally green-but a rare golden comet is now gracing the sky. Dubbed C/2025 K1 (ATLAS), the icy visitor was discovered in May 2025 by the Asteroid Terrestrial-impact Last Alert System.

Mystery deepens as 3I/ATLAS deviates near the Sun

This first optical post-perihelion image of comet 3I/ATLAS gave astronomers a rare glimpse into the behavior and composition of one of the most unusual visitors ever to pass through our solar system.

I/ATLAS showed signs of non-gravitational acceleration as it passed near the sun, attracting global scientific attention. Harvard Institute’s Avi Loeb spoke with NBC News’ Gadi Schwartz to discuss these new discoveries.

"This might also explain the report on 3I/ATLAS getting 'bluer than Sun.'" "It could potentially be explained by a hot engine or source of artificial light," he wrote, adding that it could also be a natural signature of a comet.