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.

Two weeks ago, it was hidden behind the Sun, far out of sight. Last week, it reached perihelion, the closest point it will ever get to the Sun. Now, Comet 3I/ATLAS is back and this time, it can be seen from Earth.

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.

A truly once-in-a-generation event is unfolding! Interstellar Comet 3I/ATLAS is now visible from Earth after its journey behind the Sun.

"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.