Comet 3I/ATLAS, the third known visitor from beyond our Solar System, is brightening rapidly as it approaches perihelion, its closest point to the Sun.
Due to its position behind the Sun, ground-based observations have been nearly impossible, but solar-monitoring satellites have been used to track the comet.
Researchers Qicheng Zhang and Karl Battams used instruments aboard STEREO-A, SOHO, and GOES-19 to capture the comet's transformation.
Related: Strange Green Glow From Interstellar Comet 3I/ATLAS Has Scientists Puzzled
Astronomers are surprised by the comet's blue shine, with further observations needed to understand this phenomenon.
Author's summary: Comet 3I/ATLAS surprises astronomers with rapid brightening.