Recent astronomical observations of Comet 3I/ATLAS have commenced following its reappearance after passing behind the Sun, an event known as perihelion, which occurred on October 29. Astronomer Qicheng Zhang reportedly captured new images revealing a prominent green glow emanating from the comet. This distinct hue is attributed to the detection of diatomic carbon (C2) particles, which naturally fluoresce green when observed through a specific filter.
Prior to its solar passage, the comet was noted for a bluer appearance. A study co-authored by Zhang, released to the preprint server arXiv on October 28, indicated that 3I/ATLAS experienced rapid brightening and was distinctly bluer ahead of perihelion. The current green coloration observed in the new images does not definitively suggest a color alteration *after* perihelion, but rather that a change might have occurred beforehand. Additionally, while images may suggest an absence of a dust tail, reports clarify that a tail is indeed present but is being observed largely head-on, contributing to its subtle, asymmetric visual effect.
Source: https://www.livemint.com/news/world/3iatlas-interstellar-comet-glows-green-in-new-image-astronomer-links-it-to-sunscreen-11762570434632.html