Trick or treat: Here's where to find comets Lemmon, SWAN and 3I/ATLAS in the Halloween sky

A bright comet is pictured against a black starry sky with its bright central coma visible to the lower left of the image from which a bright tail extends to the upper left.

Halloween is upon us and the 2025 spooky season is abuzz with talk of three cosmic visitors — Comet Lemmon, Comet SWAN and the interstellar traveler 3I ATLAS — said to be haunting the night sky. But when it comes to stargazing, one of these ghostly wanderers is more trick than treat!

Comets are composed of primordial matter left over from the creation of our solar system — and others — which become active as they approach the sun, as the increase in heat radiation causes icy materials to transform into a gaseous shell around the nucleus. That shell is then blown away by the solar wind — the relentless stream of charged particles issuing forth from our star — creating a tail that reflects sunlight..