Night Sky Tonight (Dec. 18, 2025): Watch Interstellar Comet 3I/ATLAS Live, Plus Moon–Mercury Dawn Pairing, Jupiter and Aurora Chances
Dec. 18, 2025 — If you’re planning to look up tonight, the sky has a rare mix of “big news” and easy wins. The headline event is an interstellar visitor—Comet 3I/ATLAS—making its closest pass by Earth (and getting a free livestream).