Comet 3I/ATLAS is a rare interstellar visitor, a comet not gravitationally bound to any star, and only the third such object ever identified.
When discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey in Rio Hurtado, Chile, on 1 July 2025, it was 670 million km from the Sun, technically within the inner Solar System.
Its closest approach to Earth, 270 million km or 1.8 AU, was on 19 December 2025.
Perihelion occurred on 29 October, 203 million km or 1.36 AU from the Sun.
Thought to originate from a region of the Milky Way populated by older stars, 3I/ATLAS may be over 7 billion years old – older than our Solar System.
As far as amateur observations go, it’s a tricky object due to its low brightness.
On 1 January 2026, comet 3I/ATLAS is expected to be at mag. +15.6, best suited to imaging setups.
Although faint, it’s within reach of smaller smart telescopes. In late December, 3I/ATLAS was near the bright star Regulus (Alpha (α) Leonis), following a westward path towards Cancer.
On 1 January, it lies approximately 2.5° north of mag. +3.5 Omicron (ο) Leonis, around 20° above the eastern horizon at 22:00 UT, reaching 52° altitude when due south at 03:00 UT.
It passes just under 4° north of mag. +6.9 M67 on the nights of 11/12 and 12/13 January, when it could be mag. +16.0.
On 16 January, at mag. +16.3, it passes 3.5° south of M44. Towards the end of the month, it’s not far from Jupiter.
If you manage to spot or photograph comet 3I/ATLAS in January 2026, let us know by emailing contactus@skyatnightmagazine.com
