On the night of December 18–19, 2025, astronomers around the world are eagerly anticipating a rare event: the interstellar comet 3I/ATLAS will make its closest approach to Earth. Such visitors from other star systems are extremely rare in our Solar System, making this a unique occasion. This time, the comet will pass about 1.8 astronomical units from our planet—around 270 million kilometers—almost twice the distance from the Earth to the Sun.
Although 3I/ATLAS will not be a bright object in the night sky and won’t be visible to the naked eye, its flyby is of great interest to scientists. Opportunities to study matter formed in another star system are extremely rare. Astronomers are preparing telescopes and cameras to capture every moment of this flyby and gather as much data as possible about the composition and structure of the interstellar body.
Discovery history
Comet 3I/ATLAS was discovered on July 1, 2025, by the ATLAS automated telescopes, funded by NASA and located in Chile. It is only the third recorded interstellar object to visit our Solar System. Previously, astronomers observed the famous ‘Oumuamua’ in 2017 and comet 2I/Borisov in 2019.
Every such discovery sparks lively discussion in the scientific community. Interstellar objects carry information about processes occurring in other parts of the Galaxy. Studying them expands our understanding of how planetary systems form and the chemical makeup of the interstellar medium.
The Scientific Value of the Flyby
While 3I/ATLAS poses no threat to Earth, its flyby offers astronomers a unique opportunity to gather data. In the coming days, experts will use ground-based and space observatories to monitor the comet. Special attention is being given to analyzing its spectrum and the chemical composition of its tail, as well as the dynamics of its movement.
Interstellar comets differ from ordinary ones in that their material was formed outside our Solar System. This allows scientists to compare the properties of matter found in planets and comets around other stars with what we observe locally. Such comparisons may shed light on the processes of galactic evolution and the origins of organic compounds.
How to Observe the Event
A live online broadcast of the 3I/ATLAS flyby has been arranged for the general public. Anyone interested can tune in during the night of December 18-19, starting at 11:00 PM Eastern Time (or 04:00 GMT on December 19). A virtual telescope will provide a real-time view of the comet, weather permitting.
Astronomers recommend not missing the chance to witness this event online, as it may be a long time before another interstellar visitor appears. For professional researchers, this is an opportunity to conduct a series of observations that could help unravel the mysteries behind the origins of such objects.
If you didn’t know, the ATLAS project (Asteroid Terrestrial-impact Last Alert System) is an international network of automated telescopes designed for the early detection of asteroids and comets that could pose a potential threat to Earth. The system is funded by NASA and operates in different parts of the world, including Chile and Hawaii. Thanks to ATLAS, astronomers have already recorded several unique objects passing by our planet and continue to push the boundaries of our knowledge about space.
