In December 2025, the astronomical community is preparing for a rare event: the interstellar comet 3I/ATLAS will pass at its closest distance to our planet. Discovered in the summer of 2025 with ATLAS telescopes in Chile, this object has become only the third confirmed interstellar visitor to pass through the outskirts of our Solar System. Similar phenomena have only been observed twice before — in 2017 and 2019.
The trajectory of 3I/ATLAS shows that the comet came from the depths of interstellar space and will soon leave our system once again. At its closest approach, expected on December 19, the distance between the comet and Earth will be about 1.8 astronomical units — roughly 270 million kilometers. For comparison, that’s almost twice as far as the distance from Earth to the Sun.
Despite the vast distance, interest in this object is tremendous. The comet poses no threat to Earth or other planets, yet its appearance presents unique opportunities for scientific research. Astronomers around the world are preparing their equipment to capture even the smallest details of this icy wanderer’s behavior.
Interstellar traveler
3I/ATLAS is not just another comet. Its origin outside the Solar System makes it a true enigma for scientists. By analyzing the composition of the dust and gases that evaporate from the nucleus under the influence of the Sun’s heat, experts hope to gain new insights into how planets and comets form around other stars.
In recent weeks, interest in 3I/ATLAS has only increased. The European Space Agency (ESA) and other international organizations have already released the first images of the comet, captured by the Hubble telescope and the JUICE spacecraft, which is currently near Jupiter. These images have made it possible to examine the tail’s structure and estimate the object’s velocity.
Observation Opportunities
Although the comet will not be visible to the naked eye, astronomers and enthusiasts will be able to follow its movement online. A free live broadcast, organized by the Virtual Telescope project, will begin on December 18 at 11:00 p.m. EST (or 04:00 GMT on December 19). Lead astronomer Gianluca Masi promises to show viewers unique footage of the interstellar visitor’s flyby, weather permitting.
For professional observatories, this event is an opportunity to study the comet’s chemical composition and dynamics using spectroscopy and other methods. New scientific publications on the results of observations of 3I/ATLAS are expected in the coming weeks.
Scientific Significance
The appearance of interstellar objects within the Solar System is an extremely rare event. Each such visit provides a chance to test existing theories on the origin and evolution of comets, as well as on the processes occurring in other stellar systems. Scientists hope that the data collected will help to better understand how planetary systems form and what materials can be delivered to young planets from interstellar space.
Of particular interest is the comparison between 3I/ATLAS and previous interstellar objects — 1I/’Oumuamua and 2I/Borisov. Each possessed unique characteristics, and now researchers have the opportunity to expand our knowledge with yet another example.
In case you didn’t know, ATLAS (Asteroid Terrestrial-impact Last Alert System) is an international network of telescopes funded by NASA, designed for the early detection of asteroids and other celestial objects that could pose a threat to Earth. The system operates in Chile and Hawaii, providing round-the-clock sky monitoring. Thanks to ATLAS, dozens of new objects have been discovered, including the interstellar comet 3I/ATLAS, which became a true sensation among astronomers worldwide.
