When it comes to cosmic oddities, it seems like everyone's eyes are on one object right now: Comet 3I/ATLAS. The mysterious comet, with its blue-green glow and dusty tail, has sparked endless questions since its first discovery in July 2025.
Astronomers and space enthusiasts have speculated about this visitor's original home in our solar system; some people have even taken advantage of the hype about Comet 3I/ATLAS to add stories that it may be associated with extraterrestrial life.
In short, there is no evidence that Comet 3I/ATLAS was a spacecraft piloted by aliens, a far-fetched theory that scientists are trying to disprove. But what is true identity of comet 3I/ATLAS? Find out what scientists have learned so far about the interstellar object, from its origins to its chemical composition.
Read more: When was Halley's Comet last seen and will it ever return?
Guest of our Solar System
NASA's Swift Ultraviolet/Optical Telescope (UVOT) observed interstellar comet 3I/ATLAS during two visits in July and August 2025. The panels show visible light (left) and ultraviolet (right) images in which the faint glow of hydroxyl (OH) tracks water vapor escaping from the comet. Each image includes dozens of short, three-minute exposures, carefully composed so that the total integration time is about 42 minutes in visible light and 2.3 hours in ultraviolet. Swift's vantage point above Earth's atmosphere allowed astronomers to detect these ultraviolet emissions that are normally invisible from the ground.
(Image credit: Dennis Bodewits, Auburn University)
On July 1, 2025, the Asteroid Last Alert System (ATLAS) Survey Telescope in Chile caught a glimpse of something entering the inner solar system at 137,000 mph. This was the very first observation of Comet 3I/ATLAS.
The hyperbolic shape of the comet's orbital path confirmed that it is not gravitationally bound to the Sun, meaning it will pass directly through the Solar System before continuing its journey into deep space. This also prompted scientists to claim that Comet 3I/ATLAS is only the third interstellar object ever recorded, hence the “3I” in its name (the “I” stands for “interstellar”).
On October 30, 2025, the comet reached perihelion, or its closest approach to the Sun, at an altitude of 210 million kilometers.
Colorful cloud and tail
Like other comets, Comet 3I/ATLAS has a core of solid ice and a bright blanket of gas and dust formed into a long tail. Its icy core is estimated to be between 3.5 miles (5.6 kilometers) and 1,000 feet (320 meters) in diameter, although scientists are working to better understand its true size, according to the study. V Letters in an astrophysical journal.
It was observed that the gas and dust surrounding it formed a cloud called a “coma”, which grew as it approached the Sun. This is normal for others comets who pass by the sun; As they approach the glowing heat of a star, the frozen gases on their surface sublimate, that is, they change from a physical state to a gaseous state without melting into a liquid.
Comet 3I/ATLAS's blue-green tail is also growing; this is because the solar wind pushes it back into the coma, causing gas and dust to trail behind it.
There are several additional features of Comet 3I/ATLAS that set it apart from other comets. The most obvious is that it has some unknown origin beyond our solar system. Only two other objects with interstellar origin observed: 1I/'Oumuamua in 2017 and 2I/Borisov in 2019.
However, Comet 3I/ATLAS took a different path than the previous two interstellar objects. Its trajectory appears much steeper and faster, which also indicates that the comet may have emerged from the Milky Way's “fat disk” – a collection of stars orbiting above and below the thin plane where the Sun lies.
According to a study conducted in Royal Astronomical Society. While non-interstellar comets can be as old as 4.5 billion years, Comet 3I/ATLAS may be several billion years older.
Why Comet3I/Atlas is important
Astronomers also paid attention to the composition of the comet – its coma emits an unusually large amount of carbon dioxide gas, but it also contains carbon monoxide (CO). They also discovered water on the comet thanks to its ultraviolet radiation byproduct, hydroxyl (OH), which can absorb radiation. A comet's water content may indicate how interstellar comets form and how the building blocks of life outside the solar system are formed.
Recently, the South African Radio Astronomy Observatory radio telescope detected a radio signal from a comet based on radio absorption by hydroxyl radicals. This establishes without a doubt that Comet 3I/ATLAS is a natural comet and nothing else.
According to the European Space Agency, the comet will approach Earth on December 19, 2025, at a distance of 270 million kilometers from our planet. But rest assured: we are not in any danger. The comet would later fly past Jupiter in March 2026 and eventually leave the solar system to continue its journey. Until then, astronomers will be keeping a close eye on Comet 3I/ATLAS in hopes of discovering what other clues it might hold about deep space.
Read more: Could alien life travel on interstellar asteroids and comets like 'Oumuamua?
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