Comet 3I/ATLAS, discovered by NASA astronomers in July, has once again attracted international attention after the release of a recent image showing a sudden and completely unexpected change in its structure. Classified as the third interstellar object to enter our solar system, after Oumuamua (2017) and 2I/Borisov (2019), ATLAS continues to surprise scientists with its unusual behavior.
- See pictures: NASA releases the first images of interstellar comet 3I/ATLAS
- Capture in pictures: The images show that the tail of interstellar comet 3I/ATLAS has grown by three million kilometres
Although experts insist that there is no risk of colliding with Earth, as its closest point will be about 270 million kilometers away, the series of anomalies discovered sparked a wave of studies and discussions in the astronomical community.
First warning: an “anti-tail” pointing toward the sun
This was the phenomenon that first attracted attention and was recorded shortly after its discovery. Unlike traditional comets, which appear to have their tails pointed away from the Sun due to the solar wind, 3I/ATLAS features an antitail, which is a stream of material directed toward the star.
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According to DW, this structure consists of an unusual mixture of carbon dioxide, water, traces of cyanide and a nickel alloy never seen before in natural processes, similar to what is produced by human industrial activity. Astronomers who observed the object using the Northern Optical Telescope in the Canary Islands described its behavior as “strange” and “difficult to explain using current models.”
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The second alarm: the disappearance of his strange tail
The anomaly reached a new level on November 5, 2025, when NASA released images that revealed the anti-tail had disappeared, and in its place a broad, luminous conventional tail appeared. This tail is estimated to exceed 56,000 km today, driven by a mass loss of about 13% after perihelion and anomalous acceleration inconsistent with typical comet outgassing.
The Hubble and James Webb Space Telescopes (JWST) have discovered other phenomena that have raised suspicions:
- It is believed that the noticeable change in the comet’s color, which now has blue tones, is related to ionized carbon monoxide.
- An extreme level of polarization in the reflected light, a behavior unprecedented in comets studied to date.
- Sudden changes in the activity of its core, contradicting sublimation models that explain the behavior of other icy bodies.
These patterns have prompted many scientific teams to rethink hypotheses about the formation, origin and dynamics of this type of interstellar visitor.
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Does this comet pose any danger to Earth?
According to NASA, the comet does not pose any threat to Earth. “The 3I/ATLAS pass will occur at a distance of hundreds of millions of kilometers and poses no threat to human life or terrestrial infrastructure,” they stated. However, experts agree that it represents an exceptional scientific opportunity to continue studying celestial bodies in this solar system and others.
Finally, what’s really amazing is that anyone, anywhere on Earth, can observe it with a telescope. That’s why many enthusiasts have started sharing photos of their sightings on social media.