Comet 3I/Atlas, the rare interstellar traveler that made headlines earlier this year, has reappeared in the night sky after several weeks of being hidden behind the Sun. However, scientists have observed a significant change — the comet, which once sported a brilliant glowing tail, now appears without it.
This unexpected transformation has raised new questions about the comet’s journey and its survival after a close pass by the Sun.
3I/Atlas is no ordinary comet. It’s the third interstellar object ever discovered, following ‘Oumuamua in 2017 and 2I/Borisov in 2019. What makes 3I/Atlas especially intriguing is that it came from outside our Solar System, passing through from another star system before continuing its journey back into deep space.
Its discovery earlier this year sparked excitement among astronomers because of its unusual speed and trajectory, confirming that it was not a native object of our Solar System.
In late October, the comet passed closest to the Sun, reaching a point called perihelion. During this period, the Sun’s intense brightness and radiation made it impossible for Earth-based telescopes to observe the comet.
Scientists were concerned that the extreme heat could cause the comet to disintegrate, as many comets do when they venture too close to the Sun.
Now that 3I/Atlas has reemerged from behind the Sun, astronomers are perplexed by the comet’s changed appearance. Normally, a comet’s tail forms as solar radiation melts the ice and dust on its surface, creating a glowing trail.
However, when 3I/Atlas became visible again, its once-bright tail was completely absent. Experts believe that the Sun’s heat could have caused the ice and gas making up the tail to vaporize, or the powerful solar wind — a stream of charged particles — may have blown it off into space.
There is also a possibility that the tail still exists but is simply not visible from Earth. The comet’s tail could be pointing away from our view, which would make it invisible from our perspective on Earth.
Another key change scientists have noted is that ultraviolet (UV) rays from the Sun began breaking down large hydrocarbon molecules in the comet’s atmosphere. This process has led to the formation of diatomic carbon (C₂), a gas responsible for the faint greenish glow often associated with comets.
A scientist explained the phenomenon: “It’s similar to how our skin gets sunburned by UV rays. The UV light breaks apart molecular bonds — in this case, within the comet’s gases.”
This provides valuable insight into how sunlight can alter a comet’s physical characteristics, including its color, brightness, and shape, as it travels through space. While 3I/Atlas may not have the same dazzling tail it once did, its journey remains a fascinating subject for study.
Researchers are continuing to observe 3I/Atlas carefully with both ground-based and space telescopes to learn more about its composition and how it survived the intense heat of its solar encounter.
Because the comet originates from another star system, it offers a rare opportunity to study how stars and planets form in other parts of the galaxy.
Despite the loss of its tail, 3I/Atlas remains an important and exciting discovery for astronomers. As the comet moves farther away from the Sun and continues its long trek through space, scientists will keep monitoring its path to gain deeper insights into the nature of interstellar objects and the mysteries of our cosmic neighborhood.
