Interstellar comet 3I/Atlas reappears without its tail after passing behind the Sun
Comet 3I/Atlas, an interstellar visitor from beyond our Solar System, has reappeared in the night sky after several weeks of disappearance.
However, astronomers were surprised to find that the comet was missing its characteristic glowing tail, raising new questions about what happened as it passed behind the Sun, News.Az reports, citing foreign media.
3I/Atlas, which was first spotted earlier this year, is only the third known interstellar comet to be discovered, following ‘Oumuamua in 2017 and 2I/Borisov in 2019. Scientists were initially excited to observe its fast movement, which indicated that it was not from our Solar System, but instead was passing through from another star system on its way out into deep space.
The comet passed behind the Sun in late October, reaching its perihelion, the point at which it came closest to the Sun. During this time, the Sun’s intense light made it impossible for Earth-based telescopes to observe. The heat and radiation from the Sun raised concerns among scientists, as many comets tend to break apart or lose their tails when they get too close to the Sun.
When 3I/Atlas became visible again, astronomers were quick to notice that it no longer had the bright, glowing tail that typically forms when a comet’s surface is heated by the Sun, causing ice and dust to evaporate. Experts speculate that the intense heat from the Sun might have caused the ice and gas that made up the tail to burn away, or perhaps the strong solar wind — streams of charged particles from the Sun — blew the tail away.
There is also a possibility that the tail still exists, but it’s facing away from Earth, making it invisible from our vantage point.
Additionally, as 3I/Atlas passed close to the Sun, ultraviolet (UV) rays from the Sun interacted with the comet’s gases, breaking down hydrocarbon molecules in the comet's atmosphere. This process creates diatomic carbon (C₂), which gives comets their faint greenish glow. A scientist compared this process to how UV rays cause sunburn on human skin, breaking apart molecular bonds in the comet’s gases.
The lack of a tail doesn’t diminish the importance of this comet’s appearance. In fact, it offers scientists a unique opportunity to learn more about objects from other star systems and to further understand how solar radiation can affect the appearance, structure, and composition of comets.
Now that 3I/Atlas is visible again, astronomers are carefully studying it with both ground-based and space telescopes. They aim to understand what the comet is made of, how it survived its close encounter with the Sun, and what its journey might reveal about the formation of stars and planets in other parts of the galaxy.
Even without its tail, 3I/Atlas remains a significant discovery, offering scientists a rare glimpse into the nature of interstellar objects and the dynamics of space beyond our Solar System. As the comet continues its journey away from the Sun, researchers will keep a close watch, hoping to uncover more secrets about this fascinating interstellar traveler.
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