Astronomers and space enthusiasts are abuzz over 3I/ATLAS, a newly discovered interstellar comet that has entered the Solar System, only the third confirmed visitor from beyond our cosmic neighbourhood. Spotted in July 2025 by NASA’s Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Chile, the comet has quickly become the focus of international fascination.
The arrival of 3I/ATLAS marks another rare moment in astronomy, following the discoveries of ʻOumuamua in 2017 and 2I/Borisov in 2019. All three are thought to be comet-like objects ejected from other planetary systems, offering scientists extraordinary insights into how planets form and evolve elsewhere in the galaxy.
Unlike ʻOumuamua, whose mysterious, cigar-shaped body once fuelled theories of alien technology, 3I/ATLAS is unmistakably a true comet. It features a solid icy nucleus roughly one kilometre wide, making it larger than Borisov and visible through professional telescopes as it streaks through the inner Solar System.
A Comet With a Twist
What has truly intrigued scientists, however, is 3I/ATLAS’s “backwards” tail. Most comets develop tails that extend away from the Sun, driven by the pressure of solar radiation. In this case, though, astronomers have observed a secondary stream of large, heavy dust particles appearing to flow towards the Sun.
Researchers explain that these grains are too heavy to be blown away by solar energy and are instead pushed outward by the comet’s own internal gas emissions, which intensify as it heats up. This unique phenomenon gives the comet its striking, reversed appearance.
As 3I/ATLAS makes its closest pass to the Sun later this month, scientists worldwide are racing to study it in detail, hoping to uncover new secrets about interstellar chemistry and the forces shaping these cosmic wanderers.
