An interstellar comet that originated outdoors our photo voltaic system has simply made its closest move to the solar, brightening dramatically and quickly because it did so. The explanation for the sudden excessive exercise is at present puzzling scientists.
A stranger within the neighborhood
The most recent customer to our nook of the galaxy was first noticed on July 1, 2025, by astronomers and formally named comet 3I/ATLAS. It is solely the third interstellar comet ever recorded and was calculated to be on a course that will take it near the solar with out plunging into it.
As the item neared its closest level to our star (perihelion), the immense photo voltaic glare made it nearly unattainable for Earth-based telescopes to see it. So astronomers turned to space-based photo voltaic observatories like SOHO, STEREO-A and GOES-19 to maintain a watchful eye.
In a paper printed on the arXiv preprint server, researchers confirmed that because the comet closed in on the solar, it was brightening at a steeply accelerating fee. This surge was extra excessive than had ever been noticed in a comet earlier than. These icy our bodies normally brighten slowly as they warmth up. The comet additionally appeared blue, which shocked scientists as comets are sometimes purple owing to mud reflecting daylight.
“Our cursory evaluation of this information signifies the comet will doubtless emerge from conjunction significantly brighter than when it entered, with an extrapolated geocentric V magnitude of ∼9 at perihelion, maybe pushed by outstanding, seen gasoline emission,” wrote the researchers of their paper.
Looking for solutions
Whereas the causes of the comet’s excessive conduct are puzzling, the examine’s authors suggest a number of potential causes. First, the brightening may have been attributable to an enormous surge of gasoline emanating from the comet. That is supported by the truth that the gasoline’s mild was blue and robust sufficient to overpower the mud’s reflection. The colour is a tell-tale signal of molecules like carbon glowing intensely when heated by the solar.
Another excuse could possibly be 3I/ATLAS’s distinctive composition. The researchers discovered that its chemical composition differs from that of comets in our photo voltaic system. For instance, there’s a greater carbon dioxide content material, extra unstable ices (which may clarify gasoline surges), and strange metals.
We might not have any definitive solutions but, however there shall be different alternatives to review this uncommon comet. Because it strikes away from the solar, ground-based telescopes can take over for extra detailed research.
Written for you by our writer Paul Arnold, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this text is the results of cautious human work. We depend on readers such as you to maintain impartial science journalism alive.
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Extra data:
Qicheng Zhang et al, Speedy Brightening of 3I/ATLAS Forward of Perihelion, arXiv (2025). DOI: 10.48550/arxiv.2510.25035
Journal data:
arXiv
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Speedy brightening of interstellar comet 3I/ATLAS because it nears solar surprises scientists (2025, October 31)
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