Interstellar comet 3I/ATLAS dramatically brightened after passing the Sun, with Harvard astrophysicist Avi Loeb warning it could be a hostile alien spacecraft whilst NASA’s SPHEREx telescope shows normal eruption
The mysterious space rock that journeyed through our solar system became notably brighter as it departed, scientists have revealed. Researchers observed that Comet 3I/ATLAS, which one Harvard astrophysicist suggested could be a hostile alien spacecraft, experienced a “dramatic increase in brightness” two months after the icy entity had reached its nearest point to the Sun.
This interstellar traveller, only the third of its kind to be detected in our solar system, sparked contentious theories upon its detection. Harvard astrophysicist Avi Loeb proposed that due to its peculiar glow, trajectory aligning with planetary orbits, and unnatural path, it could be an artificial alien probe on a reconnaissance mission.
A scientific paper co-authored by Loeb cautioned that the object might be a hostile spacecraft, for which humanity should brace itself. It stated: “The consequences, should the hypothesis turn out to be correct, could potentially be dire for humanity, and would possibly require defensive measures to be undertaken (though these might prove futile).”
NASA’s SPHEREx space telescope mission observed 3I/ATLAS in December 2025, when researchers theorised that the brightening was likely due to a phenomenon associated with comets as they release water, carbon dioxide, and carbon monoxide into space.
Study lead Carey Lisse, from Johns Hopkins Applied Physics Laboratory, commented: “Comet 3I/ATLAS was full-on erupting into space in December 2025, after its close flyby of the Sun, causing it to significantly brighten. The frozen water was rapidly transforming into vapour as it journeyed through the void between planets. Given that comets are roughly one-third water ice by volume, it was unleashing a wealth of fresh, carbon-laden matter that had been trapped beneath the surface for aeons.”
We are now seeing the usual range of early solar system materials, including organic molecules, soot, and rock dust, that are typically emitted by a comet.”
Yoonsoo Bach, deputy study lead from the Korea Astronomy and Space Science Institute, added: “Our unique space telescope is gathering unprecedented data from across the universe.
But in this case, our galaxy delivered a piece of a faraway star system to us only a few months after launch, and SPHEREx was ready to observe it. Science is sometimes like that: you’re in the right place at the right time.”
For the latest breaking news and stories from across the globe from the Daily Star, sign up for our newsletters.