As it slips back into deep space, the interstellar comet 3I/ATLAS is behaving in ways that defy expectations. Instead of fading quietly, the rogue object has erupted with a vast X-ray glow and fresh jets of gas and dust, revealing a complex interior that is only now waking up to the Sun’s past heat. The latest observations from a NASA space telescope capture this bizarre late-stage activity in unprecedented detail, turning a dim outbound visitor into one of the most revealing natural experiments in the sky.
For planetary scientists, the spectacle is more than a curiosity. 3I/ATLAS is only the third known object to barrel through our solar system from another star, and its evolving outburst offers a rare look at material that may predate the Sun itself. By tracking how its coma and tail respond as it exits, researchers are effectively watching an alien world shed layers of history in real time.
The strange X-ray flare lighting up 3I/ATLAS
The most striking new twist in 3I/ATLAS’s story is the discovery of a vast X-ray halo surrounding the comet as it heads outward. Scientists report that the glow stretches some 250,000 miles into space, a scale that rivals the distance from Earth to the Moon. I see that as a clear sign that the comet is still actively interacting with the solar wind, even as it races away from the planets that first revealed it.
What makes this flare so unusual is its timing. The comet has already swung past its closest approach to the Sun, yet the X-ray emission has intensified well after that point, suggesting that buried ices are only now responding to the heat that seeped inward earlier in its journey. According to Scientists, this delayed ignition hints at a layered interior where volatile materials are insulated until the Sun’s energy penetrates deep enough to trigger a secondary wave of activity.
A rare alignment gives Hubble a front-row seat
To understand how that activity looks in visible light, astronomers took advantage of a rare geometric coincidence earlier this year. During a brief window, Earth passed almost directly between the Sun and the comet, placing 3I/ATLAS near opposition and dramatically boosting its apparent brightness. That lineup allowed the Hubble Space Telescope to capture a close look at the object when our planet sat nearly in line with the Sun and the comet, turning a distant speck into a richly detailed target.
Those images build on earlier Hubble work that already showed 3I/ATLAS sporting an exceptionally long tail, streaming with volatile material reacting to sunlight. When Hubble captured it in July 2025, astronomers noted that the object was unlike any interstellar visitor seen before, with a tail that stretched far beyond early estimates and reshaped what we thought we knew about such travelers. That earlier view of the Astronomers’ “breathtaking” tail now meshes with the X-ray halo, painting a picture of a comet that is bleeding material across multiple wavelengths as it departs.
What makes 3I/ATLAS such an unusual interstellar relic
Part of the fascination with 3I/ATLAS comes from its origin story. Observations of the comet’s trajectory show that it is not gravitationally bound to the Sun, confirming that it is only the third known object to pass through our solar system from outside, after 1I/ʻOumuamua and 2I/Borisov. NASA scientists have compiled detailed Facts and FAQS on the object, emphasizing that its hyperbolic path and speed mark it as a true interstellar comet rather than a long-period visitor from our own distant Oort Cloud.
Researchers suspect that this Comet may be a frozen relic from before the Sun formed, preserving chemistry from a different stellar nursery. One study argues that 3I/ATLAS could be the most ancient visitor ever detected, potentially older than our solar system itself, and therefore a unique probe of how other planetary systems assemble. That perspective is grounded in models of how such bodies are ejected from their birth systems and supported by early spectral data, which suggest that ATLAS carries ices and dust that have remained largely unaltered for billions of years.
How NASA’s telescopes are dissecting the comet’s coma
To decode that ancient material, NASA has thrown some of its most powerful observatories at 3I/ATLAS. The James Webb Space Telescope used its Near-Infrared Spectrograph to study the comet on Aug. 6, revealing a rich coma packed with complex molecules. In internal reports, NASA scientists describe a “Rich Coma” around the nucleus, with Webb’s sensitivity allowing them to tease out subtle signatures that hint at the comet’s formation environment and thermal history.
Another key player is SPHEREx, the Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ice Explorer, which is designed to map the sky in infrared light. As part of its mission, Spectro surveys will repeatedly scan comets, including interstellar ones, to build a statistical picture of their ices. In targeted imaging of 3I/ATLAS, NASA’s SPHEREx team has examined the structure of the coma, using detectors and optics built by industrial partners to capture how gas and dust flow away from the nucleus. Those observations, described in a recent Description, are crucial for linking the X-ray halo to the underlying outgassing that feeds it.
From green glow to giant jets: a changing portrait
Ground-based telescopes have added their own surprises to the mix. The Gemini North telescope captured a striking color image of 3I/ATLAS in late 2025, revealing a strange green glow around the nucleus that traces emissions from excited molecules in the coma. That view, taken with careful tracking to keep the stars in place while the comet moved, showed how the object’s color and structure evolved as it passed near the Sun, and underscored how dynamic the coma had become.
More recent reports describe giant jets blasting from the surface, carving asymmetries into the tail and hinting at localized vents that switch on as different regions rotate into sunlight. Analysts following the object have framed 3I/ATLAS as a “rare visionary” interstellar comet whose odd behaviour keeps forcing modelers back to the drawing board. One detailed explainer on Interstellar Comet 3I/ATLAS highlights how each new image, from jets to color shifts, has revealed another layer of complexity in the way this nucleus sheds material.
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*This article was researched with the help of AI, with human editors creating the final content.
