Have you heard about ThreeI Atlas, the comet that’s rewriting the record books? I recently came across stunning Hubble images revealing this interstellar visitor, first spotted by the Atlas telescope in July 2025. What makes it unforgettable is that it is the fastest comet ever recorded, speeding through our solar system at an astonishing 130,000 mph (209,000 km/h). Unlike most comets bound by the sun’s gravity, ThreeI Atlas is on a hyperbolic trajectory, meaning it’s just passing through — then it will disappear forever into the depths of interstellar space.
This blazing traveler isn’t just fast; it’s incredibly rare. It’s only the third confirmed interstellar object we’ve seen in our solar backyard, following 1I ‘Oumuamua in 2017 and 2I Borisov in 2019. But ThreeI Atlas differs in remarkable ways, showing classic comet features like a bright coma and a developing tail, all caught in crisp detail by Hubble’s high-resolution images.
A comet with a cosmic origin story
One of the most fascinating things about ThreeI Atlas is that its nucleus, the solid core, is cloaked by a glowing cloud of gas and dust known as the coma. Thanks to those Hubble snapshots, scientists have estimated its size to be somewhere between 1,000 feet (320 meters) and 3.5 miles (5.6 km) across, which is smaller than some of our famous comets like Hale-Bopp. But size isn’t the main draw here — it’s what the comet is made of.
As it heats up from the sun, its icy nucleus releases gas and dust in a process called sublimation, creating that iconic glowing coma and tail we associate with comets. Water vapor detected in the coma confirms it behaves like typical solar system comets in this sense. But what’s truly exciting is that this comet carries materials and molecules from outside our solar system. Carbon-based molecules and complex organics found in the coma could provide clues about the chemistry of other star systems, substances we rarely get to examine up close.
ThreeI Atlas is a rare cosmic messenger, offering a peek into the building blocks of planets and stars beyond our solar system.
Window into interstellar space during closest approach
Mark October 29, 2025, on your cosmic calendar — that’s when ThreeI Atlas will reach perihelion, its closest point to the sun, about 1.36 AU away (around 167 million miles), roughly between Earth and Mars. Although it won’t come closer than 1.88 AU to Earth, astronomers will be closely tracking its activity as it heats up, intensifies sublimation, and releases even more gases.
This period is a golden opportunity to gather spectroscopic data and decode the comet’s chemical composition, comparing it with those born inside our solar system. After perihelion, ThreeI Atlas will continue its lonely journey outward, fading from our view but still visible briefly from Mars, before vanishing forever into interstellar space.
Its hyper-speed means we’ll likely not see many interstellar comets like this anytime soon. Yet, predictions suggest that thousands of such visitors might be passing through our solar system in any given moment, though most are too small or dim for current instruments. Future observatories, like the Vera C Rubin Observatory in Chile, could change this by regularly spotting these rare travelers.
Why ThreeI Atlas matters
ThreeI Atlas isn’t just another glowing streak in the night sky. It’s a rare window into the composition and origins of other star systems, a cosmic traveler carrying secrets from deep space. Its visit enriches our understanding of how solar systems form and evolve. And importantly, it highlights our growing ability to detect and study such interstellar wanderers before they vanish into the dark void.
Watching something fly through our solar system that was born light years away challenges our perspective on the vastness and connections of the cosmos. It’s moments like these that remind us how much there is still to explore and learn.
So, next time you look up at the sky, remember that among the stars might be visitors just like ThreeI Atlas — fleeting, fast, and full of cosmic stories to tell.