NASA Reveals First Data on Interstellar Comet 3I/ATLAS — A Rare Visitor Racing Through Our Solar System

Interstellar comet 3I/ATLAS is racing through the inner solar system this month, giving astronomers a rare, front-row seat to study material forged beyond our Sun’s influence. The icy visitor made its closest pass by the Sun on October 30 and is now heading for a December 19 fly-by that will bring it within about 167 million miles (270 million kilometres) of Earth—safely on the far side of the Sun but bright enough for professional telescopes to continue imaging. Discovered on 1 July 2025 by the NASA-funded ATLAS survey in Chile, 3I/ATLAS is only the third confirmed interstellar object ever detected after 1I/‘Oumuamua and 2I/Borisov. Its hyperbolic orbit proves it originated outside our solar system, making every observation a window into the chemistry of another star’s planetary leftovers. NASA’S MULTI-MISSION CAMPAIGN NASA quickly organized a fleet-wide observing campaign. The Hubble Space Telescope captured a detailed portrait on 30 November, revealing a teardrop-shaped coma and twin tails of dust and plasma. Earlier near-infrared spectra from the James Webb Space Telescope traced carbon monoxide and carbon dioxide streaming off the nucleus, helping scientists constrain its diameter to no more than 3.5 miles (5.6 km). Even spacecraft en route to other worlds are pitching in. ESA’s Jupiter Icy Moons Explorer (Juice) snapped the comet from 41 million miles away, while NASA’s Psyche probe, Lucy Trojan-asteroid mission, Mars Reconnaissance Orbiter, MAVEN and the Perseverance rover have all logged images or ultraviolet data. These multiple vantage points are mapping changes in the coma as sunlight drives off ices, revealing how interstellar comets differ—or closely resemble—their solar-system cousins. WHY 3I/ATLAS MATTERS • Pristine materials: Because 3I/ATLAS formed around another star, its ices record a different recipe of volatiles that can refine models of planetary formation across the galaxy. • Natural lab test: Comparing its activity to 2I/Borisov lets researchers probe how heliophysics processes—solar wind, magnetic fields and radiation—affect foreign objects. • Future defense: Understanding trajectories like 3I/ATLAS helps calibrate planetary-defense software for tracking any inbound objects, interstellar or not. OBSERVING OUTLOOK Ground-based astronomers have until late January to catch the comet before it dims below large-telescope limits. Although its peak magnitude will stay around 15—too faint for backyard scopes—online tools such as NASA’s Eyes on the Solar System let the public follow its path in real time. After swinging past Earth’s orbit, 3I/ATLAS will slingshot back into interstellar space, never to return. Data from Juice, Webb and Hubble will continue streaming down through early 2026, promising new insights into the temperatures, isotopes and dust grain sizes locked inside this cosmic messenger. As astronomers mine that treasure trove, 3I/ATLAS will fade into the deep, but the secrets it leaves behind could illuminate how many other star systems cook up comets—and, by extension, planets like our own.