NASA Confirms 3I/ATLAS as Natural Interstellar Comet in Latest Observations

August 26, 2025 - Today, space agencies and astronomy teams released new data revealing the true nature of 3I/ATLAS, the third known interstellar visitor to enter our Solar System.

In a joint announcement, NASA’s SPHEREx mission and the James Webb Space Telescope (JWST) presented infrared measurements and spectroscopic analyses demonstrating that 3I/ATLAS is a bona fide comet, not an alien spacecraft or artificial object. SPHEREx observations captured strong absorption features from solid water-ice alongside a massive carbon dioxide coma, while JWST’s Near-Infrared Spectrograph detected definitive emission lines of CO₂, trace carbon monoxide, and low-level water-ice signatures at 3.2 AU from the Sun. These findings explain the comet’s unusual brightness and dispel earlier speculations of nuclear-powered propulsion.

High-resolution imagery from the Hubble Space Telescope, complemented by JWST’s data, constrained the nucleus radius to approximately 2.7 km-significantly smaller than initial estimates of 10-30 km, which conflated nucleus and coma light. The hyperbolic trajectory (eccentricity > 6) confirms its interstellar origin, tracing back to the Milky Way’s thick disk where older star systems reside.

NASA and ESA scientists emphasised that all observed coma and tail features arise from solar heating and natural outgassing processes. Despite public commentary suggesting extraterrestrial technology, the spectral profile and coma morphology match known cometary behavior. Moving safely beyond 1.8 AU from Earth, 3I/ATLAS poses no threat and will remain visible through September before solar conjunction obscures it until December.

These coordinated observations offer an unprecedented glimpse into pristine material from beyond our Solar System, providing clues about planetary formation in other star systems. Continuous monitoring by ground- and space-based observatories will further refine our understanding of this remarkable interstellar visitor.