NASA's Hubble Space Telescope has captured the clearest image yet of 3I/ATLAS, an unexpected interstellar comet currently racing through our solar system at a breathtaking speed of 130,000 miles per hour. This marks the third interstellar object ever discovered, and Hubble’s ultra-crisp imagery is helping scientists pin down vital clues about its origin, size, and behavior.
The comet, first spotted by the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System) on July 1, 2025, was discovered at a distance of 420 million miles from the Sun. Although it poses no threat to Earth, it offers a rare chance to study material that originated in a completely different star system somewhere in the Milky Way galaxy.
What Hubble Revealed
Using its advanced optics, Hubble observed a sunlit dust plume erupting from the comet’s surface and captured the beginnings of a dust tail streaming away from the nucleus. Based on the data, astronomers now estimate the comet’s solid, icy core — its nucleus — could be up to 3.5 miles (5.6 km) in diameter, or as small as 1,000 feet (320 meters). However, the nucleus itself remains invisible, even to Hubble, due to the enveloping coma and dust.
The comet’s dust-loss rate also matches that of typical solar system comets observed around 300 million miles from the Sun, suggesting a surprisingly familiar behavior — except for its alien origin.
A Visitor from Beyond
“This interstellar visitor originated in some other solar system elsewhere in our galaxy,” NASA noted. Its extreme velocity and trajectory suggest it has spent billions of years drifting through space, picking up momentum from gravitational interactions with countless stars and nebulae before entering our solar system.
“No one knows where the comet came from,” said David Jewitt, lead scientist for the Hubble observations from UCLA. “It’s like glimpsing a rifle bullet for a thousandth of a second. You can't project that back with any accuracy to figure out where it started on its path.”
The discovery contributes to growing evidence of a hidden population of interstellar visitors—space relics that have long wandered the galaxy but are only now becoming detectable thanks to powerful sky surveys.
A New Era of Interstellar Discoveries
“This latest interstellar tourist is one of a previously undetected population of objects bursting onto the scene,” Jewitt added. “This is now possible because we have powerful sky survey capabilities that we didn't have before. We've crossed a threshold.”
NASA’s James Webb Space Telescope, TESS, Neil Gehrels Swift Observatory, and the W.M. Keck Observatory are also scheduled to observe 3I/ATLAS, helping scientists unravel the comet’s chemical composition and refine their understanding of its physical properties.
3I/ATLAS will remain visible to ground-based telescopes through September 2025, after which it will pass too close to the Sun to observe. It is expected to reappear by early December, offering another window into its mysterious journey through space.
A paper detailing these early Hubble findings will be published in The Astrophysical Journal Letters, and is currently available on Astro-ph.
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