Hubble Captures Sharpest Image of Interstellar Comet 3I/ATLAS

Astronomers have obtained the clearest image yet of the interstellar comet 3I/ATLAS, thanks to the capabilities of NASA’s Hubble Space Telescope. This comet, originating from outside our solar system, has captivated scientists as it journeys through our celestial neighborhood.

Discovery and Initial Observations

Comet 3I/ATLAS was first detected on July 1, 2025, by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) at a distance of 420 million miles from the Sun. NASA is tracking the comet with a fleet of space telescopes to gather data on its size and physical properties.

Comet Size and Composition

Hubble’s observations have helped astronomers estimate the size of the comet’s solid icy nucleus. The upper limit on the diameter is 5.6 kilometers (3.5 miles), though it could be as small as 320 meters (1,000 feet). While the nucleus itself remains difficult to observe directly, Hubble captured a dust plume ejected from the sun-warmed side of the comet and a faint dust tail.

Unprecedented Speed and Trajectory

3I/ATLAS is traveling at approximately 210,000 kilometers per hour (130,000 miles per hour), the highest velocity ever recorded for a visitor to our solar system. This speed suggests the comet has been drifting through interstellar space for billions of years, gaining momentum from the gravitational influence of stars and nebulae.

Similarities to Solar System Comets

The comet’s dust loss rate is consistent with comets originating within our solar system, despite its interstellar origins. This suggests similar processes are at play in the formation and behavior of comets regardless of their origin.

Ongoing Observations

Hubble reobserved 3I/ATLAS on November 30, 2025, capturing images as the comet moved across the sky. Other NASA missions, including the James Webb Space Telescope, are also contributing to the study of 3I/ATLAS, aiming to refine our understanding of its chemical makeup. The comet is expected to remain visible to ground-based telescopes until September, after which it will pass too close to the Sun to be observed, and is expected to reappear on the other side of the Sun in early December.

A Window into Other Solar Systems

“This latest interstellar tourist is one of a population of previously undetected objects that have suddenly appeared and will be gradually revealed,” said David Jewitt of the University of California, Los Angeles, science team leader for the Hubble observations. The increasing capabilities of sky survey telescopes are allowing astronomers to identify more of these interstellar visitors, offering a unique opportunity to study objects from other solar systems.