The Hubble Space Telescope has provided its most detailed images to date of interstellar comet 3I/ATLAS, offering a rare look at a visitor from beyond our solar system. Discovered on July 1, 2025, by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS), this celestial object is the third known interstellar body to pass through our cosmic neighborhood, following 'Oumuamua and Comet Borisov.
Traveling at speeds exceeding 130,000 miles per hour, 3I/ATLAS is on a hyperbolic trajectory, confirming its origin outside our solar system. The comet is expected to reach its closest approach to the Sun on October 30, 2025, passing inside the orbit of Mars. It poses no threat to Earth, maintaining a safe distance of at least 150 million miles. Hubble's advanced imaging capabilities have allowed astronomers to refine estimates of the comet's nucleus size, suggesting a diameter between 1,000 feet and 3.5 miles, potentially making 3I/ATLAS the largest interstellar object observed to date.
The comet's activity, including the ejection of dust plumes and the formation of a faint tail, is consistent with comets originating within our solar system, even at its current distance from the Sun. Spectroscopic analysis has detected water vapor and hydroxide ions, indicating active sublimation of water ice, which is unusual so far from the Sun. Further analysis suggests 3I/ATLAS may be an ancient relic, potentially over 7 billion years old, predating our own solar system. Its journey through the galaxy, shaped by billions of years of gravitational interactions, has imparted immense speed, a testament to its long voyage. The comet's composition, rich in water ice and possibly organic compounds, offers a unique opportunity to study the building blocks of planetary systems in other star systems. Astronomers will continue to monitor 3I/ATLAS as it continues its journey, with observations expected to provide further insights into its composition and the conditions of its home star system. The comet is anticipated to reappear on the other side of the Sun by early December 2025, allowing for continued study.