Astronomers Study Interstellar Comet 3I/ATLAS as It Passes Through Solar System

Astronomers are closely monitoring 3I/ATLAS, the third confirmed interstellar object to pass through our solar system, following 'Oumuamua in 2017 and Comet Borisov in 2019. Discovered on July 1, 2025, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Chile, 3I/ATLAS is currently traveling at approximately 137,000 miles per hour and is expected to reach its closest point to the Sun in late October.

Observations from NASA's Hubble Space Telescope and the James Webb Space Telescope (JWST) have provided detailed images and spectroscopic data of the comet. Hubble's images revealed a compact coma surrounding the nucleus, while JWST detected a coma dominated by carbon dioxide, with a CO2-to-water ratio among the highest ever observed in a comet.

The European Southern Observatory's Very Large Telescope (VLT) captured images showing the development of a classic cometary tail, indicating increasing activity as 3I/ATLAS approaches the Sun. Additionally, the Transiting Exoplanet Survey Satellite (TESS) provided precovery observations suggesting that the comet was active at a distance of approximately 6.4 astronomical units from the Sun, indicating early activity compared to typical comets.

3I/ATLAS is estimated to be between 7.6 and 14 billion years old, potentially making it older than our solar system. Its origin appears to be from the direction of the constellation Sagittarius, near the Milky Way's Galactic Center.

The comet will make its closest approach to Earth in mid-December 2025, passing at a safe distance of approximately 150 million miles. Astronomers continue to study 3I/ATLAS to gain insights into the composition and behavior of interstellar objects, enhancing our understanding of distant star systems and the early stages of planetary formation.