Data Confirms Interstellar Object 3I/ATLAS Brightened Rapidly Behind the Sun as NASA Spacecraft Tracks Historic Visitor

One study suggests 3I/ATLAS is around 3 billion years older than our 4.6 billion-year-old solar system. The object is also likely the largest interstellar object ever seen, with Hubble Space Telescope data suggesting 3I/ATLAS has a maximum width of about 3.5 miles.

Comet 3I/ATLAS poses no threat to Earth and will remain far away, with its closest approach to our planet at about 1.8 astronomical units (approximately 170 million miles) on December 19, 2025. The comet reached its closest point to the Sun around October 30 at a distance of about 1.4 astronomical units (130 million miles)—just inside the orbit of Mars.

From October 30 to November 6, Europa Clipper will potentially be immersed within the ion tail of 3I/ATLAS, providing the opportunity to detect the signatures of an interstellar comet’s ion tail. Spacecraft Hera will possibly be immersed within the ion tail of 3I/ATLAS from October 25 to November 1.

WHAT’S NEXT

The object will become visible again to Earth-based telescopes by early December, and may even be visible to spacecraft orbiting Jupiter as it makes a close approach to the gas giant in March 2026. Throughout its run, 3I/ATLAS is expected to fade from around 11th magnitude in mid-November to 12.5 by the 30th, then another 2 magnitudes by the end of December. The object will remain observable through December 2025 as it moves through the constellations Virgo and Leo before continuing its journey out of the solar system.