The interstellar comet 3I/ATLAS reached its closest point to Earth early Friday, December 19, marking a scientifically important moment for astronomers studying visitors from beyond our solar system. While the comet remained far too distant to pose any threat to Earth, researchers were able to pinpoint the exact moment of its nearest approach.

Based on precise orbital calculations from NASA’s Jet Propulsion Laboratory (JPL) Horizons system, comet 3I/ATLAS made its closest pass at 1 a.m. EST (0600 GMT) on December 19. At that time, the comet was approximately 1.8 astronomical units away from Earth—about 168 million miles (270 million kilometers). This distance is nearly twice the average separation between Earth and the sun.

A Rare Interstellar Visitor

Comet 3I/ATLAS was first discovered on July 1 by NASA-funded ATLAS telescopes in Chile. It is only the third confirmed interstellar object ever observed traveling through our solar system. The first was ʻOumuamua, detected in 2017, followed by 2I/Borisov in 2019.

What makes 3I/ATLAS especially intriguing is its origin. Unlike comets that form within our own solar system, interstellar objects originate around other stars and are ejected into interstellar space before occasionally passing through systems like ours.

Scientific Value Over Visual Spectacle

Although 3I/ATLAS will not become visible to the naked eye due to its distance and faintness, its passage is extremely valuable for science. Interstellar objects are exceedingly rare, and each one offers a unique opportunity to study material formed in another planetary system.

Observing 3I/ATLAS near its closest approach allows astronomers to analyze its composition, behavior, and structure, helping scientists better understand how planetary systems form and evolve across the galaxy.

How to Watch the Flyby Online

Skywatchers can still take part in the event virtually. A live webcast of comet 3I/ATLAS is being hosted by the Virtual Telescope Project, in partnership with Space.com, on December 19–20.

The livestream begins at 11 p.m. EST on December 19 (0400 GMT on December 20) and will provide real-time views of the comet as it passes near Earth, weather conditions permitting.

Those interested can also stay updated with ongoing coverage and analysis through Space.com’s live blog, which continues to track the interstellar visitor’s journey through the solar system.