Interstellar comet 3I/ATLAS makes closest approach to Earth before Christmas

The interstellar comet 3I/ATLAS is set to make its closest approach to Earth on December 19, 2025. Astronomers are looking forward to this event, anticipating it as a unique Christmas-time observation opportunity.

3I/ATLAS is only the third interstellar object that has been confirmed. The other two were 'Oumuamua, spotted in 2017, and comet 2I/Borisov, observed in 2019.

Discovery of 3I/ATLAS

The Asteroid Terrestrial-impact Last Alert System (ATLAS), a NASA-funded survey telescope located in Rio Hurtado, Chile, initially reported the sighting of the interstellar comet on July 1, 2025. The comet, arriving from the direction of the constellation Sagittarius, was officially designated 3I/ATLAS.

Initially identified as A11pl3Z, ground-based telescopes were able to observe 3I/ATLAS until September 2025. In October 2025, it passed its closest point to the Sun. The Hubble Space Telescope, using its Wide Field Camera 3, re-observed 3I/ATLAS on November 30, 2025.

Closest Approach to Earth

NASA has announced that December 19, 2025, marks the date when 3I/ATLAS will be at its closest proximity to Earth, just six days before Christmas. Space.com reports that this will be the closest this "erratic wanderer" will ever be to our planet.

Skywatchers equipped with a small telescope or powerful binoculars will have the chance to view the comet up close. Observations from Hubble have enabled astronomers to refine their estimations of the comet's solid, icy nucleus size. Researchers have determined that the nucleus has an upper limit of 3.5 miles (5.6 kilometers) in diameter, but it could potentially be as small as 1,000 feet (320 meters) across.

The comet's close Earth approach presents a valuable opportunity for astronomers to study planet formation in other solar systems and compare those processes with what occurred in our own.