Comet 3I/ATLAS — one of just three known interstellar objects — makes its closest approach to Earth in the early hours of December 19. It will pass safely at about 168 million miles (270 million km) and is estimated to be between 320 meters and 5.6 kilometers across, traveling roughly 130,000 mph. The comet won’t be visible to the naked eye; use a telescope or follow a live stream from the Virtual Telescope Project. Observers should consult sky apps and local viewing conditions for the best chance to spot it.
Interstellar Comet 3I/ATLAS Near Earth Tonight — How to See It
Interstellar comet 3I/ATLAS streaks across the sky with a blue plasma tail, photographed from June Lake, California, on December 14, 2025.Dan Bartlett
One of only three known interstellar objects ever detected, comet 3I/ATLAS is making a single pass through our solar system and will make its closest approach to Earth in the early hours of December 19. Below is everything you need to know to try to spot this rare visitor.
What Is 3I/ATLAS?
3I/ATLAS is a comet — a mixture of ice, dust and frozen gases often called a “cosmic snowball.” Unlike most comets that originate in the Kuiper Belt or Oort Cloud inside our solar system, 3I/ATLAS formed around another star and is just passing through. After this flyby it will continue on its way and never return.
Key Facts
Discovery: First spotted in June 2025 in images taken by the ATLAS survey telescope in Rio Hurtado, Chile; discovery announced July 1.
Size: Estimated between about 1,000 feet (320 meters) and 3.5 miles (5.6 kilometers).
Speed: Traveling roughly 130,000 miles per hour (about 209,000 km/h).
Closest approach: Around 1 a.m. EST (6 a.m. GMT) on December 19, when it will be roughly 168 million miles (270 million kilometers) from Earth — nearly twice the distance between Earth and the Sun. There is no risk of impact.
How To See It Tonight
3I/ATLAS is not bright enough to be seen with the unaided eye or with weak binoculars. Your best chance is through a telescope — either your own backyard scope or one at a local observatory. Skywatching and astronomy apps can help you pinpoint its exact position and track its motion across the sky.
Currently the comet is located in the constellation Leo, not far from the bright star Regulus. Visibility at the exact time of closest approach depends on your location: observers on the U.S. East Coast, for example, will find it highest in the pre-dawn sky.
Live Stream
If you can’t observe the comet locally, the Virtual Telescope Project will host a live stream with observations from telescopes in Manciano, Italy. The broadcast is scheduled to begin at 11 p.m. EST on December 18 (4:00 GMT on December 19), weather permitting.
Why Astronomers Care
Because 3I/ATLAS originated around another star, studying it gives astronomers a rare opportunity to examine material formed in a different planetary system. Multiple observatories and space agencies worldwide have already trained instruments on the comet to learn about its composition, structure and behavior during the flyby.
Observation Tip: Check local observing conditions, moon phase and use star-chart apps to schedule a viewing window when the comet is highest and the sky is darkest.
If you want more technical updates or images, follow reputable astronomy outlets and observatories for real-time results from professional telescopes.
