Today, December 19, 2025, Earth is receiving a rare visit from another star system. The interstellar comet known as 3I/ATLAS has just made its closest approach to our planet, passing within 168 million miles (270 million kilometers) .
This event marks a unique opportunity to connect with a voyager that has drifted between the stars for possibly billions of years, and it will be our one and only chance to see it.
A Rare Interstellar Visitor
Comet 3I/ATLAS is only the third known object from outside our solar system to be discovered passing through our celestial neighborhood, following 1I/’Oumuamua in 2017 and 2I/Borisov in 2019 . It is a frozen remnant from the planetary formation process around another, unknown star. After a close encounter with a giant planet in its home system, it was ejected into the dark of interstellar space, where it drifted until its path happened to intersect with ours .
Scientists determined its interstellar origin because it is moving too fast to be captured by the Sun’s gravity. It follows what’s called a hyperbolic trajectory—it is simply passing through our solar system on a one-way trip . After it departs, it will never return.
Why Today is So Important for Science
For astronomers, today’s close approach is an “early Christmas gift” . As the comet nears Earth, telescopes can gather more detailed data about its composition. Early observations from powerful instruments like the James Webb Space Telescope have already revealed that 3I/ATLAS is unusually rich in carbon dioxide . Analyzing its ices and dust provides a direct sample of the building blocks of planets from another star system, offering invaluable insights into how our own cosmic backyard compares to others in the galaxy .
How to Watch the Comet Tonight
While the moment of absolute closest approach occurred earlier today at 1 a.m. EST (0600 GMT), the comet remains visible and will be the focus of a special observation tonight .
Option 1: Tune into the Global Livestream (The Easiest & Most Reliable Method)
The premier way to see the comet is via a free, online livestream. Astrophysicist Gianluca Masi of Italy’s Virtual Telescope Project had planned to broadcast the comet’s close approach live. However, due to rain at the observation site, the event has been rescheduled for tonight, December 19, at 11 p.m. EST (0400 GMT on December 20) .
- What to do: You can watch the livestream by visiting the Virtual Telescope Project website at the scheduled time.
Option 2: Try to Spot It Yourself with a Telescope
If you have access to a telescope, you can attempt to find the comet in the night sky. Be warned: it will not be visible to the naked eye or standard binoculars .
- What you need: A moderate to large backyard telescope is necessary to see it as a faint, fuzzy spot.
- Where to look: The comet is currently located in the constellation Leo. It will be highest in the pre-dawn eastern sky, but as of tonight, it will be visible in the evening as well .
- Use a guide: To pinpoint its exact location, use a reliable astronomy app like SkySafari or the NASA’s Eyes on the Solar System interactive simulation .
Key Facts About Comet 3I/ATLAS
A Legacy of Discovery
This comet’s fleeting visit has been a major event for the world’s space agencies. NASA has mobilized a fleet of missions to observe it, including the Hubble and James Webb Space Telescopes, the Perseverance rover on Mars, and even the Europa Clipper spacecraft, which is still on its journey to Jupiter . Each observation adds a piece to the puzzle of this interstellar traveler’s story.
Tonight offers a final, focused chance for the public to witness this historic object. Whether you join the global watch party via the Virtual Telescope Project livestream or point your own telescope toward Leo, you’ll be witnessing a truly exceptional event—the departure of a visitor from the depths of interstellar space, never to be seen again.