4 ways to track 3I/ATLAS without a telescope as it makes its closest approach to Earth tonight

Interstellar comet 3I/ATLAS makes its closest approach to Earth on Dec. 19. Here's how you can track its progress both during the pass and as it races out of the solar system on its way to interstellar space, never to be seen again.

3I/ATLAS was discovered on July 1 earlier this year by astronomers using the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey telescopes, which scan the night sky in search of moving objects that could one day pose a threat to Earth.

An analysis of 3I/ATLAS's movement quickly confirmed it to be just the third visitor to our solar system that was created in the orbit of an alien star, after the 2017 comet 'Oumuamua and 2I/Borisov, which buzzed the sun in 2019.

3I/ATLAS came closest to the sun on Oct. 31, when it advanced within 130 million miles (210 kilometers) from our parent star. At its closest approach to Earth — which will occur at 1 a.m. EST (0600 MGT) on Dec. 19 — the interstellar visitor will still be separated by a mind-boggling 170 million miles (273 million km) from our Blue Marble.

As such, the interstellar invader won't be visible to the naked eye, though a 12-inch (30 centimeter) telescope may allow you to spot it as a point of light travelling through a patch of sky below the stars of the constellation Leo on the night of Dec. 19, according to NASA.

Naturally, the vast majority of stargazers won't get to see 3I/ATLAS bid farewell to Earth with their own eyes. Instead, these handy resources — and a livestream — can be used to track the interstellar visitor during its flyby and in the weeks that follow, as it gradually disappears from our view forever.

NASA Eyes on the Solar System.

Follow along with 3I/ATLAS's trajectory using NASA's Eyes on the Solar System, which uses data and imagery from agency missions to create a sophisticated 3D model of the sun's domain, which visualizes the orbits of planets, moons and spacecraft, along with wandering asteroids and comets.

Simply click on the magnifying glass icon in the upper right and search "3I/ATLAS" to see the interstellar invader's path. On Dec. 19 the comet will be travelling beyond the orbit of Mars ahead of a flyby of the gas giant Jupiter on March 12, 2026.

You can also scroll backwards and forwards through time and select to replay close planetary passes using the intuitive on-screen options to see all the highlights of 3I/ATLAS's journey through the solar system.

Track 3I/ATLAS's brightness using the the Comet Observation Database

You can track the average brightness of 3I/ATLAS and other solar system objects using the Comet Observation Database (COBS), courtesy of the Crni Vrh Observatory in Slovenia.

COBS accepts data submissions from amateur astronomers and plots the observations to show how a comet's lightcurve — or brightness as perceived from Earth — has varied over time. As expected, 3I/ATLAS's brightness has dipped significantly following its closest approach to the sun on Oct. 29, as it travels further from the warming influence and light of our parent star.

Virtual Telescope Project Livestream

Hoping to catch a glimpse of 3I/ATLAS on Dec. 19, but don't own a monster telescope capable of spotting it? Then be sure to tune into the Virtual Telescope Project's free YouTube livestream of the event starting at 11 p.m. EST pm Dec. 18 (0400 GMT on Dec. 19), which will feature real-time images of the comet captured by robotic telescopes located in Manciano, Italy.

Track its position using a smartphone astronomy app

While it may not be visible to most telescopes, you can still track the patch of sky containing 3I/ATLAS in the constellation Leo using a trusted smartphone astronomy app such as Stellarium, which uses augmented reality tech to help you find its position in the night sky.

Are you looking to upgrade your skywatching equipment? Then be sure to check out our picks of the best binoculars and telescopes for exploring the post-sunset realm in 2025 and beyond.