Interstellar Comet Atlas Makes Close Approach to Earth Before Returning to Interstellar Space

A stray comet from another star is swinging past Earth this week in one last hurrah before racing back toward interstellar space. Discovered over the summer, the comet known as 3I/Atlas will pass within 167 million miles (269 million kilometers) of our planet on Friday, the closest it gets on its grand tour of the solar system. NASA continues to aim its space telescopes at the visiting ice ball, estimated to be between 1,444 feet (440 meters) and 3.5 miles (5.6 kilometers) in size. It is fading as it exits, so now is the time for backyard astronomers to catch it in the night sky with their telescopes. The comet will come much closer to Jupiter in March, zipping within 33 million miles (53 million kilometers).

It will take until the mid-2030s before 3I/Atlas leaves the solar system entirely and heads back toward interstellar space, never to return, said Paul Chodas, director of NASA’s Center for Near Earth Object Studies. It’s the third known interstellar object to cut through our solar system. Interstellar comets originate in star systems elsewhere in the Milky Way, while home-grown comets like Halley hail from the icy fringes of our solar system. A telescope in Hawaii discovered the first confirmed interstellar visitor in 2017. Two years later, an interstellar comet was spotted by a Crimean amateur astronomer. NASA’s sky-surveying Atlas telescope in Chile spotted comet 3I/Atlas in July while prowling for potentially dangerous asteroids. Scientists believe the latest interloping comet may have originated in a star system much older than ours, making it a tantalizing target.

Discovered by the Atlas survey in Chile, the object marks only the third known interstellar visitor to cross our solar system. Its path and speed will help researchers study material that formed around other stars, offering a rare real-time glimpse of a planetary system different from our own. While 3I/Atlas is not expected to pose any threat to Earth, the encounter highlights the ongoing value of solar system surveys that alert scientists to distant visitors as they pass through the inner solar system.

As it sails outward, 3I/Atlas will approach Jupiter in March. It will then travel through the outer solar system and continue on toward interstellar space, a process that will stretch into the mid-2030s before the object reaches the galaxy’s edge from our vantage point. The event serves as a reminder that the solar system is not an isolated island but rather part of a broader Milky Way where stars exchange material via passing comets.

For amateur stargazers, the moment is fleeting but possible. With the object fading, a modest telescope under dark skies can reveal a faint point moving against the backdrop of stars. The news also underscores the ongoing importance of sky surveys that keep watch for near Earth threats while cataloging objects that offer scientific opportunities to study distant star systems.