Newly Spotted Comet Is 3rd Interstellar Object Seen in Solar System

Reuters

15:51 JST, July 20, 2025

WASHINGTON (Reuters) — Astronomers are tracking a newly spotted comet hailing from parts unknown, only the third time such an interstellar object has been observed visiting our solar system.

According to U.S. space agency NASA, the interloper — named 3I/ATLAS — was first spotted on July 1 by an Asteroid Terrestrial-impact Last Alert System, or ATLAS, telescope located in Rio Hurtado, Chile. Astronomers said its unusual trajectory indicated it had ventured from beyond our solar system.

Journeying at a speed of around 60 kilometers per second from the direction of the center of the Milky Way galaxy, 3I/ATLAS is presently located about 670 million kilometers from Earth.

“Beyond that we do not know very much, and there are many efforts underway to observe this object with larger telescopes to determine composition,” University of Hawaii astronomer Larry Denneau, coprincipal investigator for ATLAS, said on July 3.

The only other such interstellar visitors previously observed by astronomers were objects called 1I/’Oumuamua (pronounced oh-MOO-uh-MOO-uh), detected in 2017, and 2I/Borisov, discovered in 2019.

“The comet has some similarities to 2I/Borisov in that it appears to be an icy comet, but it is much larger, possibly 10 kilometers in diameter,” Denneau said.

“It currently has a faint coma,” Denneau added, referring to the cloud of gas and dust surrounding a comet’s nucleus, “but the coma and tail may increase dramatically as the object comes closer to the sun. Its closest approach to the sun will be later this year, when it will come inside the orbit of Mars. We don’t know what will happen, so that’s exciting.”

Astronomers said the comet poses no threat to Earth and will never come closer than 240 million kilometers away, equivalent to more than 1½ times the distance between Earth and the sun. It is currently located about 670 million kilometers from the sun and will reach its closest approach to the sun around Oct. 30, when it will be about 210 million kilometers away from our star.

The ATLAS network is a NASA-funded telescope survey built and operated by the University of Hawaii, with five telescopes around the world that scan the night sky continuously to look for objects that could threaten Earth.