Newly spotted comet is third interstellar object seen in our solar system

3I/Atlas is located about 420mn miles from Earth, travelling at a speed of around 60kph away from the centre of the Milky Way

This undated diagram shows the trajectory of the interstellar comet 3I/ATLAS as it passes through the solar system, released by NASA on July 2, 2025. NASA/JPL-Caltech

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 US space agency NASA, the interloper - named 3I/ATLAS - was first spotted on Tuesday 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 37 miles (60 km) per second from the direction of the center of the Milky Way galaxy, 3I/ATLAS is presently located about 420 million miles (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, co-principal investigator for ATLAS, said on Thursday.

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 km (6.2 miles) 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 150 million miles (240 million km) away, equivalent to more than 1-1/2 times the distance between Earth and the sun. It is currently located about 416 million miles (670 million km) from the sun and will reach its closest approach to the sun around October 30, when it will be about 130 million miles (210 million km) 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.