Astronomers have recorded a rare phenomenon: an interstellar comet in the Solar System

The object, designated 3I/Atlas, was spotted on 2 July 2025 and has been classified as a comet, Phys.org writes.

According to Peter Veresch, an astronomer at the International Centre for Minor Planets, the object "looks slightly blurry" and is probably surrounded by a cloud of gas. Some telescopes have even detected a short tail, suggesting it belongs to the class of "cosmic snowballs."

The size of 3I/Atlas, according to preliminary data, is between 10 and 20 kilometres, making it the largest of all interstellar bodies discovered by mankind. As explained Richard Moissl, head of the planetary defence division of the European Space Agency (ESA), the object poses no threat to Earth and will fly "inside the orbit of Mars" without colliding with it.

Astronomers emphasise: the object is travelling at speeds of more than 60 km/s, well above the speeds of typical solar system bodies and means it is not gravitationally bound to the Sun.

"It's not just another comet," Moissl explains. - 'It's not orbiting our luminary, it came from interstellar space and it's going to go there, too.

According to astrophysicist Jonathan McDowell of the Harvard-Smithsonian Centre, such icy bodies probably form in other star systems and are ejected into space when other stars pass nearby.

"They become space travellers, and right now one of them is flying past us," the scientist said.

The object was first spotted at an observatory in Chile participating in the ATLAS project (funded by NASA). Astronomers around the world then checked archived data from telescopes and tracked its path until at least 14 June.

Perihelion (maximum approach to the Sun) is expected to occur on 29 October, after which the object will begin to leave the solar system.

3I/Atlas is the third interstellar visitor spotted by mankind. The first was the mysterious 'Oumuamua in 2017, which, due to its unusual shape, sparked speculation of a possible artificial origin. The second was comet 2I/Borisov, discovered in 2019.

At the moment, there is no reason to believe that 3I/Atlas is artificially created. Nevertheless, scientists around the world are rushing to study its shape, chemical composition and rotational speed.

Astronomer Mark Norris of the University of Central Lancashire said the object is "travelling much faster than previous interstellar bodies we have observed". It is now about the distance of Jupiter from Earth.

Modelling shows that as many as 10,000 similar objects could be passing through the solar system at any given moment, it's just that most of them are too small or faint to notice. The new Vera C. Rubin in Chile may soon begin recording such phenomena every month.

Although launching an interceptor mission to 3I/Atlas is impossible because of its speed and distance, scientists emphasise: such visitors are a rare opportunity to study matter formed outside our star system.

As Norris notes, "if precursors of life, such as amino acids, are found on such objects, it will greatly increase our chances of detecting life in other star systems as well".