Third Confirmed Interstellar Object Observed Passing Through Solar System

Discovery of Interstellar Object

An image from the Saguaro Observatory shows interstellar object A11pI3Z, captured on June 2, 2025, by David Rankin of the Catalina Sky Survey at the University of Arizona.

Astronomers have confirmed the discovery of an interstellar object passing through the solar system. This is the third such object observed, and scientists consider it likely that additional objects may pass by without detection.

The object, designated 3I/Atlas, is likely the largest interstellar object detected to date and has been classified as a comet.

Peter Veres, an astronomer with the International Astronomical Union's Minor Planet Center, stated:

"It looks kind of fuzzy. It seems that there is some gas around it, and I think one or two telescopes reported a very short tail."

Initially known as A11pl3Z before its interstellar origin was confirmed, the object does not pose a threat to Earth, according to Richard Moissl, head of planetary defense at the European Space Agency.

"It will fly deep through the solar system, passing just inside the orbit of Mars," Moissl said. It is not expected to impact Mars.

Astronomers are refining their calculations, but current estimates indicate the object is traveling at over 60 kilometers (37 miles) per second. This speed suggests it is not gravitationally bound to the Sun, distinguishing it from objects that remain within the solar system.

Moissl added:

"Its trajectory means it's not orbiting our star, but coming from interstellar space and flying off to there again."

Formation and Discovery

Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, explained:

"We think that probably these little ice balls get formed associated with star systems. And then as another star passes by, tugs on the ice ball, frees it out. It goes rogue, wanders through the galaxy, and now this one is just passing us."

The object was first identified by a Chile-based observatory that is part of the NASA-funded ATLAS survey. Subsequently, astronomers worldwide reviewed previous telescope data, tracing its trajectory back to at least June 14.

According to Moissl, the object is currently estimated to be approximately 10-20 kilometers wide, making it the largest interstellar object detected so far. However, if the object is composed primarily of ice, which reflects more light, it could be smaller than estimated.

Veres noted that the object will become brighter as it approaches the Sun, with its path bending slightly due to gravity. It is expected to reach its closest point to the Sun (perihelion) on October 29. After this, it will move away and exit the solar system over the next few years.

Previous Interstellar Objects

This is the third time an object from outside the solar system has been detected entering it.

• The first, 'Oumuamua, was discovered in 2017.
• The second, 2I/Borisov, was observed in 2019.

There is currently no evidence to suggest an artificial origin for 3I/Atlas. Research teams are investigating its shape, composition, and rotation.

Mark Norris, an astronomer at the University of Central Lancashire, stated that the new object appears to be moving faster than the previously discovered interstellar objects. He noted that the object is currently at a distance from Earth similar to that of Jupiter.

Norris referenced models estimating that as many as 10,000 interstellar objects may be present in the solar system at any time, though most would be smaller than 3I/Atlas. If accurate, the Vera C. Rubin Observatory in Chile may detect such objects more frequently in the future.

Moissl indicated that launching a mission to intercept the object is not currently feasible. However, these interstellar objects provide opportunities to study material from outside the solar system.

For example, Norris noted that detecting precursors of life, such as amino acids, on such objects could provide evidence that conditions for life exist in other star systems.