3I/ATLAS: New interstellar comet discovered in the solar system

A new interstellar object has appeared in our solar system. The ATLAS telescope in Chile, designed primarily to monitor asteroids, discovered it on July 1. The US space agency NASA believes it is a comet from the constellation Sagittarius. It was officially named 3I/ATLAS.

It is only the third object discovered that researchers have been able to confirm origins outside our solar system. "The fact that we see some blurriness suggests that it's mostly ice and not rock," Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, told the French news agency AFP. This suggests a comet rather than an asteroid.

"We suspect that these little ice balls probably form in association with star systems," McDowell explained. "And then when another star passes by, it pulls on the ice ball and releases it. It spins out of control, wandering through the galaxy, and now this one is passing right by us."

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3I/ATLAS is currently approximately 670 million kilometers from Earth—roughly as far away as Jupiter. With an estimated diameter of 10 to 20 kilometers, it would be the largest interstellar interloper ever discovered. However, astronomers still disagree on its exact size.

Particularly striking is the speed at which the comet is racing through the solar system. It's more than 60 kilometers per second. For researchers, this indicates that 3I/ATLAS, unlike comets and asteroids, which all form within our solar system, is not bound to the sun's orbit. This also means that it originated in interstellar space—and will return there.

NASA clarifies that there is no danger to Earth. The comet will remain at a distance of approximately 240 million kilometers. Astronomers can observe it with ground-based telescopes until September. After that, it will be too close to the Sun to be observed. The next opportunity to see 3I/ATLAS will not be until early December, when it reappears on the far side of the Sun.

Space researchers discovered the first interstellar object, 'Oumuamua, in 2017. At one point, there was suspicion that it might be an alien spacecraft. However, this theory was quickly refuted. Instead, it was likely an asteroid or comet. The second interstellar invader was comet 2I/Borisov, spotted in 2019.

Models estimate that up to 10,000 interstellar objects are drifting through the solar system. However, most are so small that they are undetectable by telescopes. With the Vera C. Rubin Observatory launched in Chile, which houses the largest digital camera ever built, experts believe these objects could be detected more frequently in the future.

The Vera C. Rubin Observatory takes high-resolution images of the Southern Hemisphere night sky.

Source: H. Stockebrand/NSF-DOE Vera C.R

"Interstellar objects visiting the solar system are the only way to directly observe objects from other star systems," says Michael Küppers, project scientist for the Comet Interceptor mission of the European Space Agency (ESA). "Studying their composition or physical properties, for example, provides us with insights into the conditions under which other planetary systems form, which we can compare with the solar system. Interestingly, the interstellar objects reaching us appear to be more diverse than we thought."

But studying these objects is a challenge. "Even more information could be obtained with a space mission on such an object," Küppers continues. "However, this is difficult because the objects are discovered relatively shortly before their flyby. The only chance would be to have a mission ready and either launch it when a suitable object is found or park the mission in space."