Astronomers have verified the existence of an unusual interstellar object traveling through our solar system, the third such occurrence ever observed. Scientists estimate numerous other such objects are likely to go undetected.
Dubbed 3I/Atlas by the International Astronomical Union’s Minor Planet Center, the object has been officially named a comet and may be the largest interstellar visitor ever spotted, based on a report filed by Science Alert.
Jonathan McDowell, an astronomer at Harvard-Smithsonian Center for Astrophysics, explained, “The fact that we see some fuzziness suggests that it is mostly ice rather than mostly rock.”
It was first picked up as A11pl3Z before it got its new name when its interstellar status was confirmed. European Space Agency planetary defense expert Richard Moissl ensured that it does not threaten Earth. “It will pass deep within the Solar System, just inside Mars’ orbit,” he explained, “but will not strike our neighbour planet.”
Moving at an unprecedented velocity of around 37 miles per second, this comet is free from the gravitational hold of the Sun. Moissl elucidated, “It’s not orbiting our star, but coming from interstellar space and flying off to there again.”
McDowell continued to explain how such objects come into existence: “We believe that likely these small iceballs form with star systems. And then another star comes by, pulls on the iceball, releases it out. It becomes rogue, drifts around in the galaxy, and now this one is just cruising by.
The comet was initially observed by the Hawaii-based NASA-funded ATLAS survey last Tuesday. The discovery was confirmed by astronomer David Rankin on Bluesky. Researchers then searched through archived data and discovered its tail dating back to mid-June.
Moissl made the comet possibly between 10 and 20 kilometers wide, although it would be smaller if it was composed mostly of ice, which scatters more light. “It will become brighter and nearer to the Sun until late October and then still visible (telescopic) until next year,” he said.
Mark Norris, an astronomer at the University of Central Lancashire, noted that this comet is “traveling much more quickly than the other two extra-solar objects we previously identified.” Currently, it’s about as far from Earth as Jupiter, but “it is only currently visible from the Southern Hemisphere,” which means Norris cannot see it on that night.
Norris also said that models estimate there may be as many as 10,000 interstellar objects in the solar system at any given moment, although most of them are too small to see. With new telescopes such as the Vera C. Rubin Observatory in Chile going into operation, many more of these objects may be detected soon.
Even with this, Moissl stated that sending a mission to intercept this comet is not possible. However, astronomers keep looking. Norris said that finding evidence of life, in the form of amino acids, on any of these comets would be a deep discovery. “A lot more confidence that the conditions for life exist in other star systems,” he said.
This comet is one of two other known interstellar guests to our solar system: ‘Oumuamua in 2017, which ignited and later discredited alien rumors, and 2I/Borisov in 2019.