Astronomers say one of the rarest comets ever observed, the mysterious 3I/ATLAS, likely isn’t alone, and that more mysterious interstellar visitors to our solar system could soon be on the way.
Such discoveries are likely, even though 3I/ATLAS is only the third confirmed interstellar object astronomers have detected in our planetary neighborhood, thanks to advanced new detection methods that are expected to reveal that such visits are a much more common occurrence than previously known.
As the interstellar voyager continues its journey, which will carry it past the planet Mars next month, 3I/ATLAS will then make its closest approach to Earth, at which time it will be obscured from view as it travels behind the Sun.
Although its trajectory will prevent us from getting a very clear close-up view of the comet, the years ahead are almost guaranteed to grant astronomers additional opportunities to observe interstellar objects like 3I/ATLAS, presenting us with exciting new opportunities to learn about them.
We Are Not Alone: More Objects like 3I/ATLAS are on the Way
“We expect to discover many more interstellar objects in the coming decades, as the Vera C. Rubin Observatory’s Legacy Survey of Space and Time is underway,” said Aster Taylor, a Ph.D. student and a Fannie and John Hertz Foundation Fellow at the University of Michigan, in an email to The Debrief.
Taylor says that with the potential for several new interstellar object discoveries over the period of the Rubin Observatory’s decade-long survey, astronomers may soon have ample opportunities to learn about these mysterious visitors from distant regions of space.
So what makes the Rubin Observatory so special in the search for these objects, and why is it almost guaranteed to reveal that comets like 3I/ATLAS are less like rare celestial lone wolves, and more like periodic visitors we can expect to see more often?
The Rubin Observatory: Transforming the Hunt for Interstellar Objects
With just hours of observations under its astronomical belt as it entered its commissioning phase earlier this year, the Rubin Observatory in Chile had already successfully discovered more than 2,100 new asteroids. This offers an early glimpse at the observatory’s promising potential in the search for objects in our solar system, as well as any rare interstellar visitors that are likely to make their way here in the future.
Above: The Vera C. Rubin Observatory, as seen at night. Over the next decade, the observatory is expected to make several additional discoveries of interstellar objects (Credit: Vera Rubin Observatory/NSF/AURA/B. Quint).
In fact, during that same commissioning period, the Rubin Observatory already succeeded in detecting one confirmed interstellar object when it photographed 3I/ATLAS several days before its official discovery. However, the object wasn’t spotted in the imagery until later on, well after the discovery of the object had been confirmed by NASA.
Interstellar Objects and Beyond
Designed for a range of scientific objectives that include mapping the Milky Way and probing the evolution of the cosmos, fast-moving celestial objects like 3I/ATLAS and any future interstellar objects that come speeding through our solar system will also be harder to miss than in the past, when such high-speed bodies could easily slip by unnoticed.
Central to Rubin’s investigations in the coming years will be the observatory’s Large Synoptic Survey Telescope (LSST) camera, which represents the largest digital camera ever constructed for astronomy.
Armed with an astonishing 3.2 gigapixels, the LSST will be scanning massive portions of the night sky every week, regularly capturing imagery of the southern sky from its South American vantage point. Even some of the faintest and fastest-moving objects that happen to appear in distant reaches of the solar system will almost certainly be spotted with the help of Rubin’s automated alert system, which can process millions of individual signals on a nightly basis.
How Many Interstellar Visitors Might Turn Up?
Although Rubin will likely succeed in detecting interstellar objects like 3I/ATLAS in the future, the frequency of such detections remains uncertain, even though the advanced observatories now entering operation are better equipped to find them.
One reason for this involves the relatively small amount of data we currently have about these objects and their behavior, since 3I/ATLAS’s current transit marks only the third time astronomers have been able to observe such an object. This leaves many questions about their abundance, common shapes and sizes, how much light they reflect, and what kinds of materials they might be carrying with them across such vast interstellar distances.
Some studies in recent years have suggested that the Rubin observatory might discover as many as one to two interstellar objects per year, while others suggest objects of modest size—between around 3 and 164 feet—may be spotted only every couple of years.
“I believe that the current expectation is for order 1 detection a year,” Taylor told The Debrief in an email. “While that might not seem like much, we’ve already learned a lot from the 3 objects currently known.”
“Having ~15 would be a massive improvement in the sample size and vastly improve our understanding of interstellar objects’ composition, ages, and dynamics,” Taylor added. “I think that with that sample we’ll be able to calculate the production rate of interstellar objects over the history of the Galaxy and get a unique look into how planet formation has operated in the Galaxy over its lifetime.”
However, other studies are even more optimistic about the rate of such discoveries, suggesting that Rubin could successfully find as many as 70 asteroid-like interstellar objects each year, which would amount to nearly 700 detections over the next decade.
A New Era for Interstellar Objects
Despite the widespread estimates, what is clear is that Rubin’s capabilities vastly outstrip past surveys, and this alone has many astronomers excited. With its unprecedented ability to spot faint and speedy interstellar bodies that almost certainly would have evaded detection in the past, Rubin may very well be poised to bring encounters with interstellar objects like 3I/ATLAS out of the realm of astronomical curiosities and into routine science.
So even as remarkable as 3I/ATLAS is turning out to be, the hunt for interstellar visitors is only getting started. With little doubt, more cosmic messengers from beyond our solar system will soon be on their way… and in fact, they may soon be making frequent appearances in humanity’s most advanced telescopes.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.