By the time its 7,000-pound digital camera was set in place, and its house-sized nest of mirrors had been perfectly aligned, astronomers felt that the Vera C. Rubin Observatory was going to be a spellbinding success. But this past spring, when it had captured its first view of the cosmos, they knew it. And in June, when scientists unveiled Rubin’s shimmering landscape of intertwining galaxies and opalescent nebulas to the world, everyone else knew it too.

Rubin, sitting atop an arid mountain range in Chile, is about to start a ten-year survey of the night sky. Thanks to its giant eyepiece, and its ability to drink up even the faintest starlight, it is the most perceptive cartographer of the cosmos ever built. It will chronicle distant exploding stars and ancient galaxies. It will scope out swarms of asteroids and even hidden planets in our own solar system.

Much has been written about Rubin’s omniscience. But there is another aspect to the observatory that, for now, is underappreciated: it will turn astronomers into archaeologists.

If our solar system was a map, the benighted fringes of it would be where sailors would mark “here be dragons”. And up until July 2025, in the pre-Rubin era, they had found two such serpents: a cigar-shaped oddity, and a comet-like vessel. These voyagers – named ‘Oumuamua and 2I/Borisov, respectively – are interstellar objects, visitors from other stars. They are geologic time capsules: pieces of a long-lost world or moon, or construction material that failed to coalesce into either.

“Each of these interstellar objects gives us the opportunity to poke into another solar system,” says Olivier Hainaut, an astronomer at the European Southern Observatory. But astronomers found ‘Oumuamua and Borisov serendipitously; they caught all-too-brief glimpses of them as they hastily slipped back into shadowed space. So much about them, including their provenances, remains unknown. Scientists simply didn’t have enough time to study them.

Its all-seeing eye will spy even the stealthiest of interstellar objects taking the plunge into our solar system—giving astronomers plenty of lead time to train their own sniper-like scopes on these interlopers. By examining them up close, and by tracing their orbits out over a protracted period of time, scientists will come to know what’s being excised from other star systems. They might even be able to identify the original stars themselves.

Thanks to Rubin’s reconnaissance, the ruins of alien worlds will be ours to peruse. “They’re coming,” says Meg Schwamb, a planetary scientist and astronomer at Queen’s University Belfast. “And we’re prepared.”

The overarching mission of the Rubin Observatory is to understand two puzzling and as-yet-undetected aspects of the universe. The first is dark matter, an invisible adhesive that seems to be binding visible matter together more tightly than gravity alone can explain. The second is dark energy, an undulating force that seems to be speeding up the expansion of reality. One way to decode both is to inventory everything in the night sky: if you know where everything is, and how it moves and transforms over time, you can put some constraints on the nature of dark matter and dark energy.

That’s exactly what Rubin’s going to do—almost effortlessly so. The solar system alone is suddenly going to become a very crowded place: in a few years, Rubin will discover a suite of new moons zipping around Jupiter, Saturn, Uranus and Neptune, 3.7 million new asteroids in the main belt between Mars and Jupiter, 89,000 asteroids with near-Earth orbits, 32,000 icy objects beyond Neptune, a hidden planet or two at the edges of the solar system—and a number of interstellar objects, too.

Asteroids and comets are the flotsam and jetsam that didn’t quite make it into making a planet or moon—or, in some cases, they are the wreckage left behind by a cataclysmic world-destroying event. Interstellar objects are very much the same thing, but with different addresses.

“Each interstellar object that comes through will come from a different planetary system,” says Sarah Greenstreet, an astronomer at the University of Washington. “They are also clues for us about how our own solar system formed.”

One way to answer that question is to spot an interstellar object paying our own solar system a visit and then finding out what it’s made of. “A few years, we had zero,” says Hainaut. “Then we discovered one. And that one was completely different from everything we ever expected.”

The story of the first-known interstellar object – eventually named ‘Oumuamua – is long, fascinating and complex. Here are the pertinent facts. It was discovered by the Pan-STARRS telescope in Hawai‘i – a facility chiefly tasked with identifying near-Earth asteroids – in October 2017. By that point, ‘Oumuamua was already leaving the solar system. The object wasn’t round, but cylindrical. It sped up as it swung around our star, as any object would, but its acceleration was so fast that another source of propulsion must have been involved—one that nobody was able to detect.

A few disingenuous types reckoned that the best explanation was that ‘Oumuamua was an alien spacecraft. (Spoiler alert: it wasn’t.) Astronomers largely suspected it was a peculiar comet-like object, one whose vaporizing ices gave it a Sun-escaping speed boost. But they didn’t have sufficient time to examine it to provide any definitive answers. Whatever ‘Oumuamua was, and wherever it came from, there is one thing that everyone can agree on. “It was super weird,” says Hainaut.

In August 2019, amateur astronomer Gennady Borisov caught sight of the second-known interstellar object, one soon named 2I/Borisov. This time, NASA’s Hubble Space Telescope and the National Radio Astronomy Observatory’s Atacama Large Millimeter/submillimeter Array (or ALMA facility) managed to zero-in on it before it evaded astronomers’ collective grasp. They found that it was a more run-of-the-mill comet, albeit one with an abundance of carbon monoxide ices.

“Now, we have two classes of objects,” says Hainaut. “Fifty percent are weird; fifty percent are what we expect.”

Any scientist worth their salt will tell you that a sample size of two is too small. Many suspect Borisov-like objects are more common than ‘Oumuamuas. “Most of them should be cometary,” says Greenstreet. But who knows?

Reasoned speculation has long been the only option—until, of course, Rubin swaggered onto the scene. There is no doubt that it’ll be able to see interstellar objects when its survey gets going. But how often do these messengers pay our solar system a visit? “It’s hard to know for sure,” says Greenstreet. “We don’t know how efficient planetary systems are at ejecting comets and asteroids out of their systems.”

Estimates for how many interstellar objects Rubin will discover during its decade-long quest range from a very pessimistic zero to several dozen. Hainaut’s best guess? “Anything between very few and several,” he says, with a smirk. Let’s conservatively say that Rubin finds a handful of them. “That means we get to directly probe a few different solar systems.”

Rubin’s survey of the night sky is largely automated. When it sees an object moving about up there that astronomers have no record of, it will immediately flag it to the relevant group of scientists. So, if an interstellar object is spotted, solar system scientists will hear a klaxon go off. Within a matter of hours (or even minutes), “there’s going to be an armada of telescopes pointed at whatever’s coming our way,” says Schwamb.

Rubin’s a multitalented telescope. But it can’t zoom in on objects in the way, for example, the James Webb Space Telescope or the ground-based Very Large Telescope (also, like Rubin, atop a Chilean mountain) can. These telescopes also have special filters on them allowing them to see objects in the infrared, which can tease out more detail about their shapes, sizes and rock-ice compositions. This granular follow-up work can tell us how similar or different these objects are to the planetary shards flying around our own solar system, says Pedro Bernardinelli, an astronomer at the University of Washington.

Rubin will also be able to detect interstellar objects “while they’re still far away from the Sun,” says Mario Jurić, an astronomer at the University of Washington. Something like Borisov should be detectable by the observatory more than a year before its closest approach to our local star. That means astronomers can see it erupt, spin, and evolve as its ices get cooked by the Sun—offering more clues as to its composition and its internal structure.

Optimistically, astronomers hope to find the return addresses of these objects. If Rubin does spot them coming into the solar system very early on, then scientists will be able to map out their orbits with great precision—so much so that, just maybe, “we can pinpoint the star they came from,” says Hainaut. That’s the different between finding an ancient dagger in the middle of the ocean and finding one in the volcanic ruins of Pompeii itself.

For now, though, we must be patient: Rubin may have made its debut this summer, but its full survey has yet to begin. Even when it kicks off this fall, we don’t know how long it’ll take to find its first interstellar object—if it finds any at all.

Or perhaps not. On July 1st – just after Rubin’s debut images were shown to the world, but a few months before it was due to begin its full-spectrum survey – something curious was spotted erupting above our heads. The Asteroid Terrestrial-impact Last Alert System, a NASA-funded planetary defense facility designed to spot near-Earth objects, captured a small glimmer on its scopes. Then about 420 million miles from home, this object was crossing Jupiter’s orbit on a hyperbolic trajectory through our solar system. There was no mistaking it: scientists had serendipitously another interstellar voyager—their third-ever. And now they’re racing to study it as it sweeps around the Sun over the summer.

Hopes are high. It looks like astronomers are about to get a crash course in interstellar archaeology after all. What might the fourth, fifth…tenth voyagers be like? What stories of forgotten realms will they tell?

“We suspect that our neighbors are not too different. That’s a general rule of life,” says Hainaut. “But we might get surprises.”