Mystery Objects From Other Stars Are Visiting Our Solar System. These Missions Will Study Them Up Close

In late 2017, a mysterious object tore through our solar system at breakneck speed. Astronomers scrambled to observe the fast moving body using the world’s most powerful telescopes. It was found to be one quarter mile (400 meters) long and very elongated—perhaps 10 times as long as it was wide. Researchers named it ‘Oumuamua, Hawaiian for “scout.”

'Oumuamua was later confirmed to be the first object from another star known to have visited our solar system. While these interstellar objects (ISOs) originate around a star, they end up as cosmic nomads, wandering through space. They are essentially planetary shrapnel, having been blasted out of their parent star systems by catastrophic events, such as giant collisions between planetary objects.

Astronomers say that 'Oumuamua could have been traveling through the Milky Way for hundreds of millions of years before its encounter with our solar system. Just two years after this unexpected visit, a second ISO—the Borisov Comet—was spotted, this time by an amateur astronomer in Crimea. These celestial interlopers have given us tantalizing glimpses of material from far beyond our solar system.

But what if we could do more than just watch them fly by?

Studying ISOs up close would offer scientists the rare opportunity to learn more about far off star systems, which are too distant to send missions to.

There may be over 10 septillion (or ten with 24 zeros) ISOs in the Milky Way alone. But if there are so many of them, why have we only seen two? Put simply, we cannot accurately predict when they will arrive. Large ISOs like 'Oumuamua, that are more easily detected, do not seem to visit the solar system that often, and they travel incredibly fast.

Ground- and space-based telescopes struggle to respond quickly to incoming ISOs, meaning that we are mostly looking at them after they pass through our cosmic neighborhood. However, innovative space missions could get us closer to objects like 'Oumuamua, by using breakthroughs in artificial intelligence (AI) to guide spacecraft safely to future visitors. Getting closer means we can get a better understanding of their composition, geology, and activity—gaining insights into the conditions around other stars.

Emerging technologies being used to approach space debris could help to approach other unpredictable objects, transforming these fleeting encounters into profound scientific opportunities. So how do we get close? Speeding past Earth at an average of 32 kilometers per second, ISOs give us less than a year for our spacecraft to try and intercept them after detection. Catching up is not impossible—for example, it could be done via gravitational slingshot maneuvers. However, it is difficult, costly and would take years to execute.

The good news is that the first wave of ISO-hunting missions is already in motion: NASA’s mission concept is called Bridge and the European Space Agency (ESA) has a mission called Comet Interceptor. Once an incoming ISO is identified, Bridge would depart Earth to intercept it. However, launching from Earth currently requires a 30-day launch window after detection, which would cost valuable time.

The Comet Interceptor mission is scheduled to launch in 2029. ESA / Work performed by ATG under contract to ESA, CC BY-SA

Comet Interceptor is scheduled for launch in 2029 and comprises a larger spacecraft and two smaller robotic probes. Once launched, it will lie in wait a million miles from Earth, poised to ambush a long period comet (slower comets that come from further away)—or potentially an ISO. Placing spacecraft in a “storage orbit” allows for rapid deployment when a suitable ISO is detected.

Another proposal from the Institute for Interstellar Studies, Project Lyra, assessed the feasibility of chasing down 'Oumuamua, which has already sped far beyond Neptune’s orbit. They found that it would be possible in theory to catch up with the object, but this would also be very technically challenging.

The Fast and the Curious

These missions are a start, but as described, their biggest limitation is speed. To chase down ISOs like 'Oumuamua, we’ll need to move a lot faster—and think smarter.

Future missions may rely on cutting-edge AI and related fields such as deep learning—which seeks to emulate the decision-making power of the human brain—to identify and respond to incoming objects in real time. Researchers are already testing small spacecraft that operate in coordinated “swarms,” allowing them to image targets from multiple angles and adapt mid-flight.

At the Vera C Rubin Observatory in Chile, a 10-year survey of the night sky is due to begin soon. This astronomical survey is expected to find dozens of ISOs each year. Simulations suggest we may be on the cusp of a detection boom.

Any spacecraft would need to reach high speeds once an object is spotted and ensure that its energy source doesn’t degrade, potentially after years waiting in “storage orbit.” A number of missions have already utilized a form of propulsion called a solar sail.