When the interstellar object (ISO) Oumuamua appeared in our Solar System in 2017, it generated a lot of interest. The need to learn more about this was fierce, but unfortunately, there was no way to do it. It came and went, and we were left to reflect on what it was made of and where it came from. Then in 2019, Comet ISO Borisov made a brief visit and we were again left wondering about it.
There will surely be more ISOs of this type crossing our Solar System. There has been talk of having missions ready to visit one of these interstellar visitors in the future, but for that to happen, we need advance notice of their arrival. Could the Vera Rubin Observatory inform us well in advance?
No mission leaves the launch pad without detailed planning, and detailed planning depends on observations. Terrestrial observations laid the foundation for our forays into the Solar System. NASA missions like OSIRIS-REx, Lucy and Psyche are simply impossible without detailed Earth observations to pave the way.
Soon, one of our most powerful and unique observatories will begin operating, the Vera Rubin Observatory. Its main activity will be Legacy study of space and time (LSST.) The LSST will image our Solar System in much more detail than ever before, and will do so continuously for a decade. The wealth of data emerging from those observations will be a huge benefit to mission planning and will likely inspire missions we haven’t yet dreamed of.
VRO’s Legacy Survey of Space and Time relies on the observatory’s 8.4-meter wide-angle primary mirror and its ability to change targets in just five seconds. Attached to it is the world’s largest digital camera, a 3.2 gigapixel behemoth. The VRO will image the entire available night sky every few nights.
The LSST aims to detect transients such as supernovae and gamma-ray bursts. It will also study dark energy and matter and map the Milky Way. But it will also map small objects in our Solar System, such as near-Earth asteroids (NEA) and Kuiper Belt objects (KBO).
“Nothing will come close to the depth of Rubin’s study and the level of characterization we will get of Solar System objects,” said Siegfried Eggl, an assistant professor at the University of Illinois at Urbana-Champaign and leader of the Solar System Working Group. Interior within the Rubin/LSST Solar System Science Collaboration. “It’s fascinating that we have the ability to visit interesting objects and observe them up close. But to do that we need to know that they exist and we need to know where they are. This is what Rubin will tell us.”
It is difficult to overstate how the VRO and its LSST will improve our understanding of the Solar System. There are other survey telescopes, such as Pan-STARRS (Panoramic reconnaissance telescope and rapid response system). Pan-STARRS has detected a large number of astronomical transients. Its job is to detect them and alert astronomers so that other telescopes can observe them.
Pan-STARRS is based on two telescopes with 1.8-meter mirrors and is our most effective near-Earth object (NEO) detector, but once the VRO is operational, it will be relegated to a distant second place.
Interestingly, the VRO will also detect ISO. In a 2023 article, researchers estimated that the VRO will detect up to 70 interstellar objects each year. If the VRO can see them early enough, it could give us time to launch a mission to one of them.
“Rubin is capable of giving us the preparation time we need to launch a mission to intercept an interstellar object,” Eggl said. “That’s a synergy that’s very unique to Rubin and unique to the times we live in.”
It is not clear how many ISOs visit our Solar System each year and will be detectable. While some researchers suggest the VRO can detect 70 per year, others say the number will be smaller. VRO is not magic. Objects that are too dark and/or moving too fast may escape detection. But it seems certain that the LSST will detect some ISOs. You can even discern patterns in their trajectories that make it easier to detect more of them.
As our knowledge of ISOs grows, the need to visit one will grow with it. The emergence of Oumuamua and Borisov shows that opportunities will continue to present themselves. There are already preliminary plans on how to visit one.
ESA’s Comet Interceptor is designed to visit a long-period comet. The Interceptor mission has three spacecraft, and each one will study the comet from a different angle, providing a 3D view. Advance warning is critical to the Comet Interceptor mission, and ESA specifically mentions that LSST enables the mission by alerting us to an appropriate target early enough.
But the target does not have to be a comet. It could be anything that travels through the inner Solar System.
The only thing about Comet Interceptor is that it will already be stalking its target. After launch, it will travel to the Sun-Earth Lagrange 2 point (L2). It will enter a halo orbit there and await further instructions. ESA can bide their time until the VRO detects a desirable target on the correct trajectory and they can activate the Comet Interceptor.
NASA’s Lucy mission shows how advanced knowledge of Solar System objects enables powerful missions. Lucy is based on exact observations of Solar System objects and will visit several asteroids touring the inner Solar System, using Earth as a gravitational assist on three separate occasions. Detailed knowledge of the Solar System inspired and enabled Lucy’s mission.
The Comet Interceptor, or another similar mission, will not need such a complex path. But like Lucy, it will depend on keen observations, something the VRO and LSST will provide in great depth.
The LSST will not only enable missions like the Comet Interceptor. It will inspire new ones that we cannot yet imagine. This is because we don’t yet know what the survey will reveal. It could uncover regions of objects that behave in ways we haven’t seen yet or types of grouped objects that have remained invisible.
“If you think of Rubin as looking at a beach, you’ll see millions and millions of individual sand grains that together make up the entire beach,” Eggl said, “There may be an area of yellow sand or black volcanic sand, and a space. to an object in that region could investigate what makes it different. Often, we don’t know what is strange or interesting unless we know the context it is in. With our current telescopes, we have basically been looking at the big rocks on the beach “says Eggl, “but Rubin will approach the finer grains of sand.”
The Jupiter Trojan asteroids that Lucy will visit are a good example of this. This type of asteroid was predicted to exist back in the 1770s, but the first one wasn’t seen until more than a century had passed. Even then, no one was sure that it was actually a Trojan asteroid until almost another century had passed. Now astronomers know there are thousands of them.
Similarly, our knowledge of ISOs could become much more complete once the LSST gets underway. A completely new window could open towards ISOs. Astronomers can discern patterns in their trajectories and composition that lead to new insights into their origins. If Comet Interceptor or a similar mission is sent to one of them, we will learn more about how planetary systems, including our own, form.
Not everything in our Solar System formed where we see it today. Some bodies have been captured, such as Neptune’s moon Triton, which is likely a captured Kuiper Belt object. Astronomers believe that it is very likely that some of the objects in our Solar System are ISO captured. The VRO and the missions it inspires could identify these objects.
New observations lead to new questions and new missions designed to answer them. That is a long-standing pattern in our quest to understand nature.
Who knows what the VRO will see and what future missions will lead its findings?