Vera Rubin's keen eye on our solar system will inspire future missions


When the interstellar object (ISO) Oumuamua appeared in our solar system in 2017, it generated a lot of interest. There was a strong desire to learn more about it, but unfortunately, there was no way to actually do so. It came and went, and we had to consider what it was made of and where it came from. Then, in 2019, ISO Comet Borisov came by for a brief visit, and again, we were left in awe of it.

There are likely more such ISOs in our solar system. There has been talk of a mission being set up to meet one of these interstellar visitors in the future, but for that to happen, we need advance notice of its arrival. Could the Vera Rubin Observatory tell us far in advance?

No mission leaves the launch pad without detailed planning, and detailed planning depends on observation. Ground-based observations laid the foundation for our efforts in the Solar System. NASA missions like OSIRIS-REx, Lucy, and Psyche are impossible to chart without detailed ground observations.

Soon, one of our most powerful and unique observatories, the Vera Rubin Observatory, will begin operating. Its main activity will be the Legacy Survey of Space and Time (LSST). The LSST will image our solar system in more detail than ever before, and it will do so continuously for a decade. The wealth of data flowing from those observations will be a huge benefit to mission planning and will likely inspire missions we haven't even dreamed of yet.

VRO's legacy survey of space and time is based on the observatory's 8.4-metre, wide-angle primary mirror and the ability to change targets in just five seconds. Attached to it is the world's largest digital camera, a giant 3.2 gigapixel camera. VRO will image the entire available night sky every few nights.

The entire focal plane of the future LSST camera is more than 2 feet wide and contains 189 individual sensors that will produce 3,200-megapixel images.  (Jacqueline Orrell/SLAC National Accelerator Laboratory)
The entire focal plane of the future LSST camera is more than 2 feet wide and contains 189 individual sensors that will produce 3,200-megapixel images. (Jacqueline Orrell/SLAC National Accelerator Laboratory)

The LSST aims to detect transitions such as supernovae and gamma-ray bursts. It will also study dark energy and dark matter and map the galaxy. But it will also map smaller objects in our solar system, such as near-Earth asteroids (NEAs) and Kuiper Belt Objects (KBOs).

“Nothing will come close to the depth of Rubin's survey and the level of characterization we get for Solar System objects,” said Siegfried Eggl, an assistant professor at the University of Illinois Urbana-Champaign and head of the Inner Solar System Working Group. Rubin/LSST Solar System Science Collaboration. “It's fascinating that we have the ability to go to interesting objects and look at them up close. But to do that we need to know they exist, and we need to know where they are. That’s what Rubin will tell us.”

It is difficult to say how VRO and its LSST will advance our understanding of the Solar System. There are other survey telescopes, such as Pan-STARRS (Panoramic Survey Telescope and Rapid Response System.) Pan-STARRS has detected a large number of astronomical moments. Its job is to detect them and alert astronomers so other telescopes can observe them.

Pan-STARRS is based on two telescopes with 1.8-meter mirrors and is our most effective detector of Near-Earth Objects (NEOs), but once VRO is operational, it will take second place.

Interestingly, VRO will also detect ISOs. In a 2023 paper, researchers estimated that VRO would detect 70 interstellar objects each year. If VRO can see them early enough, that could give us time to launch a mission.

“Rubin is able to give us the preparation time needed to launch a mission to intercept an interstellar object,” Agle said. “It's a synergy that's very unique to Rubin and very unique to the times we live in.”

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This artist's image shows an interstellar object hurtling toward our solar system. The ISOs have somehow been ejected from their home systems, and some of them will travel through interstellar space forever. Others will visit systems like ours and offer themselves for study. Image credit: Rubin Observatory/NOIRLab/NSF/AURA/J. DaSilva/M. zamani

It is unclear how many ISOs visit our Solar System each year, and whether they will be detectable. While some researchers suggest VRO could detect 70 per year, others say the number will be lower. VRO is not magic. Objects that are too blurry and/or moving too quickly may escape detection. But it seems certain that LSST will detect some ISOs. It can also sense patterns in their trajectories making it easier to detect more of them.

As our knowledge of ISOs grows, so will our desire to see one of them. The presence of Oumuamua and Borisov shows that opportunities will continue to present themselves. There are already preliminary plans on how to visit someone.

ESA's Comet Interceptor is designed for long-duration comet visitation. The Interceptor mission has three spacecraft, and each will study the comet from a different angle, giving a 3D view. Advance notice is critical for comet interceptor missions, and ESA specifically cites LSST as enabling the mission by alerting us to appropriate targets early on.

But the target doesn't need to be a comet. It could be anything traveling through the inner solar system.

The unique thing about the Comet Interceptor is that it will already be sitting waiting for its target. After launch, it will travel to the Sun-Earth Lagrange 2 (L2) point. It will enter a halo orbit there and await further instructions. ESA can bide its 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 objects in the Solar System enables powerful missions. Lucy relies on precise observations of Solar System objects and will visit several asteroids by making their way through the inner Solar System, using Earth as a gravity assist, on three separate occasions. Detailed knowledge of the solar system made Lucy's mission inspiring and successful.

Comet Interceptor, or any other mission like it, would not require this complex path. But like Lucy, it will depend on deep observations, which VRO and LSST will provide at great depth.

The LSST will not only enable missions like Comet Interceptor. It will inspire new ones that we cannot yet imagine. This is because we do not yet know what the survey will reveal. It may uncover areas of objects that behave in ways we haven't yet seen or types of objects clumped together that have remained invisible.

“If you think of Rubin looking at a beach, you see millions and millions of individual sand particles that come together to form the entire beach,” Agle said, “There's yellow sand, or There may be an area and a place of volcanic black sand.” A mission to an object in that area can investigate what makes it different. Often, we don't know what's funny or interesting unless we know its context. With our current telescopes, we're essentially looking at large stones on the beach,” says Agle, “but Rubin will zoom in on fine 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 in the 1770s, but the first asteroid was not observed until more than a century had passed. Still, it wasn't until almost another century passed that anyone was sure it was actually a Trojan asteroid. Now, astronomers know they number in the thousands.

Similarly, our knowledge of ISO may become more complete once LSST is introduced. The ISO may open a whole new window. Astronomers can understand patterns in their trajectories and their structure, leading to new understanding of their origins. If Comet Interceptor or a similar mission is sent, we will learn more about how planetary systems form, including our own system.

Not everything in our solar system formed where we see it today. Some objects have been captured, such as Neptune's moon Triton, which is likely a captured Kuiper Belt object. Astronomers believe that it is highly likely that some objects in our solar system have been captured in ISO. VROs and missions inspired by them can identify these objects.

New observations give rise to new questions and new missions are designed to answer them. This is a long-term pattern in our quest to understand nature.

Who knows what VRO will see and what future missions its findings will lead to?


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