The NSF–DOE Vera C. Rubin Observatory is set to revolutionize our knowledge of the solar system’s “small bodies” - asteroids, comets, and other minor planets.

At the heart of the Rubin Observatory is the fastest moving telescope equipped with the world’s largest digital camera. A single image from the telescope covers a patch of sky roughly 45 times the area of the full moon.

Together, this “wide-fast-deep” system will spend the next ten years observing the night sky to produce the Legacy Survey of Space and Time (LSST). This will be an unprecedented time-lapse “movie” of the cosmos and a powerful dataset with which to map the solar system.

Innovative

The astronomers, led by Queen’s University’s Dr Meg Schwamb, have created innovative new open-source software to predict what discoveries are likely to be made. A series of papers describing the software and the predictions are soon to be published by The Astronomical Journal.

Dr Schwamb from the School of Mathematics and Physics at Queen’s says: “Our knowledge of what objects fill Earth’s solar system is about to expand exponentially and rapidly.”

Queen’s University Belfast PhD student Joe Murtagh is one of the lead authors of the prediction studies. His paper has also been submitted to The Astronomical Journal.

He says: “It’s very exciting – we expect that millions of new solar system objects will be detected and most of these will be picked up in the first few years of sky survey.”

Brilliant colour

Beyond just finding these new small bodies, Rubin Observatory will observe them multiple times in different optical filters, revealing their surface colours.  Past solar system surveys, typically observed only in a single filter.

Murtagh says: “With the LSST catalogue of solar system objects, our work shows that it will be like going from black-and-white television to brilliant colour.”

To forecast which small bodies will be discovered, the team built Sorcha, the first end-to-end simulator that ingests Rubin’s planned observing schedule. It applies assumptions on how Rubin Observatory observes and detects astronomical sources in its images with the best model of what the solar system and its small body reservoirs look like today. 

Dr Schwamb led the international team, which includes researchers from the University of Washington, the Center for Astrophysics | Harvard & Smithsonian, and the University of Illinois Urbana-Champaign. She explains: “Accurate simulation software like Sorcha is critical. It tells us what Rubin will discover and lets us know how to interpret it.”

The team’s simulations show that Rubin will map:

• 127,000 near-Earth objects - asteroids and comets whose orbits cross or approach Earth. That’s more than tripling today’s known objects, about 38,000, and detecting more than over 70% of potentially hazardous bodies larger than 140 metres. This will cut the risk of undetected asteroid impact of catastrophic proportions by at least two times, making a tremendous contribution to planetary defense.

• Over 5 million main-belt asteroids, up from about 1.4 million, with precise colour and rotation data on roughly one in three within the survey’s first years. This will give scientists unprecedented insight into the characteristics and history of the solar system’s building blocks.

• 109,000 Jupiter Trojans, bodies sharing Jupiter’s orbit at stable “Lagrange” points - more than seven times the number catalogued today. These bodies represent some of the most pristine material dating all the way back to the formation of the planets.

• 37,000 trans-Neptunian objects, residents of the distant Kuiper Belt — nearly ten times the current census — shedding light on Neptune’s past migration and the outer solar system’s history.

• Approximately 1,500-2,000 Centaurs, bodies on short-lived giant planet-crossing orbits in the middle solar system. Most Centaurs will eventually be ejected from the solar system, but a few lucky ones will survive to become short-period comets. The LSST will provide the first detailed view of the Centaurs and the important transition stage from Centaur to comet.  

Siegfried Eggl, Assistant Professor of Aerospace Engineering at the University of Illinois Urbana-Champaign, says: “Only by debiasing LSST’s complex observing pattern can we turn raw detections into a true reflection of the solar system’s history - where the planets formed, and how they migrated over billions of years. Sorcha is a game changer in that respect.”

Jake Kurlander, a PhD student at the University of Washington, who led one of the prediction studies, says: “This is what makes Rubin unique: it scans the sky comprehensively and quickly. It took 225 years to detect the first 1.5 million asteroids; we show that Rubin will double that in less than a year.”

Mario Juric is Professor of Astronomy at the University of Washington. He’s also Rubin’s Solar System Processing Pipelines team lead and a member of the Sorcha team at UW’s DiRAC Institute. He says: “Rubin Observatory’s LSST is our once-in-a-generation chance to fill in the missing pieces of our solar system.

“Our simulations predict that Rubin will expand known small-body populations by factors of 4–9x, delivering an unprecedented trove of orbits, colours and light curves. With this data, we’ll be able to rewrite the textbooks of solar system formation and vastly improve our ability to spot — and potentially deflect — the asteroids that could threaten Earth.”

The Sorcha code is open-source and freely available with the simulated catalogues, animations, and pre-prints of the papers publicly available at https://sorcha.space.

By making these resources available, the Sorcha team has enabled researchers worldwide to refine their tools and be ready for the flood of LSST data that Rubin will generate, advancing the understanding of the small bodies that illuminate the solar system like never before.

Rubin Observatory is scheduled to unveil its first spectacular imagery at its “First Look” event on June 23, offering the world an early glimpse of the survey’s power. Full science operations are slated to begin later this year.

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