Simulation software highlights Rubin's potential
Published 6 June 2025
An international team of astronomers has created an innovative open-source software named Sorcha that will predict which discoveries are likely to be made by the NSF–DOE Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST).
Led by Dr Megan Schwamb of Queen’s University Belfast, the team includes researchers from Queen’s University Belfast, the University of Washington, the Center for Astrophysics | Harvard & Smithsonian, and the University of Illinois Urbana-Champaign.
According to team member Joe Murtagh: "The software acts as a 'predictive lens' for the LSST, highlighting which solar system objects the survey will detect – when, where, and how often – so that astronomers can account for observational biases from the start.
"This sort of forecast helps us refine our models of planetary formation, prioritise high-impact follow-up observations, and extract the full scientific value from the LSST’s groundbreaking dataset to create a true census of the solar system."
What has Sorcha predicted?
The simulation software has forecast 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.
As the Rubin Observatory prepares to reveal its First Look images on 23 June, the team's work reveals how Rubin will help us to understand the cosmos in new ways. "With the LSST, astronomers will have access to multi-filter measurements for over ten million main belt asteroids, tens of thousand of trans-Neptunian objects, and hundreds of Centaurs – all being observed repeatedly over the next 10 years," says Murtagh.
"In the first year alone, thousands of these objects will be seen in all six of the LSST’s filters, and it won’t stop there! As the LSST begins to deliver a true 'technicolour' view of the solar system over the next ten years, we’ll be able to combine detailed orbital histories with rich surface colour information to probe the present and past of the solar system in an unprecedented scale."
A series of papers by the team describing the software and the predictions are soon to be published by The Astronomical Journal.
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Image credit: RubinObs/NSF/DOE/NOIRLab/SLAC/AURA/H. Stockebrand