Results
What should the LSST discover and when?
Using our Sorcha Solar System survey simulator , we have taken the best estimate for how Rubin Observatory will observe over the next ten years and combined with the best models of several of the Solar System's main populations look like. We have estimates for the number of objects detected, the total number of observations (and in what optical filters important for composition studies), and estimates for the brightnesses of these objects in each of the simulated survey observsations. Our picture of the Solar System will completely change with the start of the LSST. Our analysis shows that the Rubin Observatory will be an unrivaled Solar System small body discovery and follow-up machine.
Using the best estimates for what the key Solar System populations look like and how the LSST will observe, we have predictions for:
- Near-Earth objects (NEOs) are, as the name suggests, are small Solar System bodies that occasionally fly close to the Earth on their orbits. Some of them pose a threat to our planet. A continuous monitoring of their orbits and studying their composition with LSST is essential for the mitigation of the potential impact hazards.
- Main-belt asteroids (MBAs) , situated between Mars and Jupiter, comprise the bulk of small Solar System objects. Their population not only hides the history of planetary interactions in the early days of the Solar System, but also unveils a widest variety of different surfaces shaped by collisions, gas outbursts and thermal forces.
- Jupiter Trojans are asteroids that have become trapped through interactions with Jupiter's gravity. They are located along Jupiter's orbit and are found orbiting ahead or behind the giant planet.
- Centaurs are on planet-crossing orbits between Jupiter and Neptune. 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.
- Trans-Neptunian objects (TNOs) are found at the outskirts of the Solar System, starting from the orbit of Neptune, and beyond. Their orbital architecture is an imprint of the processes that have shaped the Solar System throughout its history and the orbits of the giant planets.
The Predictions by Numbers
Figure Credits: Image of Near-Earth asteroid Ryugu (Credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, Aizu University, AIST ); Image of asteroid Itokawa (credit: JAXA); Artist rendition of Centaur Chiron (Credit Flyazure); Images of Trans-Neptunian objects Pluto and Arrokoth (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)
Where and When in the Solar System
Each flashing white dot in the visualization below is a predicted Solar System small body is expected to be discovered by the LSST based on our simulations. The color the points fade to shows what class of object (red NEOs, yellow MBAs, lavender Jupiter Trojans, and blue TNOs). The left plot is a bird's eye view of the Solar System looking downward at the plane of the Solar System. The view on the right is looking at the Solar System edge on.
This simulation assumed that the LSST would start in April of 2025. The current expected start date is mid-to-late Autumn of this year.
The Scale of the New Discoveries
Here we plot the total number of objects that we predict the Rubin Observatory to find during the LSST. The light purple are the expected new discoveries from Rubin Observatory. The dark purple are the small bodies known to date. The sheer number of main-belt asteroids observed is whopping compared to any of the other populations in the Solar System we looked at.
Let's zoom in to see the TNOs, MBAs, and NEOs
Let's zoom in to focus on the Centaurs
Over 10 years, Rubin is expected to quintuple the number of known Centaurs: from around 300 today to around 1,500. And around half of those will be discovered in just the first year of Rubin’s operations. With over 300 Centaurs expected
to have high-quality surface color measurements (thanks to the LSST's observations in multiple broad-band filters), we’re looking at a tenfold increase in just 10 years compared to the past 30 of scientific literature.
Discoveries Over Time Across the Sky
The figure below shows the locations of Solar System discoveries across the night sky. In the first two years we expect 70% of the surveys's small body discoveries! For Centaurs, it will take a bit longer (about 4 years), but 50% of Centaur discoveries will discovered after one full year of LSST data.
The bulk of the Solar System objects will be found around the ecliptic plane (the grey solid wave-likeline), the plane of the Earth's orbit about the Sun. The orbits of most of the Solar System's small bodies and planets tend to be aligned close to the ecliptic.
The Solar System in Technicolor
Beyond just discovering these objects, most of the small bodies found by Rubin Observatory during the LSST will be imaged multiple times and in multiple filters. Most previous surveys typically only have a few observations of each object in a single broad-band filter, and information about each object's color, which indicates its composition, comes from expensive follow-up campaigns using other telescopes for a limited number of targets. Rubin does this differently, taking multiple images of each object in each of the six broad-band filters, so that a large fraction of objects measured by Rubin will have high-quality color measurements, thus measuring more colors than all of Rubin's predecessors combined. This means that future studies of the Solar System will be able to combine the orbital history of each object with what each object is made of, leading to an unprecedentedly detailed view of the Solar System.
