Astronomers find the smallest asteroids ever detected in the main belt

By comparison, much smaller asteroids (about the size of a bus) hit Earth more frequently every few years. These “decameter” asteroids are only a few tens of meters in diameter and are more likely to escape the main asteroid belt and migrate to become near-Earth objects. These small but powerful space rocks can send shock waves across an entire region in the event of an impact, such as the 1908 Tunguska impact in Siberia and the 2013 shattering asteroid over Chelyabinsk in the Urals. Being able to observe ten-meter-long main-belt asteroids will provide a window into the origins of meteorites.

Now, MIT astronomers have found a way to discover the smallest ten-meter asteroids in the main asteroid belt — the debris field between Mars and Jupiter where millions of asteroids orbit . So far, the smallest asteroid scientists have been able to identify is about one kilometer in diameter. With the team’s new method, scientists can now find asteroids as small as 10 meters in diameter in the main belt.

In a paper published in the journal natureDeWitt and colleagues report that they have detected more than 100 new ten-meter asteroids in the main asteroid belt using their method. These space rocks range in size from the size of a bus to the width of several stadiums and are the smallest asteroids ever discovered within the Main Belt.

The researchers envision that this method could be used to identify and track asteroids that may approach Earth.

“We have been able to detect NEOs as small as 10 meters in size when they come very close to Earth,” said the study’s lead author Artem Burdanov, a research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “Now there’s a way to spot these small asteroids at greater distances, allowing us to do more precise orbital tracking, which is crucial for planetary defense.”

Study co-authors include MIT planetary science professors Julien de Wit and Richard Binzel, as well as collaborators from multiple other institutions.

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DeWitt and his team focus on searching for and studying exoplanets—potentially habitable worlds outside our solar system. The researchers were part of the team that discovered in 2016 the planetary system surrounding TRAPPIST-1, a star about 40 light-years from Earth. The research team used Chile’s Transiting Planets and Planets Small Telescope (TRAPPIST) to confirm that the star hosts Earth-sized rocky planets, several of which are in the habitable zone.

Since then, scientists have trained a number of telescopes focused on different wavelengths on the TRAPPIST-1 system to further characterize planets and search for signs of life. Through these searches, astronomers must filter out “noise” in the telescope’s images, such as any gas, dust and planetary objects between Earth and the star, to more clearly decipher the TRAPPIST-1 planets. Often, the noise they discard consists of passing asteroids.

“To most astronomers, asteroids are sort of seen as pests in the sky because they just cross your field of view and affect your data,” DeWitt said.

DeWitt and Burdanov wondered whether the same data used to search for exoplanets could be recycled and mined for asteroids in our own solar system. To do this, they looked to “shifting and stacking,” an image processing technique first developed in the 1990s. This method involves moving multiple images of the same field of view and stacking the images to see if otherwise faint objects can be obscured by the noise.

Applying this method to search for unknown asteroids in images originally focused on distant stars will require significant computational resources, as it will involve testing a large number of scenarios where asteroids may be located. The researchers then had to move through thousands of images for each scenario to see if the asteroid was actually where it predicted it would be.

A few years ago, Burdanov, de Wit and MIT graduate student Samantha Hassler discovered they could do this using state-of-the-art GPUs, graphics processing units that can process large amounts of imaging data at high speeds.

They initially tried the method using data from the SPECULOOS (Search for Habitable Planets Beyond Ultracool Stars) survey, a system of ground-based telescopes that takes many images of stars over time. This work, and a second application using telescope data in Antarctica, shows that researchers can indeed discover a large number of new asteroids in the main belt.

“Unexplored space”

In the new study, researchers used data from the world’s most powerful observatory, NASA’s James Webb Space Telescope (JWST), to search for more and smaller-sized asteroids. Visible light is particularly sensitive. In fact, asteroids orbiting in the main asteroid belt are much brighter at infrared wavelengths than at visible wavelengths, making them easier to detect using JWST’s infrared capabilities.

The team applied their method to JWST images of TRAPPIST-1. The data includes more than 10,000 images of stars originally acquired to look for signs of atmospheres around planets in the system. After processing the images, the researchers discovered eight known asteroids in the main belt. Then they further observed and discovered 138 new asteroids around the main belt, all with diameters within tens of meters. This is the smallest main belt asteroid detected so far. They suspect that several asteroids are becoming near-Earth objects, one of which is likely a Trojan – a Jupiter-tracking asteroid.

“We thought we would only detect a few new objects, but we detected many more objects than expected, especially small objects,” DeWitt said. “This is a sign that we are exploring a new population system. , forming more small bodies through cascading collisions, and these collisions can very effectively break up asteroids below about 100 meters.”

“Thanks to modern technology, we are entering a completely new and unexplored space,” Burdanov said. “This is a great example of what we can do as a field when we look at data differently. Sometimes there are big rewards, and this is one of those times.”

This work was supported in part by the Heising-Simons Foundation, the Czech Science Foundation, and the NVIDIA Academic Hardware Grant Program.