Webb Detects 138 Decameter Asteroids in Main Belt | Sci.News

These asteroids are as small as 10 m across, making them the smallest asteroids ever observed in the main asteroid belt.

Asteroid discoveries are essential for planetary-defense efforts aiming to prevent impacts with Earth, including the more frequent megaton explosions from decameter impactors.

While large asteroids (=>100 km) have remained in the main belt since their formation, small asteroids are commonly transported to the near-Earth object (NEO) population.

“We have been able to detect NEOs down to 10 m in size when they are really close to Earth,” said Dr. Artem Burdanov, a researcher at MIT.

“We now have a way of spotting these small asteroids when they are much farther away, so we can do more precise orbital tracking, which is key for planetary defense.”

For the study, the astronomers looked for small asteroids using data from the NASA/ESA/CSA James Webb Space Telescope.

As it happens, asteroids that orbit in the main asteroid belt are much brighter at infrared wavelengths than at visible wavelengths, and thus are far easier to detect with Webb’s infrared capabilities.

The researchers were able to spot eight known asteroids in the main asteroid belt.

They then looked further and discovered 138 new asteroids around the belt, all within tens of meters in diameter — the smallest main-belt asteroids detected to date.

They suspect a few asteroids are on their way to becoming NEOs, while one is likely a Trojan — an asteroid that trails Jupiter.

“We thought we would just detect a few new objects, but we detected so many more than expected, especially small ones,” said MIT Professor Julien de Wit.

“It is a sign that we are probing a new population regime, where many more small objects are formed through cascades of collisions that are very efficient at breaking down asteroids below roughly 100 m.”

“This is a totally new, unexplored space we are entering, thanks to modern technologies,” Dr. Burdanov said.

“It’s a good example of what we can do as a field when we look at the data differently. Sometimes there’s a big payoff, and this is one of them.”

“Statistics of these very small main-belt asteroids are critical for modeling the asteroid population,” said Dr. Miroslav Broz, a researcher at the Prague Charles University.”

In fact, these are the debris ejected during collisions of bigger, kilometers-sized asteroids, which are observable and often exhibit similar orbits about the Sun, so that we ca group them into ‘families’ of asteroids.”

“We were not expecting that such impactful solar-system bonus science could be done using cutty-edge exoplanet observations,” said Dr. Michaël Gillon, a researcher at the University of Liège.

“Our ability to spot these small asteroids, thanks to Webb, when they are much farther away from Earth, allows us now to perform more precise orbital determinations, which are crucial for planetary defense,” said Dr. Marco Micheli, a researcher at ESA’s Near-Earth Object Coordination Centre.

The team’s paper was published today in the journal Nature.

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A.Y. Burdanov et al. JWST sighting of decameter main-belt asteroids and view on meteorite sources. Nature, published online December 9, 2024; doi: 10.1038/s41586-024-08480-z