Astronomers discover smallest main belt asteroids

An international research team led by Massachusetts Institute of Technology (MIT) scientists announced the detection of 138 previously unknown asteroids in the main asteroid belt. The observations, utilizing data from the James Webb Space Telescope (JWST) of the National Aeronautics and Space Administration (NASA), pushed the detection threshold to 10 m (33 feet) in diameter. Previous detection capabilities were limited to objects around 1 km (0.62 miles) wide.

The discovery, achieved through advanced infrared imaging and powerful computing, has opened a new step forward in understanding asteroid populations and improving planetary defense.

“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,” Artem Burdanov, a research scientist at MIT’s Department of Earth, Atmospheric, and Planetary Sciences, stated.

The asteroid belt, a vast region between Mars and Jupiter’s orbits, is home to millions of asteroids of varying sizes. Finding smaller ones, the size of a bus or smaller, has been difficult compared to finding the larger asteroids, which are well-studied.

The detected asteroids range in size from 10 m to several 100 m (656 feet). Some may, with time, migrate closer to Earth by entering the category of near-Earth objects (NEOs).

One asteroid identified is suspected to be a Trojan, trailing Jupiter’s orbit. The findings also suggest a previously unexplored population of small objects formed through collision cascades in the asteroid belt.

“We thought we would just detect a few new objects, but we detected so many more than expected, especially small ones. It is a sign that we are probing a new population regime,” Julien de Wit, MIT professor of planetary science and study co-author, remarked.

Technological advances and methods

The discoveries were made possible through sophisticated imaging techniques known as “shift and stack.” The method involves aligning and combining multiple images of the same field to amplify faint moving objects, such as small asteroids.

The technique (originally developed in the 1990s) has gained new efficiency through modern graphics processing units (GPUs) capable of processing large datasets at high speeds.

The researchers processed over 10 000 images of the Transiting Planets and Planetesimals Small Telescope (TRAPPIST-1) system taken by the JWST. The data initially gathered to study exoplanetary atmospheres, was repurposed to detect faint signals from small asteroids. 8 known main-belt asteroids were identified and it was followed by the detection of 138 new objects.

Historical context and comparison

The main asteroid belt, first explored in the early 19th century, has seen substantial advancements in observational capabilities over the past 2 decades.

Most studies focused on kilometer-scale objects. The new detection limit, down to decameter-sized bodies, showed the exponential growth in our technological capabilities.

The team’s observations also build upon previous work utilizing the SPECULOOS survey and ground-based telescopes in Antarctica. The JWST’s infrared sensitivity provided a leap, as asteroids in the main belt emit more strongly in infrared than in visible light.

Use for planetary defense

Finding small asteroids from greater distances is important for planetary defense. Even though they are smaller than catastrophic impactors, asteroids about 10 m (33 feet) wide can cause serious regional damage, as seen in the 1908 Tunguska event in Siberia and the 2013 Chelyabinsk meteor.

The ability to track these smaller asteroids with precision is important for early warning systems.

“Our ability to spot these small asteroids when they are much farther away from Earth allows us to perform more precise orbital determinations, which are crucial for planetary defense,” Marco Micheli from the European Space Agency’s Near-Earth Object Coordination Centre, noted.

The role of infrared imaging

The JWST’s focus on infrared wavelengths has proven instrumental in detecting small asteroids. Infrared observations reduce uncertainties in size estimation compared to visible-light observations which often depend on the object’s albedo. This allows for more accurate measurements of an asteroid’s dimensions even when its orbit is not fully known.

“Our findings rely on a new and innovative technique to determine an asteroid’s size from simple infrared detections without knowing the object’s true orbit,” Thomas Müller of the Max-Planck-Institut in Germany explained.

Exploring asteroid families

Many of the newly discovered asteroids are thought to be fragments from collisions involving larger parent bodies. These fragments, grouped into “families” because they share similar orbits, help scientists understand the history of collisions in the asteroid belt.

The study identified associations with well-known families such as Nysa, Polana, and Massalia. The findings show the role of small asteroids in learning about how the solar system has evolved.

Future JWST observations focused on exoplanets could lead to more discoveries of small asteroids. Researchers plan to study over 15 exoplanet host stars near the ecliptic plane which may uncover hundreds of additional small asteroids in the coming years.

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

“It’s a good example of what we can do as a field when we look at the data differently.”

References:

1 JWST sighting of decameter main-belt asteroids and view on meteorite sources, Artem Y. Burdanov, Julien de Wit, Miroslav Broz, Thomas G. Muller, MIT – December 9, 2024 – https://dspace.mit.edu/handle/1721.1/157797 – OPEN ACCESS

2 MIT astronomers find the smallest asteroids ever detected in the main belt – MIT News – December 9, 2024

3 JWST – NASA – Accessed on December 12, 2024