Asteroids found in the main belt are the smallest ever detected

The solar system’s main asteroid belt, located between Mars and Jupiter, is home to millions of rocky objects.

These asteroids orbit at an average of 250 million kilometers (155 million miles) from Earth. They range in size from large celestial bodies like Vesta, which measures about 530 kilometers (329 miles) in diameter, to countless smaller fragments.

Despite their abundance, the total mass of these asteroids is less than that of Earth’s Moon.

Over the last decade, extensive optical surveys have cataloged nearly 750,000 asteroids that are larger than one kilometer in diameter, but the smallest ones have largely remained elusive – until now.

Asteroids and their impact on Earth

Asteroids occasionally find their way into Earth’s neighborhood, nudged by the gravitational influence of Mars and Jupiter.

Known as Near-Earth asteroids (NEAs), these objects have historically impacted Earth and other planets, shaping their geological and evolutionary paths.

Their potential threats to Earth have made their detection and tracking critical for planetary defense efforts.

Small main-belt asteroids

A recent study led by MIT astronomers Julien de Wit and Artem Burdanov has leveraged data from NASA’s James Webb Space Telescope (JWST) to spot the smallest main-belt asteroids ever detected.

This effort, which involved researchers from the University of Liège (ULiège) and other institutions, highlights how advanced technologies and innovative techniques can reveal hidden aspects of the solar system.

“The study of small bodies of the solar system is of high importance as they give us a unique view of the early phases of our system, even before the planets formed,” explained Emmanuel Jehin, a planetary scientist at ULiège.

“Being able to observe the smallest main-belt asteroids would not only give us clues about the building blocks of planets but also provide a unique window into the source of meteorites falling on Earth.”

Exoplanet data for main-belt asteroids

Although De Wit and Burdanov initially focused on exoplanet studies, they subsequently adapted their expertise to search for asteroids.

Their team, renowned for discovering the TRAPPIST-1 planetary system, utilized JWST’s sensitivity to infrared light to identify asteroids. Infrared wavelengths are particularly advantageous for observing main-belt asteroids, as these objects appear brighter in infrared than in visible light.

The researchers applied a technique called “shift and stack,” which was originally developed in the 1990s. This method involves aligning and stacking multiple images of the same field to highlight faint, moving objects.

Using state-of-the-art GPUs, the team processed over 10,000 JWST images of the TRAPPIST-1 field that were originally intended for exoplanetary studies.

Discoveries in the main asteroid belt

This innovative approach revealed eight known asteroids and 138 previously undetected ones that ranged in diameter from 10 to several tens of meters. These tiny asteroids represent a new population of main-belt objects.

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

The findings suggest that many of these small asteroids are fragments from larger collisions, offering critical insights into asteroid population dynamics.

“Statistics of these very small, main-belt asteroids are critical for modeling the asteroid population,” explained Miroslav Broz from Prague’s Charles University. These smaller fragments, often linked by shared orbits, form asteroid families that provide clues to their origins.

Implications for planetary defense

The study’s results on main-belt asteroids have far-reaching implications for planetary defense. By detecting small asteroids further from Earth, scientists can track their orbits better and assess potential threats.

Marco Micheli from the European Space Agency’s Near-Earth Object Coordination Centre emphasized the importance of precise orbital determinations enabled by JWST’s capabilities.

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

Broader context of asteroid science

Asteroids vary widely in size and impact potential. While massive impactors.like the one that potentially caused the extinction of the dinosaurs are rare, smaller asteroids strike Earth more frequently – sometimes with significant consequences.

Observing and understanding these smaller objects is vital for both scientific discovery and practical applications, such as modeling potential impact events.

“It is fantastic to see how archived JWST data can open new doors to a better understanding of the smallest asteroids, which play a crucial role in planetary defense,” noted Thomas Müller from the Max Planck Institute.

A new era in asteroid research

This study of main-belt asteroids exemplifies how interdisciplinary collaboration and advanced technology can drive unexpected discoveries.

By repurposing exoplanetary data, researchers have uncovered a new layer of the solar system’s complexity, and paved the way for future breakthroughs in asteroid science and planetary defense.

As de Wit and his colleagues continue their work, their findings showcase the power of looking at existing data through a new lens. Whether studying distant exoplanets or nearby asteroids, the JWST continues to prove an invaluable tool for exploring the universe.

The study is published in the journal Nature.

Image Credit: Ella Maru

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