For decades, astronomers have dismissed them as nuisances — small specks of rock streaking through telescope images, obscuring views of far-off stars. These asteroids, sometimes dubbed the “vermin of the sky,” have been little more than cosmic static for researchers focused on the universe beyond our solar system.

But now, scientists at MIT are seeing these space pebbles in a whole new light. Using data originally gathered for distant exoplanets and an image-processing technique borrowed from the 1990s, they’ve uncovered some of the tiniest asteroids ever detected in the main asteroid belt — space rocks just 10 meters across, about the size of a bus. These discoveries could play a critical role in our understanding of planetary defense and the origins of meteorites that sometimes strike Earth.

Specks on a Belt

The asteroid belt is a sprawling field of debris between Mars and Jupiter, home to millions of rocky fragments left over from the formation of the solar system. Until now, scientists could only identify main-belt asteroids that were at least a kilometer wide. Anything smaller was too faint to spot against the noise of telescope images.

Enter Julien de Wit and Artem Burdanov of MIT, who realized there was a treasure trove hidden in that noise.

“For most astronomers, asteroids are sort of seen as the vermin of the sky,” de Wit says. “In the sense that they just cross your field of view and affect your data.”

But de Wit and his colleagues saw potential. They wondered if the same images used to hunt for distant exoplanets could also reveal asteroids closer to home. To test their idea, they applied a technique called “shift and stack” to images captured by the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) and the SPECULOOS survey, both designed to search for exoplanets.

The method is deceptively simple. By shifting multiple images of the same patch of sky and stacking them together, faint objects that would otherwise be lost in the noise can be teased into view. With modern computing power, the team could process thousands of potential scenarios for where an asteroid might be hiding, revealing a multitude of previously unseen space rocks.

What This Means For Planetary Defense

Their breakthrough came when they applied this approach to data from NASA’s James Webb Space Telescope (JWST). The JWST, primarily designed to explore distant galaxies and exoplanets, excels at detecting infrared light — and its instruments are so sensitive it can detect even the warmth of small, distant asteroids.

In images originally intended to study the TRAPPIST-1 star system, the MIT team found something unexpected: eight known main-belt asteroids and 138 previously unknown ones. These newfound asteroids ranged from the size of a bus to several stadiums wide, marking the smallest main-belt asteroids ever detected.

“We thought we would just detect a few new objects, but we detected so many more than expected, especially small ones,” de Wit says. “It is a sign that we are probing a new population regime.”

These tiny asteroids matter more than their size suggests. While colossal impactors like the one that ended the age of dinosaurs are rare — striking Earth perhaps once every 100 million to 500 million years — smaller asteroids are far more common. A rock the size of a bus can still pack a punch, as seen in 2013 when an asteroid exploded over Chelyabinsk, Russia, shattering windows and injuring over 1,500 people.

With the ability to spot these decameter-sized asteroids while they’re still in the asteroid belt, scientists can improve their ability to track potentially dangerous objects long before they approach Earth.

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

New Technology, New Horizons

Beyond planetary defense, this discovery opens new possibilities for understanding the solar system’s evolution. The abundance of small asteroids supports the idea that these fragments are born from collisions that continually break larger asteroids into smaller pieces. The main asteroid belt, it turns out, is far more dynamic than once believed.

“This is a totally new, unexplored space we are entering, thanks to modern technologies,” Burdanov says. “It’s a good example of what we can do as a field when we look at the data differently.”

In the future, this technique could be applied to even more telescopic surveys, mining old data sets for hidden treasures. What was once discarded as interference now offers a new frontier for discovery. The vermin of the sky are getting their moment — and it turns out, they have a lot to teach.

The findings appeared in the journal Nature.