The JWST was never intended to find asteroids. It was built to probe some of our deepest, most demanding questions about the cosmos: how the first stars formed, how galaxies have evolved, how planets like ours take shape, and even how life originated. However, it\u2019s first and foremost a powerful infrared telescope and its unrivalled infrared prowess is helping it contribute to another important goal: defending Earth from dangerous asteroids.<\/p>\n
<\/p>\n Humanity doesn\u2019t want to share the dinosaurs\u2019 fate. About 66 million years ago, the Chicxulub impact wiped them out. An asteroid 10 to 15 km (6 to 9 mi) wide struck Earth near the Yucatan Peninsula, ending the dinosaurs\u2019 165-million-year reign. Only avian dinosaurs survived.<\/p>\n With that haunting backdrop, there\u2019s a growing effort to identify dangerous space rocks that could strike Earth. In 2005, the US Congress directed NASA to \u201cestablish a Near-Earth Object Survey Program to detect, track, catalogue, and characterize certain near-Earth asteroids and comets.\u201d That effort has paid dividends, especially when it comes to large asteroids that pose an existential threat.<\/p>\n Finding the largest main-belt asteroids hasn\u2019t been difficult. They practically announce their presence to our powerful telescopes. Large asteroids around 100 kilometres in diameter or greater are potentially devastating, but they tend to follow stable orbits in the main belt.<\/p>\n However, decameter-size impactors are more elusive. These are asteroids tens of meters in diameter, and their smaller masses mean they can more easily become part of the Near-Earth Object (NEO) population due to interactions in the main belt. While these aren\u2019t civilization-ending size rocks, they can reach Earth more frequently and cause megaton-size explosions. They\u2019re behind the Tunguska Event in 1908 and the Chelyabinsk explosion in 2013. <\/p>\n The JWST is helping scientists understand this population of space rocks, and new research illustrates how. It\u2019s titled \u201cJWST sighting of decametre main-belt asteroids and view on meteorite sources.\u201d It\u2019s published in Nature, and the co-lead authors are Julien de Wit and Artem Burdanov, both from the Department of Earth, Atmospheric, and Planetary Sciences at MIT.<\/p>\n \u201cAsteroid discoveries are essential for planetary-defence efforts aiming to prevent impacts with Earth, including the more frequent megaton explosions from decametre impactors,\u201d the authors write. \u201cAlthough large asteroids (~100 kilometres) have remained in the main belt since their formation, small asteroids are commonly transported to the near-Earth object (NEO) population.\u201d NEOs are objects whose closest approach to the Sun is less than 1.3 AU. This boundary includes objects that can come close enough to cross Earth\u2019s orbit or can be potentially influenced by Earth\u2019s gravity. <\/p>\n Most asteroids are detected with ground-based optical telescopes that sense the sunlight they reflect, which is their\u00a0albedo. Relying on asteroids\u2019 albedo measurements, though, is fraught with errors<\/span>. For example, small objects with a high albedo can appear larger than large objects with a small albedo. <\/p>\n Asteroids also give off thermal emissions or infrared energy, and that\u2019s where the JWST comes in. \u201cWith an exquisite sensitivity in that wavelength range and a large aperture, JWST is ideal for detecting the thermal emission of asteroids and revealing the smallest main-belt asteroids (MBAs),\u201d the authors write in their paper. <\/p>\n According to the researchers, the JWST\u2019s infrared measurements can constrain an object\u2019s size to within 10% to 20%, while albedo measurements alone can be off by a factor of 3-4x. That\u2019s a huge discrepancy that could lead to a risky misunderstanding of the main asteroid belt\u2019s population.<\/p>\n Burdanov, de Wit, and their co-researchers developed a new way to detect decametre-size impactors with the JWST by using GPUs, Graphics Processing Units, and what the researchers call \u201csynthetic tracking techniques.\u201d These were initially developed to hunt for exoplanets, but the method is bearing fruit in the effort to catalogue asteroids. The researchers\u2019 synthetic tracking method is designed to detect asteroids in data gathered from exoplanet observations. The JWST observed the TRAPPIST-1 star for more than 90 hours in 2022-23, and these results are based on that data.<\/p>\n \u201cAfter applying our GPU-based framework for detecting asteroids in targeted exoplanet surveys, we were able to detect 8 known and 139 unknown asteroids,\u201d the authors write. \u201cThe 139 new detections could not be attributed to any known asteroids.\u201d<\/p>\n They range from the size of a bus to several stadiums wide. They\u2019re the smallest objects ever detected in the main asteroid belt. <\/p>\n \u201cWe have been able to detect near-Earth objects down to 10 meters in size when they are really close to Earth,\u201d said author Artem Burdanov in a press release. \u201cWe 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 defence.\u201d<\/p>\n \u201cFor most astronomers, asteroids are sort of seen as the vermin of the sky, in the sense that they just cross your field of view and affect your data,\u201d study co-author Julien de Wit said.<\/p>\n![\"This](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2025\/02\/New-asteroids-main-belt.png\")