In an international study led by Western University and Lowell Observatory, scientists have developed a pioneering approach for studying near-Earth asteroids. This approach was demonstrated through a November 2022 fireball event that dropped meteorites in the Niagara region. The research focuses on Asteroid 2022 WJ1 (WJ1), which fractured upon entering Earth's atmosphere.
By comparing Arizona-based telescopic observations with video captured by Western's Southern Ontario Meteor Network cameras of the fireball on November 19, 2022, the team determined WJ1's composition and size. The study, published in The Planetary Science Journal, reveals crucial details about WJ1, the smallest asteroid characterized to date, and establishes a new methodology for studying future impactful space objects.
This marks the first instance where telescope observations and ground camera captures have been combined to study the same astronomical body. The size of WJ1 was assessed using the 4.3-meter Lowell Discovery Telescope (LDT) in Arizona. Observations indicated that the surface of WJ1 was rich in silica, suggesting a medium-to-high albedo (reflected light). Astronomers used this reflected light to estimate its diameter, which ranges between 40 to 60 cm (16 to 27 inches), solidifying its status as the smallest recorded asteroid.
Denis Vida, an adjunct professor in physics and astronomy at Western, noted, "This is only the sixth asteroid discovered before impact." Utilizing Western's meteor camera network, scientists captured images of the asteroid as it entered the atmosphere above London, Ontario, concluding its descent near St. Catharines. Data modeling from the fireball observations matched estimates from the LDT, resulting in consistent assessments of WJ1's diameter, composition, and orbital trajectory before impact.
"This is only the second time that an asteroid has been meaningfully characterized with telescopes prior to it impacting the Earth," stated Teddy Kareta, a postdoctoral associate at Lowell Observatory. He stressed the importance of collaboration between scientists who are dedicated to protecting Earth against potential impacts. The telescopic and camera data suggest that WJ1 belongs to the S-chondrite category, consisting of stony bodies rich in silica.
Kareta expressed enthusiasm about the study, stating, "This first-ever comparison between telescopic and fireball camera data is extremely exciting, meaning we'll characterize the next asteroid to impact the Earth in even greater detail." Although initial searches in the Niagara region have yielded no findings, residents familiar with meteorite identification continue to look for pieces. Phil McCausland, a Western Earth sciences adjunct professor in the Meteor Physics Group, noted that remnants that fell on land may have blended into the environment over time, but there is still potential for future discoveries.
WJ1 was first identified by the Catalina Sky Survey in Tucson, Arizona, in November 2022. Shortly after, astronomers predicted its impact on Earth within three hours, allowing them to conduct telescopic observations while the asteroid was still in space. This advanced warning facilitated accurate determinations of its entry point over the Great Lakes.
Western physics and astronomy professor Paul Wiegert, a co-author of the study, witnessed the fireball's entry. This event was historic because it was the first time observers were notified in advance to observe a natural fireball.