| Flagstaff, AZ — In an international study led by Lowell Observatory’s Dr. Teddy Kareta and published today in The Planetary Science Journal, scientists take a pioneering, integrative approach in studying near-Earth asteroids (NEA). By comparing Arizona-based telescopic observations of the asteroid 2022 WJ1 to video captured by a network of meteor observing cameras in Ontario, Canada, they determine the body’s composition and size before it fractured upon entering Earth’s atmosphere. The study is significant for not only characterizing Asteroid 2022 WJ1—the smallest asteroid in space to be thus characterized —but also for establishing the methodology for studying other potential Earth impacting bodies. This is the first time the two techniques have been used to study the same object.
The size of Asteroid 2022 WJ1 is determined telescopically, with the 4.3-meter Lowell Discovery Telescope (LDT). Observations from the LDT indicate that the surface of Asteroid 2022 WJ1 is rich in silicate minerals (like pyroxene and olivine), meaning it reflects about 20-30% of the sunlight that hits its surface. From this, astronomers calculate the asteroid had a diameter in the range of 40-60 cm (16-27 inches), making it one of the smallest on record.
Kareta says, “This is only the second time that an asteroid has been meaningfully characterized with telescopes prior to it impacting the Earth. It’s a testament to our good luck and preparation, but it’s also due to the community that cares about keeping the Earth safe from these impactors learning to work together better.”
Using their network of meteor observing cameras in the vicinity of London, Ontario, Western University scientists imaged the asteroid as it entered into and broke apart in Earth’s atmosphere. Modeling how the asteroid fragmented and how large it was prior to burning up above Toronto agrees with the telescopic LDT-based diameter.
The telescopic and fireball camera data both suggest Asteroid 2022 WJ1 fits into the S-type category of asteroids. These are stony bodies rich in silicate minerals (thus the “S” designation). They are among the oldest bodies in the solar system and comprise the most common type of meteorite, known as ordinary chondrites, to hit Earth. “This first-ever comparison between telescopic and fireball camera data is extremely exciting, and means we’ll be able to characterize the next asteroid to impact the Earth in even better detail,” adds Kareta.
Likely, not all the fragments burned up in Earth’s atmosphere. While some searches for meteorite pieces have been attempted, none have been found. Much of the predicted fall area is under water. For the fall area on land, Western team member Dr. Denis Vida says, “We have no plans to do any official searching. Two years on, any meteorites that fell on land will have blended in with the landscape.” That said, those in the area may still get lucky and find a meteorite or two in the coming months and years.
Asteroid 2022 WJ1 was discovered by the Catalina Sky Survey in Tucson, Arizona, in November 2022. Astronomers soon predicted that the object would impact Earth within three hours. This allowed just enough time for scientists to telescopically observe the object while it was still in space. This also gave astronomers time to gather more astrometric data (a celestial body’s precise position and motion) of the asteroid to refine its orbit. This allowed for a more accurate determination of where the body would enter Earth’s atmosphere—over the Great Lakes, on the border of the United States and Canada. The predicted impact site proved fortuitous, since Western happens to operate one of the world’s foremost networks of meteor observing cameras.
The LDT, near Flagstaff, Arizona, was ideal for telescope viewing. Its capacity for rapid and stable tracking meant it can keep up with small and fast-moving NEAs. Kareta, who just happened to be scheduled to observe with the LDT that night, imaged the asteroid with his team for about one hour before it was lost in the shadow of Earth. He says, “At the time that we lost the asteroid—when it got too dim to be seen in our images—we had the telescope moving at five degrees per second to try to keep up with it. That’s fast enough that most other telescopes would have had to give up considerably earlier.”
Dr. Gerard van Belle, Director of Science at Lowell Observatory, says, “Because of the wide-ranging capabilities of the LDT, we were able to quickly acquire the asteroid and continue to observe it as it streaked across the sky. We are pleased that the telescope is as good as it is and are excited to be making it even better with our new Science Vision plan that will allow it see faster, fainter, and farther.”
Kareta adds, “It’s tremendously fortuitous that this asteroid happened to fly over Arizona’s dark skies at night before burning up over Western’s excellent camera network—it’s hard to imagine better circumstances to do this kind of research.” |
