Just before 10 P.M. local time on Feb. 28, a dazzlingly bright meteor traversed the U.K.'s western sky, glowing for about six seconds. It was so bright, in fact, it was termed a fireball. Hundreds of people who happened to glimpse the sight took to social media to report what they saw, wondering if their eyes had been playing tricks on them — or even if they had just seen a visitor from outer space.
But for astronomers, this was a special and rare treat for another reason: It was a chance to search for any pieces left behind.
From meteor to meteorite
We are all familiar with meteors — the flashes of light produced when a piece of rock or dust from space burns up in our atmosphere. Maybe you’ve even enjoyed watching meteor showers throughout the year. But fireballs are rarer. These exceptionally bright meteors streak across the sky with a magnitude greater than –4. That’s about as bright as Venus at its best.
If a meteor doesn’t completely burn up on entry, anything left falls to Earth as a meteorite. Like the larger space rocks that spawn them, meteorites range widely in size. The 1920 meteorite that landed in Hoba, Namibia, for instance, weighs 66 tons (60 metric tons), while the 1949 Beddgelert meteorite that landed in North Wales in the U.K. weighs only 28 ounces (794 grams). But every piece, no matter how small, tells a unique story.
Catching the fall
Of the approximately 65,000 known meteorites, only 1,206 were seen falling to Earth.
To increase this number, the Natural History Museum in London leads and operates the U.K. Fireball Alliance (UKFAll), which employs a huge network of cameras aimed at the skies above the U.K., recording the bright streaks these rocky fragments leave behind. The pictures taken as part of this project provide vital information about the paths these rocks take through our atmosphere. By comparing images taken from different locations, observers can trace the meteors path to help deduce where surviving fragments may have landed. And using this technique, UKFAll aims to recover such meteorites.
Led by volunteers and staff at the Natural History Museum London, UKFAll is a collaboration between six key camera networks: five operate in the U.K. and Europe, while a sixth spans the globe. Thanks to this collaboration, UKFAll was able to calculate where pieces of the most recent U.K. fireball might have landed, as well as determine where in the asteroid belt the original space rock came from, based on its trajectory when entering the atmosphere.
On the night of the fireball, over a thousand reports came filtering into the U.K. Meteor Observing Network (UKMON), part of UKFAll’s network. These were a mixture of eyewitness reports, footage from doorbell cameras, and photographs. Dedicated UKMON cameras captured this unexpected visitor, too.
When footage showed the fireball fragmenting, hopes were high that some material would be found on the ground. Using information from this network of cameras and footage from the public, UKFAll recreated the fireball’s flight path to determine possible landing sites in Gloucestershire. Mary McIntyre, an active UKMON participant, tells Astronomy, “This is a huge win for citizen science in that so many cameras caught the event across so many networks, and everybody worked together quickly to calculate the strewn field [the area where debris might have landed].”