Video shows fireball meteor explode in broad daylight. How rare is this cosmic phenomenon?
Fireballs fall on the Earth every day—but the one that just streaked across the southeastern U.S. this week was unlike the rest. Here’s why.
Illustration of a fireball passing in front of the moon as it crosses through Earth's atmosphere. Fireball meteors fall on the Earth every day but it's rare to see one in the daytime.
Illustration by Detlev Van Ravenswaay, Science Photo Library
People across Georgia on Thursday witnessed an unusual flash of light streaking through the bright blue sky, followed by a thunderous boom that rattled windows. But there were no thunderstorms in the area. The culprit? An exceptionally bright meteor called a fireball.
Videos from dashcams and security cameras shared online caught the event, which occurred around 12:25 p.m. EDT on June 26, according to NASA. NASA also confirmed fireball observations from lightning detectors on the National Oceanic and Atmospheric Administration's GOES satellites, as well as meteorite signatures from various doppler weather radars on the ground.
Per a statement from Bill Cooke, who leads the Meteoroid Environment Office at NASA's Marshall Space Flight Center in Alabama, the meteor was an asteroidal fragment that measured three feet in diameter and weighed more than a ton. It was "first seen at an altitude of 48 miles above the town of Oxford, Georgia, moving southwest at 30,000 miles per hour." It then "disintegrated 27 miles above West Forest, Georgia, unleashing an energy of about 20 tons of TNT."
That explosion created sonic booms heard across Georgia, as well as likely meteorite impacts across the state.
The event generated more than 200 reports to the American Meteor Society (AMS), the organization in charge of monitoring meteoritic phenomena, including a possible meteorite strike on a home in Blacksville, Georgia.
But what exactly is a fireball? Here’s why it’s so unusual to see one in the light of day.
Every day, space rocks called meteoroids bombard the Earth. These rocks come from comets, asteroids, or even the moon or other planets and range in size from a speck of dust (most common) to a small asteroid (very rare). NASA estimates some 48.5 tons of meteoritic material enters the atmosphere daily.
However, that’s where the fates of these rocks can diverge. If a meteoroid enters the atmosphere and burns up, it's called a meteor. But if a meteor reaches the surface of Earth, it becomes a meteorite.
Fireballs are a less common type of meteor—they earn that designation when they appear brighter than Venus in the night sky. While thousands of fireballs fall on the Earth each day, most happen over the ocean or uninhabited areas, or they occur during the day and are drowned out by sunlight. That's what makes the Georgia event much rarer.
"Daytime fireballs are rarer to see because the sun outshines the meteor in most cases. Only the largest objects will be seen, and there are fewer of these," says Hankey. According to Hankey, AMS receives reports of daytime fireballs between five and 10 times per year.
Given their larger size, fireballs don’t always burn up completely as they travel through the atmosphere, and their debris will strike the Earth as meteorites. Those meteorites generally cannot be seen for the last nine to 12 miles of their descent—what AWS calls their “dark flight” period—as they lose their light as they decelerate.
(‘Alien’ minerals never found on Earth identified in meteorite.)
As for the window-rattling boom accompanying a fireball, that's likely a sonic boom. Meteors enter the atmosphere at speeds ranging from 20,000 to 160,000 miles per hour. When an object surpasses the speed of sound—around 760 miles an hour at sea level—it builds up so much pressure that this releases a large sound wave as a “sharp release of pressure.”
If you think you've witnessed a fireball, you can submit a report to AMS to help them confirm the event.
"We can usually validate a fireball sighting with five or more eyewitness reports. The data submitted can be mathematically joined, and we can produce a meteor track from the observations," Hankey says.
With 20 or more reports, the team can determine a reasonably accurate track, while videos of a fireball provide even better information. "These can be used to refine the track and gauge the velocity and magnitude," says Hankey. This can help determine whether not the meteor belongs to a meteor shower, or narrow down the area where a meteorite might have fallen.
Editor's note: This story has been updated with a statement from NASA
