The “big boom” heard throughout the greater Shenandoah County region Friday was a bolide, according to the National Aeronautics and Space Administration.
A bolide is another term for a fireball, a meteor that enters the Earth’s atmosphere, burns brighter than the planet Venus, and then explodes — possibly creating meteorites, according to William Cooke, lead of NASA’s meteor office.
“...It generates a bunch of excitement,” Cooke said, when the event occurs over a populated area.
According to NASA’s Facebook Page, “NASA Meteor Watch” a strong fireball-like signature showed up on satellite mapping data at 10:24 a.m. Friday.
Because of cloud cover, no camera imagery of the event was available, the page posted. But the satellite mapping data put the bolide west of Luray along the West Virginia and Virginia borders.
The explosion was the equivalent of one and two tons of TNT, Cooke said. Judging by the explosion size the object most likely had a mass of around 50 pounds, assuming a typical speed of 45,000 miles per hour, the page posted.
It’s unclear where the bolide originated, but they can sometimes come from asteroids colliding in space, causing fragments of rock to break off and enter the Earth’s atmosphere, Cooke said.
Mike Hankey, with the American Meteoric Society, said the cause of the fireball was a fragment of an asteroid that collided with the Earth’s atmosphere.
“It was large enough to penetrate deep into the atmosphere causing the boom/shake,” Hankey said.
The American Meteor Society has an online fireball reporting database, which recorded 25 witnesses to the event as of Monday afternoon.
A little more than half saw what happened from West Virginia, one caught a glimpse from Pennsylvania and the rest were from the Luray and New Market region.
Greg Redfern, an author and WTOP space reporter based in Charlottesville who has been collecting meteorites for over 20 years, called the event a bolide.
Because of the pressure of the atmosphere building up against the fireball as it falls, it explodes, breaking into pieces, Redfern said. The fireball is what the witnesses saw, and the “big boom” was the explosion, Redfern said.
If there hadn’t been so much cloud cover Friday morning, there would have been more witnesses, Redfern said. The bolide’s elevation was likely about 316,800 feet and traveling at a rate of 12 or 15 miles per second from the north to the south, Redfern said he estimated. It could’ve been about 10-feet long, Redfern guessed.
“This was not a big bolide, but this was a bolide,” Redfern said.
Meteorites, or pieces of the meteor created after it exploded, could have fallen in the location of the bolide, but often will get pushed by winds a few miles away, Cooke said. Meteorite hunters will use weather doppler technology to identify where the meteorites may have fallen.
Fireballs are seen all the time and are very common, but the ones that produce meteorites are much more rare, “...about one per month in North America,” Cooke said.
If there are meteorites, the rocks will be a glossy black, Redfern said. They will likely weigh a few ounces, not cause a crater and will be resting on the ground, Cooke said. They will not be flaming, as they do in the movies, Cooke said.
Although there could be meteorites from Friday’s event, no findings have been reported, Cooke said.
In order for a rock to be confirmed as a meteorite, Redfern and Cooke said it must be tested with the Meteoritical Society, an international organization.
By law, the meteor belongs to the owner of the property on which it falls, not who discovers it, Cooke said. Anyone who finds what they think is a meteorite should contact a local meteorite “hunter” or a geologist at a local university, Cooke said.
Hankey said a database of all known meteorites shows that Virginia has seen 18. The last two were found in Lorton in 2010 and Keen Mountain in 1950, Hankey said.
An iron meteorite hit Staunton in 1869, according to Redfern.
“So two VA meteorites in the last 71 years, ” Hankey stated by email. “Likely three to five meteorites fall in the state per year, but it is difficult to find them.”