On Tuesday night, the sky over southeast Michigan lit up with a dazzling flash, a loud boom resounded and the ground trembled. Some locals wondered whether the region had been hit by a freak lightning strike, a bomb or even a UFO. But as Lindsey Bever of the Washington Post reports, it was soon determined that the cause of the mysterious flash was a rare astronomical phenomenon: a meteor exploding in Earth’s atmosphere with a fiery blast.
“[T]his was a very slow moving meteor — speed of about 28,000 miles per hour,” NASA’s Meteor Watch writes on its Facebook page. “This fact, combined with the brightness of the meteor (which suggests a fairly big space rock at least a yard across), shows that the object penetrated deep into the atmosphere before it broke apart (which produced the sounds heard by many observers).”
The United States Geological Survey confirmed that a meteor had fallen and reported that the blast had caused vibrations that registered as a magnitude 2.0 event centered about 5 miles from New Haven, Michigan according to Karma Allen of ABC News. But the brilliant fireball was observed across six states and in Canada.
Meteors are “bits of interplanetary material” that penetrate the Earth’s atmosphere and are heated to incandescence by friction, as NASA explains. (The objects are called “meteoroids” as they fly through space, becoming meteors only as they burn up in the sky.) Meteors enter the atmosphere at least once a month, Bill Cooke, lead for NASA’s Meteoroid Environment Office at the Marshall Space Flight Center in Alabama, tells Bever. But he notes that it is “very rare” for the objects to produce a fireball that is observed by so many people. Most often, bright-burning meteors either break up over sparsely populated areas, are masked by the sun or fall late at night when most people are asleep.
Those lucky enough to observe the unusual event were suitably awed. “All of the sudden, the whole yard started getting brighter, kind of yellowish-orange, like a flashbulb, then got black,” Michigan resident Mike Tarkowski tells Mark Hicks of the Detroit News. “It was something big and it was something up in the air.”
The NASA Meteor Watch notes in its Facebook post that the explosion likely produced meteorites—chunks of interplanetary rock and metal that survive the atmospheric plunge and fall to the ground.
“Pieces of an asteroid lying near Detroit?” the group writes. “Let’s see what the meteorite hunters find.”
Editor's Note, January 18, 2018: This article has been updated to clarify that the meteor blast didn't cause a true earthquake, but rather vibrations in the ground that registered as a 2.0 magnitude event.