This sound graph from the U.S. Geological Survey's Lakeview Retreat near Centreville, Ala., shows a loud boom heard over Alabama
at about 1:39 p.m. CST. The cause of the boom is still unknown. (NASA)
NASA scientists in Huntsville, Ala., said Tuesday night that the origin of a mysterious boom that rocked central Alabama earlier Tuesday "remains unclear." The evidence so far is pointing toward a large meteor or some kind of supersonic aircraft.
The sound was reported to multiple Birmingham area law enforcement agencies and to officials in Arab, Anniston, Hayden, Kimberly, Center Point, Jasper and Gardendale, among other places.
Bill Cooke, head of NASA's Meteroid Environment Office at the Marshall Space Flight Center, released what the office knows so far Tuesday night.
1. Seismic data from the U.S. Geological Survey's Lakeview Retreat near Centreville, Ala., show "a fairly loud boom occurring on or before 1:39 p.m. CST."
2. The Elginfield Infrasound Array in southern Ontario 600 miles from north Alabama "picked up a matching infrasound signal beginning at 2:02 p.m. and lasting around 10 minutes." NASA said the signal "could have been generated by a bolide, larger supersonic aircraft or a ground explosion." A bolide is a large meteor that explodes in the atmosphere.
3. Eyewitnesses reported a vapor trail, and NASA said that points to a meteor or aircraft.
The sound wasn't caused by a Leonid meteor, NASA said. The Leonid meteor shower is occurring this month, but Leonid meteors are small and never penetrate low enough into the atmosphere to produce sounds audible on the ground.
NASA says its scientists will look for new data Wednesday to better "characterize the energy of the event." That may provide more clues to its origin.