CHICAGO — A dazzling blue-green flash that lit up the pre-dawn sky across much of the Midwest Friday was a fireball burning up as it entered Earth's atmosphere, an astronomer said.
"That blue-green flash was a fireball, and anyone who saw it, well, that was great, because as long as I've been here I've never seen one. They're fairly rare," said April Whitt, an astronomer at the Adler Planetarium.
A fireball is similar to a meteor, Whitt said, except that fireballs are made up of larger particles, pebble-sized rather than dust-sized.
Dozens of people in Illinois, Michigan, Kentucky and Ohio called police departments, radio stations and the planetarium after witnessing the flash at about 5 a.m.
William Spencer of Southfield, a Detroit suburb, said that he saw the light on his way to work.
"It was a big bluish-green ball of light and it had a train of yellow sparks behind it," he said. "I thought it was a helicopter, it was moving fast . . . . Then it just disappeared. I thought it had crashed."