Yes, it pays to watch the sky. This morning, Sept. 9th, with no warning whatsoever, a flurry of bright fireballs appeared over eastern parts of the United States. "Our SENTINEL all-sky camera picked up 25 bright meteors in a shower that began at 0620 UT and lasted approximately 4 hours," reports NASA astronomer Bill Cooke of the Marshall Space Flight Center in Huntsville, Alabama. This video "frame-stack" shows the outburst at a glance:

fireball outburst

"Most appear to have a radiant near Perseus (3.3h, +43o), leading us to hypothesize an outburst of the September Perseids," says Cooke. Also known as the delta-Aurigids, the September Perseids come from an unknown comet and have been caught bursting only four times in the last century: 1936, 1986, 1994 and now 2008. Most of the meteors recorded by the NASA camera were magnitude -2 or brighter, i.e., as bright as Jupiter or Venus.

"We encourage people to keep an eye on the sky tonight," says Cooke. "The outburst is almost certainly over, but we don't know enough about these mysterious meteors to say for sure." Stay tuned for updates.