An iridescent streak lit up the sky over Southern California on Friday night, stopping traffic and leading some residents to marvel and others to worry about a UFO or even a nuclear bomb attack. In reality, it was a SpaceX rocket lifting off from Vandenberg Air Force Base, north of Santa Barbara, Calif., carrying 10 satellites for the Iridium constellation. They will be used in mobile voice and data communications.

In a bid to ease the minds of worried witnesses, the Los Angeles Fire Department released a statement saying the "mysterious light in the sky is reported to be the result of [Vandenberg] Air Force Base launching rocket to put satellite into space."

SpaceX CEO Elon Musk didn't help matters when he tweeted, "Nuclear alien UFO from North Korea."

The glowing contrail could be seen as far away as Phoenix, reports The Associated Press.

"People were wondering if it had something to do with movies, or TV or a UFO," Jimmy Golen, who was touring the Warner Bros. studio in Burbank at the time, told the wire service.

Despite the confusion, Friday's launch was not a novelty. It was one of more than a dozen launches SpaceX has completed this year from California as well as Cape Canaveral, Fla., for various missions including sending supplies to the International Space Station.

The AP reports Friday's launch was perhaps especially dramatic since it occurred during sunset, helping illuminate the contrail.

In another tantalizing move Friday, Musk posted a series of pictures to Instagram of an original Tesla Roadster to be used in a test flight of a brand new rocket.

"Test flights of new rockets usually contain mass simulators in the form of concrete or steel blocks. That seemed extremely boring," Musk wrote. "So we decided to send something unusual."

Musk released the images hours after an apparently leaked photo of the roadster was posted to Reddit, according to Gizmodo.

The Falcon Heavy's inaugural flight is expected to take place next month, reports

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