SAN FRANCISCO -- It wasn't a bird, plane or Superman, but there was a blue light streaking across the sky Saturday night, visible for hundreds of miles across the U.S. Southwest. Though some thought the light may have been a meteor shower or a UFO, it was actually a missile test by the U.S. Navy. 

The streaking light, which has also been described as some as green, was the result of a rocket fired from a submarine, according to several reports. The Navy said the missile was part of a planned test flight but that it was not armed, according to CBS Los Angeles. Accordong to the NASASpaceFlight Twitter, it was a Trident II missile test-fired by the sub USS Kentucky.

Social media users in California and Arizona captured many photos and videos of the blue streak: