When SpaceX launched a rocket carrying an Argentinian Earth-observation satellite from California, both the night sky and social media lit up.

People as far away as Phoenix and Sacramento posted photos of the space launch on Sunday night. It was the first time SpaceX landed a first-stage booster back at its launch site at Vandenberg Air Force Base, about 130 miles (209 kilometers) northwest of Los Angeles.

In this image made from video provided by SpaceX, a SpaceX Falcon 9 rocket carrying an Argentinian satellite blasts off from the Vandenberg Air Force Base launch site, about 130 miles (209 kilometers) northwest of Los Angeles on Sunday, Oct. 7, 2018. The primary purpose of the mission was to place the SAOCOM 1A satellite into orbit, but SpaceX also wanted to expand its recovery of first stages to its launch site at the Air Force base (SpaceX via AP)

The Air Force warned residents on the central California coast they might see multiple engine burns by the first stage and hear one or more sonic booms as it returned.

But many were taken by surprise when the launch illuminated the sky, wondering what the otherworldly-looking site was. Some speculated it was a comet or an alien aircraft.

Source: The Associated Press