Reusable Falcon 9 lights up the sky

VANDENBERG AIR FORCE BASE, California - Many people pulled their cars over to take photos and videos of the sight. Witnesses posted their photos on social media, with many wondering if it was an unidentified flying object.

In June, the Falcon 9's first stage was used to send 10 satellites for Iridium Communications Inc's next-generation global satellite constellation, Iridium Next, which will ultimately include 81 satellites.

"It was definitely aliens," SpaceX founder Elon Musk joked on Twitter, responding to one person who said the launch sparked an "alien debate".