Late Friday afternoon ahead of a holiday weekend, social media lit up with posts about a mysterious object flying through the skies above Los Angeles. Was it a UFO? A chemtrail? Superman? Nope — it's the launch of a SpaceX Falcon 9 rocket, Iridium-4.

Jill Replogle tweet

Vandenberg Air Force Base confirmed that the massive glowing cloud and floating orbs over L.A. was the SpaceX rocket, launched at 5:27 p.m.

So what makes it look like that? Astronomer Jonathan McDowell offered this explanation:

SpaceX rocket appearance

It's the fourth set of 10 satellites in a series of 75 total that SpaceX is launching as part of Iridium NEXT, according to the organization. These satellites are replacing an existing network of low-Earth orbit commercial satellites.

Video of SpaceX flying overhead

They also reused the first stage for this launch from the Iridium-2 mission, though they noted that they don't plan to recover the first stage from this launch.

Watch the full launch video here:

Full SpaceX launch video

This story has been updated.