Strangest fact
On the video, the dots seem to react to the flash all at once, as if something had signaled them. That looks deliberate, which is why the clip is still shared more than 30 years later.
STS-48 was a five-day Space Shuttle Discovery mission in September 1991 that put the Upper Atmosphere Research Satellite into orbit. On September 15, a camera in the payload bay, looking out toward the Earth's horizon, recorded several small points of light moving slowly across the view.
Partway through the clip there is a flash near the bottom of the frame. Right after it, several of the dots change direction, and one appears to shoot away quickly. The clip was later shown on television and online as evidence of objects moving under intelligent control, and some researchers argued the shuttle's attitude did not change, so no thruster could have fired.
NASA's explanation is that the dots are small particles near the shuttle, such as ice and bits of insulation, lit by the Sun, and that the flash was a small steering thruster firing. Its exhaust pushed the nearby particles onto new paths. The former NASA engineer James Oberg, interviewed by Atlas Obscura in 2016, pointed out that anything that stays in a shuttle camera's view for long has to be moving with the shuttle at about 17,500 miles per hour, which means it almost certainly came from the shuttle. He calls this debris space dandruff.
The astronomer Phil Plait reached the same conclusion in his 2002 book Bad Astronomy. Because the points are only dots, no one can say exactly what each one is.