A handheld video filmed in Japan has captured dozens of Starlink satellites crossing the night sky in one tight, perfectly straight line. They look like evenly spaced bright points gliding silently overhead, and it is easy to see why a sight like this makes people stop and stare. The glow is sunlight reflecting off the satellites, which can be seen from the dark ground below shortly after sunset or before sunrise. This formation is known as a Starlink "train," and in this case it has been correctly identified rather than mistaken for something stranger.

These trains appear when newly launched Starlink satellites are still clustered together in low orbit after being deployed from a SpaceX Falcon 9 rocket. As the satellites move toward their working orbits over the following days and weeks, they spread out and become far less noticeable. Sightings like this have become common around the world because SpaceX keeps building up its constellation, which now numbers in the thousands, to deliver broadband internet. The growing number of satellites has also raised questions among astronomers and skywatchers about how much they brighten the night sky. For anyone who spots a glowing line crossing the heavens, the answer is usually not a mystery but a fresh batch of satellites on their way up.