Starlink train: what it is and when you can see it
A line of lights moving across the night sky is usually a fresh batch of Starlink satellites. Why they travel in a line, how long it lasts, and how to catch one.
What you are seeing
SpaceX launches Starlink internet satellites in batches of a few dozen. Right after release they fly one behind the other in the same orbit, so from the ground they look like a string of pearls sliding across the sky. People often mistake it for a UFO.
Why it only lasts a few days
After launch the satellites slowly raise their orbits with their own thrusters and spread apart. The tight line is easiest to see in the first days after a launch and becomes a loose scatter, then disappears into the constellation, within one to a few weeks.
Once in their working orbit the satellites are also turned to reflect less sunlight, so a single Starlink is much fainter than a fresh train.
How to catch one
- Watch the launch schedule: a train is only possible in the days after a Starlink launch.
- Like the ISS, the satellites are only visible when your sky is dark but they are still in sunlight, so look in the hours after sunset or before sunrise.
- Check passes for the new satellites over your location; the first satellite of the train leads the others by seconds to minutes.
- Have a wide view of the sky: the line can stretch across a large part of it.
Is it harmful?
Not to people watching. Astronomers are concerned that tens of thousands of satellites leave streaks in telescope images, which is why operators have worked on darker coatings and sunshades.