What was that line of lights in the sky?
If you saw a string of evenly spaced, steady lights gliding across the sky in single file, you almost certainly saw a Starlink train: a batch of SpaceX internet satellites launched together and still bunched up in orbit.
What is a Starlink train?
SpaceX launches its Starlink satellites in batches of around two dozen on a single Falcon 9 rocket, often several times a week. The satellites are released close together in a low orbit, so for the first few days they travel one behind another like beads on a string. They don’t make any light of their own: what you see is sunlight reflecting off their bodies and solar panels.
Why can you only see them for a few days after a launch?
After release, each satellite uses its own thrusters to climb to its working orbit, a trip that takes weeks. As they climb they drift apart, so the tight line gets longer and gappier every night and breaks up within days to a couple of weeks. Once in their working orbits, Starlink satellites are designed and turned to reflect less sunlight, so individually they are much fainter and easy to miss.
Why only around dawn and dusk?
You can only see a satellite when it is lit by the sun while you are standing in darkness. That happens in the hour or two after sunset and before sunrise: the sky is dark where you are, but a few hundred kilometres up the sun is still shining. Later at night, low satellites pass through Earth’s shadow and become invisible. (In summer at high latitudes the sun never gets far below the horizon, so this can happen all night.)
That is also why a Starlink train often seems to switch off one light at a time: each satellite is sliding into Earth’s shadow in turn.
Starlink, ISS, plane, meteor or satellite flare?
- A line of many dots, evenly spaced, following each other along the same path
- A Starlink train, usually within a few days of a launch.
- One very bright, steady light, brighter than any star, crossing the sky in a few minutes
- The International Space Station (or, a little fainter, China’s Tiangong station). Check the pass times for your city.
- A fainter single dot moving steadily across the stars
- An ordinary satellite. Thousands are in orbit, and on a dark night you can usually spot several an hour after dusk.
- Blinking lights, red or green lights, or a white strobe, sometimes with a sound
- An aircraft. Satellites never blink.
- A streak that lasts a second or two
- A meteor (a “shooting star”): a grain of space dust burning up in the atmosphere.
- A steady moving light that suddenly brightens for a few seconds, then fades
- A satellite “flare”: sunlight glinting off a flat panel or antenna. The famous Iridium flares mostly ended when those satellites were retired in 2019, but other satellites still glint.
- A glowing, spreading cloud or “jellyfish” shape shortly after dusk or before dawn
- A rocket launch: the exhaust plume high up is still lit by the sun while the ground is dark.
What to do next
Starlink trains are harder to plan for, because the satellites keep changing their orbits in the first days after launch. The International Space Station is different: its passes can be predicted days ahead, and it is brighter than any Starlink satellite. See when it is visible from where you are:
- New York, NY
- Los Angeles, CA
- Chicago, IL
- Houston, TX
- London, UK
- Toronto, ON
- Sydney, NSW
- Dublin, Ireland
- All cities…
See what is overhead right now — free on iPhone
PERIGEE tracks Starlink satellites, the ISS and thousands of other objects on a live 3D globe, and alerts you before the night’s best ISS pass. It doesn’t forecast Starlink trains, but you can find the Starlink satellites passing over you on the globe.
Open the live 3D viewFrequently asked questions
What is a Starlink train?
A batch of SpaceX Starlink internet satellites that were launched together on one rocket. For the first few days after launch they fly one behind another in a tight line, and sunlight reflecting off them makes the line visible from the ground as a string of moving dots.
How long after a launch can you see a Starlink train?
Usually for a few days, sometimes a week or two. The satellites use their thrusters to climb to their working orbits, and as they climb they spread out along the orbit, so the line gets longer, gappier and fainter each night until it is gone.
Why did the lights disappear one by one?
Satellites don’t make their own light; they shine only while sunlight is hitting them. Each satellite in the line slides into Earth’s shadow in turn, so the lights go out one after another, all at the same spot in the sky.
How can I tell Starlink satellites from the ISS?
A Starlink train is many dots in single file. The ISS is a single, very bright, steady light — brighter than any star — that takes a few minutes to cross the sky. Neither one blinks; blinking or colored lights mean an aircraft.