A row of bright, evenly spaced lights glides silently across the evening sky, one behind another, then fades out. Every time it happens, local news and social media fill with questions about UFOs. In most cases the answer is simple: it is a train of Starlink satellites, a few days after launch. This article explains what you are seeing and why it looks so unusual.
Starlink is a satellite internet network operated by SpaceX. The first batch of 60 satellites was launched in May 2019, and launches have continued ever since, usually dozens of satellites at a time on a Falcon 9 rocket. Public trackers now count roughly ten thousand or more Starlink satellites in orbit, making it by far the largest satellite constellation ever built. Exact numbers change almost daily with launches and re-entries, so treat any single figure as approximate.
Because the satellites are so numerous and fly low, they are now among the most common objects people notice in the night sky.
After a launch, the satellites are released close together and only gradually spread out. For the first days they travel in nearly the same orbit, a few tens of kilometers apart, and from the ground they look like a string of pearls moving in single file. Observers often report 20 or more lights in a row, all the same brightness, all following the same track.
That regular spacing is exactly what makes the sight feel artificial. Natural objects such as meteors or planets do not travel in neat convoys. But the explanation is mundane: the satellites are simply still close to where the rocket let them go.
Satellites make no light of their own. You see them because they reflect sunlight. Starlink satellites orbit a few hundred kilometers up, so they can still be lit by the Sun after it has set for observers on the ground. This is why trains appear shortly after sunset or before sunrise, when the sky is dark but the satellites are still in sunlight.
Later in the night, the satellites pass into Earth's shadow and vanish. Sometimes a train seems to switch off in the middle of the sky. That is not a ship departing; it is the satellites entering the shadow.
Newly launched satellites are placed in a low parking orbit and then raise themselves to their operating altitude, which for most Starlink satellites is around 550 km. As they climb and disperse, the line breaks up and the lights become fainter. Observers typically describe the best viewing as lasting for a few days after a launch, though the exact window depends on the mission. After that, individual satellites are still visible, but as separate faint dots rather than a convoy.
Brightness matters too. Early reports from astronomers described satellites at around 2nd or 3rd magnitude in their low orbit, bright enough to be easy to spot, and fainter, around magnitude 4 to 5, once at operating altitude. SpaceX later tested darker coatings and sunshades (the "DarkSat" and "VisorSat" designs) to reduce the glare, though astronomers say the satellites remain a concern for telescopes.
The same logic applies to other lights people report. Planets, bright stars, aircraft, balloons and drones are all common explanations, as we discuss in UFO Sightings Explained: What Are UAPs?. If you are unsure what a light in the sky might be, our guide to the difference between asteroids, comets and meteors also helps separate natural objects from artificial ones.
Satellite trains are more than a curiosity. Astronomers have raised concerns that bright satellite streaks can cross telescope images, especially wide-field surveys that search for faint, fast-moving objects. Those same surveys are the backbone of asteroid discovery, which we describe in how NASA tracks asteroids. Scientists, satellite operators and groups such as the International Astronomical Union have been discussing ways to reduce the effect, including darker surfaces and software that removes streaks from images.