Starlink train: a row of lights in the sky
One of the most widely reported sightings of recent years: a row of evenly spaced white points moving in a straight line across the sky. Almost certainly a Starlink train from SpaceX — but Sky Lens can confirm it from live orbital data for your exact location and time.
SpaceX is building a mega-constellation of satellites to deliver global broadband internet from low Earth orbit (LEO). The scale of this project is unprecedented in the history of spaceflight.
Mass launches
SpaceX launches batches of typically 20–60 satellites at a time on a Falcon 9 or Starship. After launch they fly close together in formation at an initial altitude of ~340 km — this is the visible 'train'. They then climb to their operational altitude over the following weeks.
Operational altitude
After the first 1–4 weeks the satellites reach their operational altitude of ~550 km and spread out along their orbit. At this altitude they are individually visible as fairly bright, steadily moving points — no longer recognisable as a train.
Constellation scale
More than 6,000 Starlink satellites are now in orbit. SpaceX has applied for approval to eventually operate 42,000. At any given moment dozens of Starlink satellites are overhead, but only a few per pass are bright enough to see with the naked eye.
Impact on the sky
Astronomers are concerned about the effect on astronomical observations. SpaceX has been working on 'visorsat' sun shields to reduce satellite brightness. Brightness varies considerably by model and orientation relative to the sun.
The following characteristics together make a Starlink train uniquely recognisable. No other object in the sky shows the same combination.
Pattern
5–20 evenly spaced points on a straight line. The spacing is uniform — like lights on a taut string. Aircraft always fly alone.
Movement
Moves in a perfectly straight arc across the sky. No turns, no wobble. Typically travels west to east or southwest to northeast, depending on the inclination of the orbit.
Speed
~7 km/s orbital speed — noticeably fast across the sky. A full horizon-to-horizon pass takes 2–6 minutes depending on the maximum elevation angle above your location.
Light character
No flicker — steady, constant light. Brightness can vary as the satellites rotate (orientation effect), but there is never a rhythmic strobe like an aircraft's.
Sound
Completely silent. If you see a row of lights moving steadily across the sky in silence — that is strong evidence for satellites and against aircraft or drones.
Colour
Bright white. No colour change, no red or green. Stars low on the horizon do flicker red and blue (scintillation), but Starlink satellites pass high enough to avoid that effect.
The visibility window is limited — you cannot see Starlink in the middle of the night. The geometry of the sun, Earth, and satellite must align.
Twilight required
Satellites are only visible when they are themselves in sunlight but the ground below is already dark. This gives a window of 30–90 minutes after sunset and 30–90 minutes before sunrise. During the day they are lost in ambient light; in the middle of the night they are in Earth's shadow.
Pass times shift daily
Exact pass times vary each day at any given location. A satellite visible tonight at 21:04 will be visible tomorrow at roughly 21:19 (the orbit shifts ~15 minutes per day). Sky Lens calculates this exactly for your coordinates.
Seasonal variation
In summer, when nights are short, satellites can sometimes be seen late into the evening because the sun has not dropped far enough below the horizon. In winter the window arrives earlier but closes sooner.
Cloud cover
Cloud cover completely blocks the view of satellites. Sky Lens shows the cloud cover percentage at the time of your sighting so you know whether it was physically possible to see the satellite.
Sky Lens has real-time access to TLE orbital data (Two-Line Element sets) for more than 14,000 objects in Earth orbit, updated several times a day.
Orbital calculation
Sky Lens calculates the precise position of every known satellite at any requested time via the Skyfield library. For Starlink, all 6,000+ active satellites are included in the calculation.
Position and angle
For your location and time, Sky Lens determines which satellites were above the horizon, at what elevation angle, in which direction they were moving, and how bright they were (based on distance and solar geometry).
Candidate list
If Starlink satellites match your description (direction, elevation, heading, time), they appear at the top of the probability list — with the calculated elevation angle and direction as supporting evidence.
Enter your location and the time of the sighting. Sky Lens calculates which Starlink satellites were overhead at that moment and gives you their exact elevation angle and direction.