Satellites in the night sky

What a satellite looks like

Look up on a clear evening and you may notice a star that moves. It glides at a steady pace, does not flash and often fades out partway across the sky. That is almost certainly a satellite reflecting sunlight.

Satellites have no lights bright enough to see from the ground. You see them because they are high enough to be in sunshine while you are already in darkness. Planes, by contrast, carry blinking red, green and white lights, and meteors streak by in a second or less.

When and where to look

The best window is roughly one to two hours after sunset and before sunrise. Later in the night, most low satellites pass into Earth's shadow and vanish. Around midsummer at mid-latitudes, the Sun stays not far below the horizon all night, so satellites can be seen for longer.

You need no equipment. Find a dark spot, give your eyes some time and scan the whole sky. On a good evening from a dark site you may count a dozen or more.

A satellite that suddenly dims and disappears has entered Earth's shadow. That moment is a nice reminder that you are watching an object in orbit, not something in the air.

Spotting the ISS

The International Space Station orbits at about 250 miles and circles Earth about every 90 minutes. With its huge solar panels it is the brightest satellite, often outshining every star and rivaling Venus.

Its passes are predictable to the minute. NASA's Spot the Station service and satellite-tracking apps list times, the direction it appears from and how high it will climb. A good pass lasts about four to six minutes.

Through binoculars you may glimpse its elongated shape, but it moves fast. Photographers often capture it as a bright line with a camera on a tripod and a long exposure.

Starlink trains and flares

Shortly after a launch, Starlink satellites travel in a tight row before spreading out and climbing to their working orbits. For a few days they can look like a string of pearls crossing the sky. Trackers publish predictions for these trains, but they fade as the satellites rise and turn.

Satellite flares were brief, brilliant flashes caused by sunlight bouncing off flat panels. The best-known came from the first generation of Iridium communication satellites, which could flash brighter than Venus. Those satellites were retired by 2019, so such flares are now rare.

Many satellites tumble or rotate, so their brightness can rise and fall as they cross. A satellite that pulses regularly is usually spinning.

How satellite constellations affect astronomy

A satellite constellation is a large group of satellites working together, mostly for internet service. As of 2026, Starlink has more than 10,000 satellites in orbit, and other companies are launching their own networks. The total number of active satellites has grown many times over since 2019.

For professional astronomers, the problem is streaks: bright lines across images, especially in wide-field surveys taken around twilight. Radio telescopes face interference from satellite transmissions. Many trails also add to the general brightness of the night sky.

The International Astronomical Union set up a centre in 2022 to protect dark and quiet skies. It works with satellite operators on darker coatings, sun shades, orientation changes and sharing orbit data, so observatories can avoid or remove trails. Some designs are now dimmer, but the issue remains open.

Tips for watching

Check a prediction website for the ISS and other bright satellites, and note the start direction. Lie back on a reclining chair to take in more sky. Avoid looking at bright phone screens, or use a red-light mode.

If you photograph the sky, satellite trails will appear in long exposures. Taking several shorter shots and stacking them with software that rejects trails can clean up your images.