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Can artificial satellites be seen with the unaided eye?

Most definitely they can! In fact, many people are surprised that an object orbiting hundreds of miles above our heads can be readily seen without the use of binoculars or a telescope.

From the launch of the first Sputnik in 1957 to the present, the number of satellites in space has grown at a spectacular rate - there are now more than 10,000 good-sized hunks of metal orbiting the Earth, though not all are functional satellites. In fact, the total number of active satellites is about 600. From the days of the old Soviet Union, countless hundreds of discarded rocket casings and cylinders from their Kosmos program alone were left in orbit. Some of these can shine like a moderately bright star.

British astronomer Desmond King-Hele once noted that a satellite "looks like a star that has taken leave of its senses and decided to move off to another part of the sky."

If you go out and carefully study the sky near dusk or dawn, the odds are that you should not have to wait more than 15 minutes before you see a satellite. Most are too faint to be seen with the unaided eye. But a few hundred are large enough (over 20 feet in length) and low enough (100 to 400 miles, or 160 to 640 kilometers above Earth) to be visible.

Satellites are seen at night because they are illuminated by the Sun. A satellite entering the Earth's shadow immediately vanishes from view and pursues an unseen path until it again emerges into full sunlight.

The International Space Station ("Alpha") and the Space Shuttle are by far the brightest. Orbiting the Earth at an average altitude of 240 miles (380 kilometers), they can appear to move as fast as a high-flying airliner; sometimes taking about three to four minutes to cross the sky. They can easily be confused with aircraft lights, though at their brightest they can sometimes appear to rival Jupiter in brilliance. [Satellite Spotting Guide]

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