How can you tell that a star isn't a satellite?

Answer 1

Stars do twinkle--because of their immense distance, only one photon reaches us at a time, and if it is deflected by air currents, we see it blink. Satellites do not twinkle either, because they are even closer. Their brightness will also vary as the satellite changes its aspect to the sun as it orbits the earth. They do not have red and green blinking lights.

Satellites do move, quite quickly. Low orbit satellites orbit the earth every 90 minutes to 2 hours, so they will actually cross the sky in minutes. Geosynchronous satellites are about 150 times farther away (23,000 miles) than low-orbit satellites, and typically are not visible to the naked eye at all. Stars, of course, do not move appreciably.

In short, if you look up just for tonight:

Stars: twinkle and don't move

Satellites: don't twinkle and move like gangbusters.

Answer 2

Satellites move across the sky relative to the background stars which remain fixed relative to each other.

Answer 3

Within a short period of time, minutes, a satellite will move across the sky, whereas a star will appear to be stationary over the same period of time.