They are powered by solar electricity that is saved in batteries. But to actually move you need something to throw out. That can be many things, anything from normal water, metal or noble gases.

Starlink initially used Krypton for its thrusters. But they have now switched to Argon since its incredibly cheap and available. Xenon for a long time was the standard, but its to expensive and rare.

Some sats also have chemical power, often a Hypergolic propellant, like dinitrogen tetroxide plus hydrazine. Specially for larger sats this is the case.

- https://en.wikipedia.org/wiki/Ion_thruster

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