Astronaut Kathy Thornton jettisons a damaged solar array panel into space during Hubble's first servicing mission in 1993. When the solar panels were replaced, astronauts found a bend in the casing of this panel. The panel couldn't be returned safely to Earth, and was released into space. Eventually the panel will descend into Earth's atmosphere, where the friction created by the speed of its fall will burn it up, turning it into a shooting star.
Hubble's solar panels generate power for the telescope by converting sunlight into electricity. The arrays power the telescope and charge its batteries while Hubble is in sunlight. When Hubble moves into the dark portion of its orbit, the batteries provide power.