We had satellites orbiting that decades ago; right? Probably a transmitter dropped off years ago and "somehow" powered itself up.

Pioneer 10 was the first spacecraft to fly past Jupiter. It was followed by Pioneer 11, Voyager 1 and Voyager 2 flybys. NASA's Galileo mission was first to orbit Jupiter and to send an atmospheric probe into the stormy clouds. The international Ulysses mission used Jupiter's powerful gravity to hurl itself into orbital passes of the Sun's northern and southern poles. Both Cassini and New Horizons studied Jupiter as they hurtled on to their main science targets — Saturn for Cassini and Pluto and the Kuiper Belt for New Horizons.

[link to solarsystem.nasa.gov (secure)]