Jupiter’s mysterious X-ray auroras have been explained, ending a 40-year quest for an answer. For the first time, astronomers have seen the way Jupiter’s magnetic field is compressed, which heats the particles and directs them along the magnetic field lines down into the atmosphere of Jupiter, sparking the X-ray aurora. The connection was made by combining in-situ data from NASA’s Juno mission with X-ray observations from ESA’s XMM-Newton.