GK Persei nova. Composite image of the classical nova GK Persei, which lies around 1500 light years from Earth. Classical novas are outbursts produced by a thermonuclear explosion on the surface of a white dwarf star, the dense remnant of a Sun-like star. Image composed of X-ray data from the Chandra X-ray Observatory (blue), optical data from the Hubble Space Telescope (yellow), and radio data from the Very Large Array (pink). The X-ray data shows hot gas, whilst the radio data shows emission from electrons that have been accelerated to high energies by the nova shock wave. The optical data reveals clumps of material that were ejected in the explosion.