Crab nebula (M1). Chandra X-ray image of the Crab nebula, the remnant of a supernova. In the centre of the nebula is the remains of the star's core, which has formed a pulsar (blue dot), or neutron star rotating 30 times a second and emitting regular pulses of radiation. When a large star dies, gas shells explode outwards and collide with interstellar material. The energy of the collision ionises the gas, causing it to glow. The crab nebula lies 6000 light years from Earth in the constellation Taurus. This image shows high energy X-rays (2-7 kiloelectonvolts).