Supernova 1006, coloured X-ray image. This is the remnant of a supernova whose explosion was seen in 1006AD. It is the brightest in recorded history. 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. Blue areas are X-rays emitted by high energy particles. Red and green areas are very hot gas (around 10 million degrees Celsius). Data from the Advanced CCD Imaging Spectrometer on the Chandra X-ray Observatory.