Veil nebula (NGC 6995). This is the eastern part of the veil nebula, the remains of a supernova that is thought to have exploded between 5000 and 8000 years ago. 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 veil nebula is located in the constellation Cygnus, approximately 1,500 light years from Earth.