The life of a star depends on a delicate equilibrium between gravity and radiation pressure. Gravity pulls the outer layers of the star inwards, heating up its core and driving nuclear fusion. These nuclear reactions produce an outward pressure, which prevents the star from collapsing. When a star has consumed all its elements to sustain fusion, gravity prevails and its life draws near the end. A massive star will then contract violently and explode, illuminating the Universe and expelling matter into space. This enormous blast, beaming brighter than a galaxy, is known as a supernova. The ejected matter forms a beautiful nebula, remnant of the explosion, while the core evolves into a neutron star or a black hole.