Artist's impression of the evolution of a hot high-mass binary star (annotated version)

This artist's impression shows how hot, brilliant and high-mass stars evolve. New work using ESO telescopes has shown that most such stars are in pairs. These stars are up to one million times brighter than the Sun, and evolve about one thousand times more quickly. As the stars evolve they expand slowly. The more massive brighter star expands first, until the outer layers start to strongly feel the gravitational pull of the companion, deforming the star into a teardrop shape. The companion then starts to suck material from the primary star. When the primary has been stripped from its entire hydrogen rich envelope it shrinks. At this point the secondary star is now rotating very fast and has an oblate shape. The hot compact star continues to fuse heavier and heavier elements in its centre until it explodes as a supernova. During the explosion a neutron star is born which probably escapes. The secondary is left behind alone. It swells up and becomes a red supergiant with a radius a few times larger than the