Mu

Its story

Mu Persei, 51 Persei, is a yellow supergiant about 53 solar radii across, shining with more than 2,000 times the Sun's light at 901 light-years. It does not travel alone: a B9 blue companion orbits it every 284 days along a nearly circular path. The light arriving tonight left the atmosphere of that pair in the twelfth century, before the great Castilian chronicles were written.