Pi

Its story

It is one of the most studied Be stars in the sky: a blue point spinning at dizzying speeds, surrounded by a disc of gas that appears and fades across the decades. Since the early 20th century astronomers have documented its outbursts, its double-peaked, triple-peaked and almost flat-topped spectral profiles, and an invisible companion — likely a white dwarf — that crosses it every 84 days and triggers an X-ray flare. At 782 light-years away, its light pulses with a story that is never quite the same twice.