Pi

Its story

Pi Herculis marks the northeastern corner of the Keystone, the bright quadrilateral every observer recognizes as the heart of Hercules. Beneath its orange hue hides a luminous giant: about 64 times the Sun's radius and over a thousand times its light, seen from 367 light-years away. A slow six-hundred-day pulse betrays the deep breathing of a star that has already exhausted the hydrogen in its core.