Manuel Pichardo Marcano

The binary star KL Dra works like a neon clock: every two months it lights up for a few days, and between these outbursts it blinks with short but bright pulses. For eleven straight years, telescopes have kept their eyes on it, and now the whole mechanism is visible.

A red giant in the constellation Cygnus has swelled so much that its outer layers are spilling onto a small but heavy neighbor — a white dwarf. The gas swirls around the dwarf like water down a bathtub drain, falling onto it. But in CH Cygni, this flow is not calm: every 682.5 seconds, the X-ray emission flares and fades.