Taking the Crab’s pulse

Sweeping beams of radiation from rapidly spinning stars called pulsars vary in intensity. No one knows why. Simultaneous recordings of the Crab pulsar’s visible light, shown in these images to the right of another star, and its radio emissions may demystify the phenomenon. When read left to right and top to bottom, the images show the pulsar reaching peak brightness toward the end of its 33-millisecond rotation.

A. Golden/N.U.I. Galway

Each image was averaged over 500,000 rotations that were captured by a telescope in the Canary Islands. Andy Shearer of the National University of Ireland in Galway and his colleagues determined, moreover, that brighter-than-normal peaks of light precede exceptionally powerful radio pulses. Whatever triggers the giant radio pulses apparently releases energy throughout the electromagnetic spectrum, the astronomers report in the July 25 Science.


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