What causes the radio pulses of a pulsar?
A) The star vibrates.
B) As the star spins, beams of radio radiation sweep through space. If one of the beams crosses Earth, we observe a pulse.
C) The star undergoes periodic explosions of nuclear fusion that generate radio emission.
D) The star's orbiting companion periodically eclipses the radio waves emitted by the main pulsar.
E) A black hole near the star absorbs energy and re-emits it as radio waves.
B
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