Starship Asterisk*

Pulsars are fast-spinning neutron stars that emit narrow, sweeping beams of radio waves. A new study identifies the origin of those radio waves. Credit: NASA/GSFC

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When Jocelyn Bell first observed the emissions of a pulsar in 1967, the rhythmic pulses of radio waves so confounded astronomers that they considered whether the light could be signals sent by an alien civilization.

The stars act like stellar lighthouses, shooting beams of radio waves from their magnetic poles. For more than a half-century, the cause of those beams has confounded scientists. Now a team of researchers suspects that they've finally identified the mechanism responsible. The discovery could aid projects that rely on the timing of pulsar emissions, such as studies of gravitational waves.

The researchers' proposal starts with the pulsar's strong electric fields, which tear electrons from the star's surface and accelerate them to extreme energies. The accelerated electrons eventually begin emitting high-energy gamma rays. These gamma rays, when absorbed by the pulsar's ultra-strong magnetic field, produce a deluge of additional electrons and their antimatter counterparts, positrons.

The newborn charged particles dampen the electric fields, causing them to oscillate. The wobbling electric fields in the presence of the pulsar's powerful magnetic fields then result in electromagnetic waves that escape into space. Using plasma simulations, the researchers found that these electromagnetic waves match radio waves observed from pulsars. ...

• Physical Review Letters 124(24):5101 (19 Jun 2020) DOI: 10.1103/PhysRevLett.124.245101
• arXiv.org > astro-ph > arXiv:2001.02236 > 07 Jan 2020