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SESK: Stuff Everyone Should Know · sesk.info/astro-pulsar-lighthouse-model

What are pulsars, according to the lighthouse model?

Spinning neutron stars whose beams sweep past Earth.

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  1. Spinning neutron stars sweeping beams past us ✔
  2. Stars that swell and shrink
  3. Planets reflecting starlight

Why: A pulsar sends out beams of radiation. As it spins, the beam sweeps across space like a lighthouse, and we see a pulse each time it points at us. Swelling stars are pulsating variables, not pulsars.

Huh, didn't know that: The Crab Nebula pulsar, left by the supernova of 1054, pulses 30 times each second.

The dad joke
A pulsar is a neutron star doing pirouettes.
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References

Answer: Spinning neutron stars sweeping beams past us. A pulsar sends out beams of radiation. As it spins, the beam sweeps across space like a lighthouse, and we see a pulse each time it points at us. Swelling stars are pulsating variables, not pulsars.

  1. Astronomy 2e, 23.4 Pulsars and the Discovery of Neutron Stars openstax.org/books/astronomy-2e/pages/23-4-pulsars-and-the-discovery-of-neutron-stars
    astronomers eventually concluded that pulsars must be spinning neutron stars.
    Checked 2026-10-10.

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