M9 Neutron Stars and Pulsars

Topic

The central figure of this model is the neutron star, envisioned as a giant, rotating magnet.

Neutron stars—remnants of the core collapse of the most massive stars—attain nuclear densities where matter consists almost entirely of neutrons. The equation of state for matter at such extreme densities remains uncertain; measuring the maximum observed mass among actual neutron stars offers the most direct observational test currently available to constrain that equation of state.

Pulsars are rapidly rotating neutron stars with intense magnetic fields that emit periodic beams of radio radiation, and sometimes X-rays or gamma rays as well. Classifying a pulsar based on its rotation period and the slow rate at which that period increases allows the entire pulsar population to be categorized by age and magnetic field strength; this includes millisecond pulsars, which have been "recycled" through the past accretion of matter from a companion star.

The rotational energy stored in the pulsar is gradually depleted by the magnetic radiation it emits, causing its spin to slow down over time; the Crab Nebula, for instance, continues to shine, powered precisely by the ongoing spin-down of the pulsar at its core. Thus, from the neutron star that opens this document to the nebula—powered by the pulsar’s spin-down—that concludes it, and taking in the uncertain equation of state of their matter and the classification of pulsars by period, neutron stars and pulsars ensure that a single rotation, born from the collapse of a massive star, ends up illuminating for millennia the nebula left in the wake of that very explosion.

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