AstronomyLesson 3 of 3 in the course The Death of Stars

Pulsars: Discovery, Rotation, Evolution, and Magnetars

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces neutron stars and the research that led to the discovery of pulsars. It shows how careful analysis of radio observations revealed an unexpected kind of astronomical object.

A neutron star can remain after a massive star explodes in a type II supernova. It is extraordinarily compact: a typical neutron star is only about 10 kilometers in radius, yet its mass is greater than 1.4 and less than about 3 times the mass of the Sun. Its density is around 101410^{14} grams per cubic centimeter, and gravity at its surface is about 101110^{11} times stronger than gravity at Earth’s surface.

All flashcards

Why was the first pulsar signal nicknamed “LGM”?
Its precise pulses briefly suggested a possible artificial signal; “LGM” jokingly meant “little green men.”
How often did the first unusual pulsar signal repeat?
It produced a pulse every 1.33728 seconds.
What does “pulsar” mean?
It is shortened from “pulsating radio source.”
What made the Crab pulsar notable across the electromagnetic spectrum?
Its pulses can be detected in radio waves, visible light, and X-rays.
What is a magnetar?
A neutron star with an exceptionally strong magnetic field.

Quiz questions

  1. Why does a rotating stellar core spin faster when it contracts into a neutron star?Answer: Conservation of angular momentum increases its rotation rate as it contracts.
  2. What geometric feature helps a pulsar’s radiation beam sweep across space as it rotates?Answer: Its magnetic axis is tilted relative to its rotation axis.
  3. What supplies the energy that keeps the Crab Nebula glowing?Answer: The Crab pulsar’s rotational energy, carried outward by particles and radiation.
  4. Why can a pulsar remain observable after its supernova remnant is no longer visible?Answer: The remnant’s gas disperses much sooner than the pulsar’s observable lifetime ends.
  5. What can trigger a powerful radiation flare from a magnetar?Answer: Magnetic stresses can crack its rigid crust in a starquake.

Based on Astronomy 2e by Andrew Fraknoi, David Morrison, Sidney Wolff (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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