CE

Pulsars and Neutron Stars

  • Discovery of Pulsars

    • Discovered by Jocelyn Bell in 1967.
    • Detection of regular pulses of radio waves at intervals of 1.34 seconds.
    • Initial assumptions linked these signals to extraterrestrial life due to their regularity.

  • Understanding Pulsars

    • Currently, there are about 1,500 known pulsars.
    • Pulsar signals vary in shape and period (milliseconds to seconds), akin to stable clocks.
    • The pulsar model was developed by Hewish, who was Bell’s graduate adviser.

  • Mechanics of Pulsars

    • Pulsars are neutron stars that emit beams of radiation.
    • They have two hot spots at the poles that emit radiation due to charged particles accelerated by their spinning magnetic field.
    • The emission of radiation is steady, so when Earth is in line with the beam, we detect it.

  • Analogy

    • The radiation emission is likened to a lighthouse: it shines (radiation detected) and then it's out (not detected).
    • Pulsars can be dangerous if too close; radiation could harm living beings.

  • Origins and Types of Pulsars

    • Some pulsars originate from supernova explosions.
    • The pulsar's signal can help trace the speed and direction of the supernova's debris.
    • Pulsars can emit different types of waves (X-ray, visible, radio, gamma), not just radio waves.

  • Physical Properties

    • Neutron stars are incredibly dense: a teaspoon weighs as much as Mount Everest.
    • A typical neutron star is about 15 miles across but contains more matter than the Sun.
    • They spin between 7,000 and 40,000 times per minute and possess strong magnetic fields.

  • Behavior and Lifecycle

    • They emit powerful beams of electromagnetic radiation (including gamma rays) due to their rapid spin and intense magnetic fields.
    • Pulsars appear to blink on and off to distant observers as the beams sweep past.
    • Pulsars slow down over time but some can spin hundreds of times per second due to accretion from companion stars, leading to weaker magnetic fields.

  • Neutron Stars vs. Pulsars

    • While all pulsars are neutron stars, not all neutron stars are pulsars.
    • There could be hundreds of thousands of neutron stars that remain undetected in our galaxy.
    • Detection issues may arise from insufficient radiation or cessation of emission.

  • Stellar Evolution Theory

    • The theory of stellar evolution aligns with pulsar observations after a supernova explosion.
    • This theory explains the formation of neutron stars and their resulting radiation patterns.

  • Conclusion

    • The study of pulsars provides insight into both the lives of stars and fundamental astrophysical principles.