Pulsars

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.