Pulsar

Pulsars are among the most fascinating and precise objects in the universe, formed when massive stars undergo supernova explosions and collapse into incredibly dense neutron star. These cosmic lighthouses have revolutionized our understanding of stellar physics and provided tools for testing fundamental physics theories.

Physical Characteristics

Structure

• Ultra-dense core composed primarily of neutrons
• Typical diameter of only 20-25 kilometers
• Mass ranging from 1.4 to 3 solar mass
• Incredibly strong magnetic field (up to 10¹² gauss)

Rotation

• Periods ranging from milliseconds to seconds
• Extremely stable rotation rates
• Gradual slowdown due to electromagnetic radiation

Emission Mechanism

The characteristic pulsing of these objects occurs due to the misalignment between their rotation axis and magnetic axis. As the pulsar rotates, beams of radiation emanating from its magnetic poles sweep across space like a lighthouse beam. When these beams cross Earth's line of sight, we detect regular pulses of radiation.

Types of Pulsars

1. Radio Pulsars

   • Most commonly observed type
   • Emit primarily in radio wavelengths
   • Used as precise astronomical clocks

2. Millisecond Pulsars

   • Rotation periods under 30 milliseconds
   • Often found in binary star
   • Believed to be "recycled" through accretion

3. Magnetars

   • Extremely powerful magnetic fields
   • Occasional massive energy bursts
   • Rare and typically young

Scientific Applications

Pulsars serve as invaluable tools for:

• Testing general relativity
• Detecting gravitational waves
• Studying interstellar medium
• Creating precise timing standards

Historical Discovery

The first pulsar was discovered by Jocelyn Bell Burnell in 1967, initially designated as LGM-1 ("Little Green Men") due to its remarkably regular signal. This discovery opened a new chapter in astrophysics and earned the 1974 Nobel Prize in Physics (controversially not awarded to Bell Burnell).

Evolution and Fate

Pulsars gradually slow their rotation over millions of years as they lose energy through electromagnetic radiation and particle emission. Eventually, they may become too weak to detect, entering a "graveyard" orbit where they continue to drift through space as silent neutron stars.

Cultural Impact

The regular signals from pulsars have captured public imagination and influenced science fiction. The first known binary pulsar system's plotting was used as a map on the Pioneer plaque, representing humanity's location in space to potential extraterrestrial civilizations.