Overview
This lecture explains magnetars—special types of neutron stars with extremely strong magnetic fields—and the phenomenon of starquakes, as well as their causes and effects.
Magnetars and Magnetic Fields
- Magnetars are neutron stars with extremely strong magnetic fields.
- Only the fastest spinning neutron stars (rotating close to 1,000 times per second) can become magnetars.
- Rapid rotation causes the magnetic field to become tangled and penetrate the solid surface of the neutron star.
Starquakes: Causes and Effects
- The neutron star's solid surface cracks when stressed by tangled magnetic fields, similar to how sunspots form on the Sun.
- These cracks are called "starquakes" (not "earthquakes" since they occur on stars, not Earth).
- Gravity quickly seals the crack, so starquakes last less than a second.
- During a starquake, hotter material from beneath the surface is briefly exposed, greatly increasing the star's brightness.
- Each starquake can release more energy in less than a second than the Sun emits in 100,000 years.
- Such an event would vaporize anything nearby, but no magnetars are close enough to threaten Earth.
Magnetar Brightness and Danger
- Starquakes cause sudden, extreme bursts of brightness from the magnetar.
- These energy bursts are chaotic and do not follow a predictable pattern, unlike pulsars.
Key Terms & Definitions
- Magnetar — a neutron star with an extremely strong and tangled magnetic field due to rapid rotation.
- Neutron Star — the dense, solid remnant of a massive star that has undergone a supernova.
- Magnetic Field — the area around a magnetic object where magnetic forces are exerted.
- Starquake — a sudden cracking of a neutron star's solid surface caused by tangled magnetic fields, releasing enormous energy.
Action Items / Next Steps
- Prepare for the next lecture topic: Black Holes.