Neutron Stars & Black Holes (OCR A Level Physics)

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Katie M


Katie M



Neutron Stars & Black Holes

  • In the final evolutionary stages of a massive star's life cycle, the remnant left after a supernova explosion will either be:
    • A neutron star
    • A black hole

Characteristics of a Neutron Star

  • Neutron stars are objects formed in stars with cores which have masses greater than the Chandrasekhar limit
  • Neutron stars are:
    • Extremely dense
    • Very small
  • To put into perspective how dense and small a neutron star is:
    • The density of a neutron star is 4 × 1017 kg m−3
    • The density of the Earth is 5 × 103 kg m−3
    • The density of a white dwarf is 1 × 109 kg m−3
    • A neutron star with the mass of the Sun would be only 30 km in diameter
  • Some neutron stars rotate rapidly (up to 600 times per second) emitting bursts of highly directional electromagnetic radiation
    • These stars are called pulsars


Characteristics of Black Holes

  • The core collapses into an infinitely dense point called a singularity
  • A singularity is defined as:

A theoretical point at which matter is compressed to an infinitely small point and the laws of physics, as they are currently understood, break down

  • The gravitational field is so strong that nothing, not even light, can escape it
    • This region is known as a black hole
  • The boundary at which light and matter cannot escape the gravitation pull of the black hole is called the event horizon
  • The escape velocity beyond the event horizon is greater than the speed of light, hence photons cannot escape from a black hole


Characteristics of a Black Hole

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Katie M

Author: Katie M

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.

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