BRAINCAKEWhite Dwarfs, Neutron Stars and Black Holes
When fusion stops, what is left of a star's core is a compact remnant. Which kind depends on the mass of the core.
White dwarf. The core left after a low-mass star sheds its outer layers. It is about the size of Earth but contains around half to one solar mass, so its density is enormous (about 109 kg m−3). No fusion takes place; it shines because it is still very hot, and slowly cools over billions of years. Its small surface area gives it low luminosity, which is why white dwarfs sit at the bottom left of the H-R diagram. Collapse is stopped by the pressure of its tightly packed electrons.
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Key terms in this lesson
- pulsar
- A rapidly rotating neutron star that emits regular beams of radio waves, detected as pulses as the beam sweeps past an observer.
- escape velocity
- The minimum speed an object needs to escape a body's gravitational field completely, without further propulsion.
More in Space
- Estimating Stellar Radius and Temperature
- The Hertzsprung-Russell Diagram
- Formation of a Star
- Life Cycle of a Star
- Trigonometric Parallax
- Standard Candles
- The Doppler Effect and Red Shift
- Hubble's Law
All 18 lessons in Space · All Edexcel A-level Physics topics