Topic Summaries
Life of a star
Energy and power
Renewable energy and efficiency
Charge, current, and electric fields
Potential difference and resistors
Electricity
Volume and gases
States of matter and heat capacity
Radiation
Nuclear fusion and fission
Forces
Velocity and acceleration
Gravity and Newton's Laws
Moments and elastic potential
Stopping, braking, and momentum
Properties of waves
Electromagnetic waves
Refraction and lenses
Light, colour, and ray diagrams
Absorbing and emitting infrared radiation
Magnetic fields
Motor effect, generator effect, and transformers
Science skills: Experimental procedures
Science skills: Presenting and using data
Science skills: Measuring results
Energy and power
Renewable energy and efficiency
Charge, current, and electric fields
Potential difference and resistors
Electricity
Volume and gases
States of matter and heat capacity
Radiation
Nuclear fusion and fission
Forces
Velocity and acceleration
Gravity and Newton's Laws
Moments and elastic potential
Stopping, braking, and momentum
Properties of waves
Electromagnetic waves
Refraction and lenses
Light, colour, and ray diagrams
Absorbing and emitting infrared radiation
Magnetic fields
Motor effect, generator effect, and transformers
Science skills: Experimental procedures
Science skills: Presenting and using data
Science skills: Measuring results
- All stars start life in the same way a cloud of dust and gas, called a nebula, is pulled together by gravity. Collisions between molecules generate heat to form a ball of gas called a protostar.
- When enough matter is pulled together, the high temperature of the star allows hydrogen to collide through fusion. The energy released from these reactions balances the gravitational forces trying to collapse the star. This is a main-sequence star. When the star runs out of hydrogen to fuse, it starts to collapse under gravitational forces. This allows helium to fuse into heavier elements.
- For low-mass stars (similar size to the Sun): the fusion of helium causes the star to expand into a red giant. When the red giant runs out of helium to fuse, it collapses into a white dwarf. The white dwarf eventually cools into a black dwarf.
- For high-mass stars: helium can fuse into even heavier elements, causing the star to expand into a red supergiant. The heaviest element made in the process is iron.
- When the red supergiant runs out of fuel, it will collapse again. This causes the iron to fuse into even heavier elements, causing energy to be released in an explosion called a supernova. All elements heavier than iron were originally created and released in supernovae.
- Alternatively, the star can collapse into a highly condensed ball of matter called a neutron star, or it can collapse into a microscopic point, forming a black hole.
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