Did this video help you?
Star Formation (CIE IGCSE Physics)
Revision Note
Star formation
Extended tier only
- Stars go through a sequence of evolutionary stages, known as the life cycle of a star
- All stars follow the same initial stages:
nebula → protostar → stable star
Nebula
- Stars form from a giant interstellar cloud of gas and dust called a nebula
Protostar
- The gravitational attraction within a nebula pulls the particles closer together until a hot ball of gas forms, known as a protostar
- As the particles are pulled closer together the density of the protostar increases
- This results in more frequent collisions between the particles which causes the temperature to increase
Stable star
- Once the protostar becomes hot enough, nuclear fusion reactions occur within its core
- The hydrogen in the core of the star is converted into helium
- Every fusion reaction releases heat and light which keeps the core hot
- Once a star initiates fusion, it is known as a stable star
- During this stage, the star is in equilibrium as the forces acting on it are balanced
- Gravitational forces act inwards
- This is an attractive force which pulls the outer layers inwards
- Thermal pressure acts outwards
- This is exerted by the expanding hot gases inside the star as energy is released during fusion
Balanced forces in a stable star
The outwards and inwards forces within a star are in equilibrium. The centre red circle represents the star's core and the orange circle represents the star's outer layers
- Once a stable star is formed, the final stages of its life cycle depend on its mass
- The different life cycles are shown below
Summary of the life cycles of stars
Flow diagram showing the life cycle of a star which is the same size as the Sun (solar mass) and the lifecycle of a star which is much more massive than the Sun
You've read 0 of your 10 free revision notes
Unlock more, it's free!
Did this page help you?