The Sun as a Star
Physics: Cambridge International GCSE Supplement, topic 6.2.1
The Sun
The Sun was formed from a cloud of dust and gas (called a nebula). The forces of gravity pulled the dust and gas together.
Cloud of gas and dust
- The gas and dust collapsed.
- The cloud suddenly decreased in volume as the pressure in the cloud increased.
- This formed a protostar.
Main sequence
- Materials continued to collide (come together) until the temperature and pressure were high enough for hydrogen nuclei to start fusing and form helium (in nuclear fusion).
- The star then went into a stable period, called a ‘main star sequence’.
Nuclear fusion
- The energy released from the nuclear fusion in the Sun keeps the Sun’s core hot.
Stable
- The Sun is still in its stable main sequence phase.
- In this phase, the outward force of the energy released by nuclear fusion is balanced by the force of gravity pulling the Sun inwards.
Test yourself on The Sun as a Star
Which of these are true of the Sun?
In the Sun, what process creates a force outwards, balancing the inward force of gravity?
Formation of the Sun