Some useful ideas to understand before studying about the life cycle of stars
1. Gravity
Any two objects that have mass attract each other with a force called gravitational force. Both objects experience equal and opposite forces towards each other. The size of the force depends on the mass of the two objects and the distance between them.
2. What does temperature of a substance represent?
The temperature of s substance is a measure of the average kinetic energy of the particles in the substance. If the average kinetic energy is higher, the temperature will be higher.
3. Thermal Radiation
All objects emit electromagnetic radiation due to their temperature. This radiation is called thermal radiation. The objects emit the full spectrum of electromagnetic radiation. The temperature of the object determines the type of radiation that will have the highest intensity among all types of electromagnetic radiation. The hotter the object the higher the frequency of the type of radiation that will have the highest intensity. For example, for objects at temperatures up to a few hundreds of degree Celsius, the highest intensity of radiation happens to be infrared radiation.
4. Expansion and cooling
In certain cases, when an object expands, it causes the object to cool. The details are beyond the GCSE specification. We will come across an example of this happening in astronomy.