Introduction

Compared to the human life span, everything in the Universe seems stationary and constant. We need to think at another time scale to understand that everything moves in orbits and that stars come and go; a time scale of evolution. A human life span, and in some cases even the existence of the human race as a whole, is too short to actually observe dynamic processes in the Universe.

While we cannot wait to see the evolution of one star, we can study many stars in various stages of their evolution, and thus learn about the whole sequence. Modern observations, in particular in wavelengths outside the visible spectrum and also from observatories in space, have contributed very much to our understanding of stellar evolution, although research in stellar evolution remains very much at the forefront of modern astrophysics.

In this module we will discuss how stars are born, live their life - some live much shorter than others - and how there are different ways in which they end their existence.

The material from which stars are made never disappears. This module will also illustrate how stars are formed from the remains of previous stars and how the Universe can be considered as a giant "recycle factory".

Before continuing this EBook, it is advisable to first read our EBook “Stellar Radiation” to learn about the Electro-Magnetic spectrum, spectroscopy and the Hertzsprung-Russell diagram.