The Solar System - 8.1.2 The Life Cycle of A Star (GCSE Physics AQA)

The Life Cycle of A Star

Star Size and Life Cycle

• Stars have a life cycle. All the stars in our Solar System go through a life cycle. There are various stages in a life cycle, including formation, stabilisation and eventual destruction.
• Stars are various sizes. In our Solar System, the stars are all different sizes. Some are the size of the Sun, some are smaller than the Sun, whilst others are bigger than the Sun. When you look at a star, whether it be via a telescope or just using your eyes, the size you see is determined by i) its actual size, and ii) the distance from you.
• The life cycle depends on star size. The life cycle of a star will depend on the size of the star. Small stars, like the Sun, will go through one particular life cycle, whilst larger stars will go through another life cycle.

Steps in the Life Cycles of Stars

Stars the Size of the Sun

The Sun is a relatively small star in our Milky Way. Its life cycle follows a particular path, as shown below:

Stars Bigger than the Sun

Stars bigger than the Sun will follow a different life cycle:

Summary of the Life Cycle

Here is a summary diagram showing the life cycle of stars.

Forming New Elements

In this section we will learn about the many elements which are found in stars. We will learn how they are formed and distributed.

Formation of the Elements

The fusion reactions that occur in stars are used produce new elements. In the core of the star, we find hydrogen nuclei and many other light elements. At very high temperatures, the nuclei of these elements are used in nuclear fusion reactions.

As the nuclei of these light elements join together, they will form new, heavier elements. For example, when hydrogen nuclei join together, they form helium nuclei.

Distributing the Elements

Although elements are formed in the cores of stars, they can be distributed across the universe. This is occurs through a supernova, which we discussed in the previous section. The elements are distributed along with the layers of gas and dust that are flung into space.

Heavier Elements

In the previous section, we discussed that very heavy elements are produced in stars bigger than the Sun. These elements can be heavier than iron. These elements are the ones that will be distributed in supernovae throughout the universe.