Life Cycle of Stars

Omega / Swan Nebula (M17) Stars are born from great clouds of gas and dust called Stars are born from great clouds of gas and dust called Nebulae

Proto Stars The dust and gas comes together under its own gravity. As they do they heat up, and nuclear reactions start, forming a proto star.

Main Sequence Stage An outward ‘radiation pressure’ is created. When this balances the gravitation attraction then the star stops contracting and the star becomes stable. The star will remain like this for majority of its life. Our Sun is in this stage and which will last 10,000,000,000 years. As the proto star continues to contract the nuclear reactions increase.

During the main sequence Hydrogen is fused together to form Helium in the core. This releases a huge amount of energy. When the Hydrogen runs out in the core there will no longer be an outward radiation pressure and the core contracts again under its own gravity. Nuclear Fusion - The Source of a Star’s Power -

Red Giant The increase in temperature allows Helium to be fused together forming heavier elements up to Iron and Nickel around the core. The outer layers of the star expand forming a red giant. This is Betelgeuse. Its Diameter is the same as the ORBIT of Jupiter

White Dwarf The Cat Nebula The outer layers of the star are shed revealing the hot core. The core illuminates the layers of gas which is called a planetary nebula. The white dwarf will cool to form a red dwarf, a brown dwarf and eventually give out no light as a black dwarf.

Supernova When really massive Red Giants collapse their core is unstable and it explodes as a Supernova. It is during this intense heat and pressure that the heaviest elements are formed though fusion. These are the elements that will make new planets and stars.

During a supernova the core of the star is under immense pressure, such that the electrons of atoms are forced into the nucleus. The protons join with the electrons to form neutrons. Each atom is 100,000 times smaller for the same mass and so incredibly dense. This creates a large ‘gravity well’.

After a Supernova This remnant of the supernova is called a neutron star. If the neutron star is massive enough then not even light can escape its gravity and it is known as a black hole.

The First Stars The first stars in the universe were massive ‘fast burners’ which only contained Hydrogen, because there was only Hydrogen in the Universe. All the other element have been formed in the heart of those and subsequent Stars. Our star, the Sun contains trace elements of iron, oxygen, carbon and magnesium. This tells us that our sun and solar system is much younger than the universe. The first stars in the universe were massive ‘fast burners’ which only contained Hydrogen, because there was only Hydrogen in the Universe. All the other element have been formed in the heart of those and subsequent Stars. Our star, the Sun contains trace elements of iron, oxygen, carbon and magnesium. This tells us that our sun and solar system is much younger than the universe.