The Life of a Star

The story begins with the simplest stuff in the universe: hydrogen. Huge amounts of hydrogen combined with space dust from old, dead stars from a giant cloud of billions of kilometres wide. This giant cloud is called a nebula and is like a birth chamber for new baby stars. The birth of stars always happens the same way. Gravity pulls the particles in the nebula closer and closer to each other. At a certain moment, a chunk is created that grows larger and larger. The gravity of this chunk also grows larger and larger, and the particles in the middle of the chunk become more and more compressed. The chunk heats up and slowly changes into a baby star. How the rest of the stars' life goes, depends on its size.

If the baby star isn't large enough, nothing happens. The chunk will cool down. This is called a brown dwarf.

If the baby star is large enough, the temperature rises to up to 10 million °C and nuclear reactions will start. During these reactions, hydrogen (H) is converted into helium (He) , creating huge amounts of heat and light. If this happens, a new star is born!

There are three possible ways of life a star can have. Which one depends on the size of the star.

Small stars

Stars smaller or a little larger than our Sun.

1. This star has enough hydrogen to burn for around 10 billion years, of which 5 billion years have already passed.
2. The amount of heat and light a star emits depends on the amount of weight it loses when converting hydrogen to helium our Sun loses 4 million tons per second.
3. When the 10 billion years are almost over, the star runs out of hydrogen and a lot of things will happen. The inner part of the star shrinks and heats up, while the outer part grows and cools down. The star will then appear red and large. This is called a red giant. When the sun grows this large, the earth will incinerate.
4. A red giant doesn't have much longer to live. Sometimes it explodes and is called a nova. It is also possible that it slowly changes into a hot core, surrounded by gasses. This is called a planetary nebula. (This has nothing to do with planets)
5. After a while, all that is left of the nebula is the core. This is called a white dwarf. White dwarves are very small, but also very heavy. A cup full of white dwarf would weigh over 10 tons!
6. Eventually the white dwarf will cool down and become a black dwarf, but no one knows if the universe is so old that there are already black dwarves. They're also too small, too far away and too weak to be seen.

Big stars

Stars that are heavier than 1.4 times our sun.

1. This star burns its hydrogen much faster. They are out of hydrogen after only a few million years. At the end of its life, it is called a red super giant.
2. When the star is out of fuel, everything suddenly stops and the star implodes. What is left, weighs at least 10 billion tons per cup! The temperature also raises to up to 100 billion degrees Celsius. The star will then explode. This is called a super nova. When this happens, huge amounts of energy are released.
3. What remains after the blow, is about 20 kilometres in diameter and is called a neutron star. The gravity of this neutron star is huge! A neutron star rotates around its axis and emits radiation, that's why it is also called a pulsar. Eventually, the pulsar will stop rotating and die.

Huge stars

Stars that are at least 3 times heavier than our sun.

1. The star burns all its hydrogen, explodes and is then called a super nova.
2. It will then implode. The star presses itself together so strongly, that even the smallest particles it exists of will break down. The time stops running and what remains, is the strangest thing in the universe. It's only a few kilometres wide, but weighs more than a pulsar. It's a black hole.