What are stars made of?

eagle nebula

What are stars made of? How big is the universe? How big are we? How do stars live and die and become funny little us?

Who couldn’t love the stars that glimmer above our heads on fine nights?

Astronomers estimate there are about 100 thousand million stars in our galaxy. Our own sun – and we’ve seen plenty of movies to consider its fiery vastness – is pretty medium-sized, as stars go. And it’s only one of 100 thousand million. It’s the middle child. Yes; to us, that star is one of the most beautiful, fearsome and nurturing things we’ll ever know. Now times that splendour by 100 thousand million. There isn’t a name for that type of hugeness of substance and spirit. It’s ineffable.

Our galaxy is part of the Andromeda cluster, which consists of many galaxies, which contain around 100 thousand million stars each. This cluster is believed to be part of a larger cluster of clusters that is believed to be a part of an even larger cluster of clusters – which contain clusters. Are you getting vertigo yet? Are you beginning to feel in your very bones the inadequacy of the word ‘big’?

How big are stars? How big is the universe?

Let’s have a taste of big and have a look at a romantic vision of earth’s place in the universe in comparison to those clusters of star clusters. If we can imagine big, we can appreciate the beauty of the stars, and we may even be able to appreciate the science behind them.

The life cycle of a star

  1. Stars are formed in a Nebula, which is basically a large cloud of dust and gas. Gravity makes the dust and gas spiral together and form a proto-star.
  2. As gravity compresses the proto-star, the temperature rises until nuclear fusion is possible.
  3. Nuclear fusion is when Hydrogen atoms are able to combine to create helium atoms. This releases a large amounts of light and heat energy and creates a chain reaction. The energy also forces surrounding particles outward which then might spiral together to create planets. And, eventually, us. In the same way that, give or take a mind-expandingly long amount of time, our planet will be destroyed and the resulting particles may form a Nebula, then a proto-star. “By the sweat of your face you shall eat bread until you return to the ground, for out of it you were taken; you are dust, and to dust you shall return.” The outward energy created by the fusion helps the sun keep its shape as it counteracts the gravitational force pulling everything inward. The star is now called a main sequence star.
  4. The star is now in a long stable period, and can stay like that for several billions of years. That is what our sun is currently doing. Oh, how we love our sun.
  5. When a star runs out of hydrogen to convert into helium it begins to die. The outer layers swell up and cool down. When a star is in this stage it is called a red giant. Stars take a long time to die. We are small, but space is very, very big. Revel in it.
  6. A small star will then contract into a white dwarf and then fade away into a black dwarf .
  7. It’s not all doom and gloom for a dying star. Big stars that have swollen up into red giants will undergo more nuclear fusion and contract and expand many times forming heavier larger elements until… BOOM! The star explodes into a supernova, the largest, most violent explosion in the known universe. Doctor Who has probably seen it and lived to tell the tale. Lucky man; no-one else ever will.
  8. The supernova will throw the outer layers of dust and gas out, and will leave an extremely dense core which usually will become a neutron star, or a black hole if it’s large enough.
  9. The dust and gas will then form a nebula and the whole cycle will begin again.

Just think about it. We are all made out of a dying star. You can’t help but feel in awe of these wonderful objects that appear only as faint glitter scattered across the night sky.

Main image: Eagle Nebula, NASA