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Hello in his poem Bright Star, John Keats wrote,

Bright Star Wood I was Steadfast as thou art.

For Keats the stars were symbols of eternity,

they were beautiful and ordered and unchanging. Modern astronomy tells a different

story. Stars like everyone else in the universe are subject to change. They're born among

vast swells of gas and dust and they die in the stunning explosions we call supernovae.

They create black holes and neutron stars and in the very beginning of the universe they forge

the elements from which all life is made.

But how do stars keep burning for millions of years? Why do they self-defense? is Paul Murdoch,

for millions of years.

Why do they self-destruct with such ferocity?

And what will happen to the universe when, or is it if, they all go out?

With me to discuss the life cycle of stars is Paul Murdoch, Senior Fellow at the Institute of Astronomy, Cambridge,

Phil Charles, Professor of Astronomy at Southampton University,

and Janne Levin, Advanced Fellow in the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge.

Paul Murdin, how many stars are there in the universe? What are we talking about?

Well, there's one star that's very special to us, the sun, and all stars are suns like that.

In the night sky you can see maybe 5,000 stars, something like that. They look different from the sun because they're so far away, but they're essentially the same.

All of those stars and our sun are members of a collection of stars called the Galaxy, the Milky Way Galaxy, and there are perhaps

30,000 million stars in the Galaxy, and there is a spread of galaxies throughout the whole universe, perhaps as many

...