Thirty million to 50 million years. That's all the time it took to form the star we call the Sun. This may sound like a long time, but let's put it in perspective. Since the last dinosaurs walked the planet, enough time has passed for at least one and possibly two stars like the Sun to have formed, one after the other – utterly from scratch. The details of this miraculous creation are not exceptionally well understood, but astronomers at least have a good grounding in the basics. Perhaps ironically, one star's birth starts at the other end of the line – when other stars die.

Generally speaking, stars make their exit in one of two ways. A low-mass star like the Sun eventually expands its outermost layers until the star becomes a gross, bloated caricature of itself: a red giant. Gradually, the star's envelope expands outwards, all the time becoming thinner, until the dense core of the star is revealed. Such an object is known as a white dwarf. It is a tiny and, at first, white-hot object with a stellar mass – yet confined to live out the rest of its existence within the limits of a planet's radius. The rest of the star meanwhile, the cast-off atmosphere, grows larger and larger. Eventually it becomes nothing but a thin fog of gas spread over more than a light-year. This is the fate that awaits our Sun, as we shall see in detail in Part 4. By contrast, a heavier star dies much more spectacularly. It blows itself to smithereens in a star-shattering explosion called a supernova.