Stars do not live forever, and our Sun will one day die, and with it all life on Earth. Five billion years from now, when our planet has been incinerated to a crisp, our local star will have run out of the fuel that powers its nuclear fusion. Its hydrogen depleted and all consumed, it will have metamorphosed from the relatively stable yellow dwarf star that we see today into a bloated angry red giant, its outer layers and atmosphere occupying most of the inner solar system.
Indeed, the Sun is already imperceptibly increasing in temperature – it’s 20 per cent hotter now than when the Earth coalesced out of the Sun’s proto-planetary disk 4½ billion years ago, and within a couple of hundred million years the Earth will become uninhabitable. This chain of events is inevitable and, over different time periods, happens to all stars.
Stars coalesce by gravity out of clouds of interstellar gas, made up largely of the original constit-uent elements of the universe: about 75% hydrogen and 25% helium, plus trace amounts of lithium – the latter two termed ‘metals’ in the unorthodox nomenclature of astronomy.