Beginnings—Star Birth

Abstract

The life of a star, from birth to death, may take several billion years — in some cases, tens of billions — so how can we say with any certainty that we know how stars evolve? After all, human beings have only been observing the universe for a few thousand years! Well, if you think about it for a while, it isn’t difficult to work out. Take for instance a forest — full of oak trees of all sizes, saplings, young trees, old large trees, dead trees fallen over, and so on. A biologist cannot possibly live long enough to watch a tree grow from an acorn until it falls over and dies! But what he or she can do is to study each aspect of the tree’s growth, from an acorn via a sapling to a full grown tree, and then put these all together to get a fair idea of how it develops and grows. An astronomer can take a similar approach. By observing different stars at different times in their evolution (and there is a rather lot of them to choose from), we can get a fair picture of how a star is born, lives, and dies.