sequence”) generate energy by hydrogen fusion. They also found stars that
did not ¿ t this correlation. These were stars at the end of their life cycle. We
will discuss them in the next lecture. What the graph shows is that the key
determinant of a star’s life is the size of the initial cloud of matter from which
it is formed. This determines the pressure in its core and the temperature and
speed at which it burns its fuel. This determines how soon it will run through
its fuel and die.
Why are stars so important in the modern creation story? First, they represent
the ¿ rst large, complex objects created by our Universe. Second, stars create
the preconditions for new forms of complexity. They do so in two main ways.
They pump energy out into the cold empty spaces between them, creating
powerful energy À ows. These provide the energy needed to create even more
complex entities (including planets and even ourselves). They also create
new chemical elements needed to form more complex entities (including
ourselves). How they do so is the main subject of the next lecture.
This lecture has described how gravity sculpted stars from the simple raw
materials of the early Universe. But how did the Universe create even
more complex entities such as ourselves? To do that, it had to create more
elements. That was the task of dying stars. Ŷ
Chaisson, Epic of Evolution, chap. 2.
Christian, Maps of Time, chap. 2.
Brown, Big History, chap. 1.
Croswell, The Alchemy of the Heavens.
Delsemme, Our Cosmic Origins, chap. 2.
Essential Reading
Supplementary Reading