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A stellar overview
A Very Short Introduction
By Andrew King
122 pp. Oxford University Press
Reviewed by Bob Sanchez
“Every atom of our bodies has been part of a star, and every informed person should know something of how the stars evolved,” writes Andrew King, Professor of Astrophysics at the University of Leicester. Where do stars come from? What are they made of? How long will they live? And how do we know? These are some of the questions King addresses in Stars, the latest volume in a long Oxford series subtitled A Very Short Introduction.
King takes the reader from Auguste Comte's belief in 1835 that because stars were unreachable their chemical composition was unknowable to the prediction that the Universe will end as dead iron bodies and black holes. He does a good job explaining to the lay reader how it will get to that end.
So how do scientists know what no one can physically sample? They have learned what Comte did not know, about the characteristics of light, about quantum physics, atomic structures, and the behavior of the various elements under intense pressure and heat.
Stars is by no means a technical read, but readers should have some understanding of basic science before diving into it. King recommends the book as supplementary reading for an introductory astronomy course, or “astronomy/physics for poets courses in the US.” Well, maybe, but this is not a dumbed-down book for starry-eyed poets who fear science. It's mostly math-free and filled with clear prose:
A large fraction of the naked-eye stars in the night sky are actually red giants, Betelgeuse being the most prominent example.
The red giant phase is not the end of a star's life story. Deep in the core, the density and temperature slowly rise until helium is able to burn, making carbon and oxygen. This heats up the helium core and makes it expand. The processes that made the envelope swell when the core contracted at the end of hydrogen burning now go into reverse: to conserve gravitational and thermal energy, the envelope now shrinks.
Happily for the layperson, this stellar overview doesn't get much more technical than that.
Luckily, a lot happens before galactic remains compress into dreary, lightless lumps. Our Sun is roughly in the middle of its 10-billion-year evolution, and it has enormous amounts of thermal energy that will keep it looking much the way it is for a long time to come. It stands in the middle of the “main sequence” of stars that burn hydrogen in their cores. Eventually, however, it will expand into a red giant, with a size approaching the radius of the Earth's orbit. Then it will collapse into an inert white dwarf as it expends the remnants of its energy.
With Stars, King seeks to inform the intelligent reader, and he achieves his goal well.