Stellar Evolution

Stellar Evolution – The Life and Death of Stars

A Planetary NebulaThe planetary nebula M2-9 (© Hubble Space Telescope.) Everything on Earth, with the exception of hydrogen and helium, was made in stars. The hydrogen and most of the helium in the universe were made when the universe was only a few minutes old. We and our Earth are star dust or, if you prefer, the nuclear waste of 8000 million years of stellar evolution.

This is the story of the birth and death of stars, of the origin of the elements and of the fight of matter against gravity, a fight which gravity always wins. It is a story based on many years work starting in 1814, when J. Fraunhofer first saw dark lines in the spectrum of the Sun. By the mid-19th century, it was understood that these lines revealed the presence of many elements in the Sun that are also found on Earth.

Early in the 20th century, the development of quantum theory allowed us to use measurements of the strength of dark lines to find the composition and temperature of the Sun and other stars. Our understanding of how and where all the elements in the universe were made came in 1957, from a paper written by G. R. and E. M. Burbidge, W. A. Fowler and Fred Hoyle.

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