stellar forensic files: what dead stars tell us about living ones dr. kurtis a. williams steward...
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Stellar Forensic Files:
What Dead Stars Tell Us About Living Ones
Dr. Kurtis A. Williams
Steward Observatory
In a galaxy, the life cycles of stars are the major force of change.
We must understand these life cycles to understand our Galaxy.
During its life, a star’s central nuclear heart is hidden from view.
We need to uncover and study this heart.
Like people, stars have life cycles
Stars are born from large clouds of gas
A star’s middle age is similar to an automobile
When stars get old, they get sick and die
This sequence is seen in the “Hertzsprung-Russell Diagram”
Blue Red
Heavy
Light
BIG
Small
When a star dies, its nuclear ashes are left behind
Gravity squeezes this ash into a very hot, compact object.
Photo: Jones, Stern & Forman/SAO Photo: NASA/Bond et al.
Eventually, gravity is stopped by “degeneracy”
Photo: Psycho Therapy Clothing
White dwarfs tell us how much of a star is used as nuclear fuel.
A lack of white dwarfs tells us which stars explode
Star clusters without white dwarfs are still producing supernovae
Image: S. Kohle & T. Credner
When white dwarfs appear we have reached the critical mass
There is a nice relation between the mass of a star and its white dwarf
Unusual elements in a white dwarf atmosphere may signify planets.
Artwork: NASA/G. Bacon
White dwarfs have atmospheres of nearly pure hydrogen or helium
Photos: Theodore Gray
Photo: CRIACC
Gravity is so strong, other elements sink in a matter of weeks.
Photo: Dartmouth Chemistry Dept.
Art
: NS
BR
I
White dwarfs with other elements must replenish them constantly
© Anglo-Australian Observatory
Photo: SOHO
Image: NASA/DIRBE
White dwarfs tell us how matter is recycled and enriched.
We Recycle!
This atmosphere has elements made during the red giant phase
White dwarfs provide forensic evidence on the inner workings and lives of stars.
Many parts of stellar life are hidden from view until a star dies.
White dwarfs are a window into the hearts and lives of stars.
By studying white dwarfs, we learn about stars long gone