When Stars Blow Up

What Stars Explode?

•Cataclysmic variables•Novae•Supernovae

Cataclysmic Variables•Binary star systems incorporating a white dwarf

•Outbursts due to disk instabilities

GK Per = Nova Per 1901

NovaeThermonuclear detonations on a white dwarf

•Hydrogen accumulates, mainly from accretion in a CV•At the base of the accreted layer, electrons becomedegenerate•When the temperature reaches a few MK, fusion begins•Degenerate fusion is a runaway.•All the H fuses to He and heavier elements in a sound-crossing time (a few minutes)•The star increases in brightness ~ 10,000 times•Most of the matter is ejected

Supernovae

SupernovaCollapse of a massive stellar core

•Type Ia: core collapse of a 1.4 M white dwarfo complete detonation of the core - no remnant

•Type II: core collapse of a star with M > 8M

o yields a neutron star or black holeo core collapses when fuel all used up and gravity wins

Will the Sun Explode?

No!

•The sun is not a white dwarf•The sun is not in a binary system•The sun is not a high mass star

The Fate ofthe Sun

•Brightens on main sequence•Red Giant•Planetary nebula + WD