Chapter 22/23: Stellar Explosions, Evolution of High Mass Stars, Star Clusters Flashcards
What is a novae (white dwarf)?
Mass transfer happens via Roche lobe overflow in binary stars close to each other. The white dwarf then explodes as a nova.
What is Chandrasekhar’s limit for white dwarfs?
1.4 Solar Masses
What is a Type Ia Supernovae (from white dwarf)
More massive pair, white dwarf completely explodes, leaving nothing behind.
At what temp does the CNO cycle dominate?
temperatures that exceed 20 million K (4 Solar Masses)
What is the CNO cycle?
Hydrogen is converted to Helium via a path that includes carbon (carbon-12 is the catalyst) C + 4 H gives C + He + neutrinos + energy
What makes carbon burn at 600 million K
C-O mass is greater and gravity takes over (collapse is not stopped (over 1.4 solar mass)) every successive element is formed.
What is the onion?
Each layer is making different elements (star near death)
What is special about Iron (Fe)
It is the last element that is produced and its the heaviest (produced in core)
What does Fe do?
It absorbs energy (gamma rays) and breaks up into helium nuclei and neutrons.
What is the formation of a neutron for high mass stars?
As the core gets denser, protons and electrons combine with one another to become neutrons.
What is neutron degeneracy pressure?
Imploding layers rebound off the rigid core in an explosion (bounce the ball on bounce ball)
Type II Supernovae
Is made by a core collapse.
What is Nucleosynthesis?
it occurs as new elements are created in the explosion. (example Crab nebula)
Type Ia vs Type II
1a = white dwarf explodes (no hydrogen spectrum and more luminous). II = massive star collapse (hydrogen spectrum)
What is a Neutron Star?
What is left over after a Type II supernova (if between 1.4 and 2.3 solar masses) the size of Manhattan but very large mass and fast rotation.
