PHYSICS 20B Lecture Notes - Lecture 11: Type Ia Supernova, Electron Degeneracy Pressure, White Dwarf
Lecture 11:
Star formation, evolution, and death (Part Two)
● White dwarf
○ A star can become a white dwarf once all the nuclear fusion reactions have
ended
○ This can contrast gravity’s force by using electron degeneracy pressure
● Binary systems
○ If a white dwarf has a companion, it can undergo a process called, mass
transferring, in which the white dwarf “sucks” the mass of the companion
■ A white dwarf depends on the electron degeneracy to counter strike the
gravitational contraction, however, it the white dwarf concurs more mass
(through mass transferring), causing an imbalance in the forces, the white
dwarf can explode (the threshold for the explosion is 1.4 M
● Type 1a supernova
○ During a type 1a supernova, it brightens over a period of 2 week, reaches its
peak, then begins to gradually fade
○ During the peak, it can be about 10 billions times more luminous than the sun
○ All type 1a supernovae have about the same brightness because if the white
dwarf passes the threshold, 1.4, it explodes, so that means all white dwarfs
explode at 1.4M, and thus all explosions are similar
○ One can determine the explosions distant and host galaxy through the light
curves measurements
● History of Supernova observations
○ With the development of telescopes, we have been able to find supernovae in
more distant galaxies, and the number of observed supernovae has exploded
● Main two points
○ The conversion of mass to energy explains large luminosistes and the life of
stars
○ Heavy elements in the Universe were created during the life and death of stars,
through nuclear fusion and supernovae
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Document Summary
A star can become a white dwarf once all the nuclear fusion reactions have ended. This can contrast gravity"s force by using electron degeneracy pressure. If a white dwarf has a companion, it can undergo a process called, mass transferring, in which the white dwarf sucks the mass of the companion. During a type 1a supernova, it brightens over a period of 2 week, reaches its peak, then begins to gradually fade. During the peak, it can be about 10 billions times more luminous than the sun. All type 1a supernovae have about the same brightness because if the white dwarf passes the threshold, 1. 4, it explodes, so that means all white dwarfs explode at 1. 4m, and thus all explosions are similar. One can determine the explosions distant and host galaxy through the light curves measurements. With the development of telescopes, we have been able to find supernovae in more distant galaxies, and the number of observed supernovae has exploded.
