August 6th, Lecture 11.docx

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University of Toronto St. George
Astronomy & Astrophysics
Marija Stankovic

August 6 , Lecture 11, AST201H1 Red Giant becomes brighter because it is increasing in size. With a low mass star, carbon core (a layer of helium and on top hydrogen layer). High mass tar have more matter, allow contraction of carbon to continue. Go around electron degeneracy, fusing carbon and produce elements. - p+e  n+ v proton + electron  neutron + neutrino Core made out of just neutrons. In seconds, most of the star’s core is turned into neutrons. Further collapse is prevented by neutron degeneracy pressure. Dense ball of neutrons. The rest of the star is rushing inward at about 20% of the speed of light (0.2 c) and hits an immovable ball of neutrons. The inrushing material rebounds explosively and the star tears itself apart. Supernova! Outshines the light of the whole galaxies. Explosion left, outer layers dissipates. Extremely hot. Pushing material at high speed. Temperatures millions of degrees. Two types of supernova Type II- core collapse Type 1- carbon detonation Looses heat and cool down. White dwarf will become black dwarf. But a white dwarf in a binary system is fed until it bursts. Low mass star in a binary system, end up with a white dwarf. Companion to it. The white dwarf is fed. Limit to build up the mass. 1,44 solar masses. When start building mass onto the white dwarf, spins faster. Once we reach that limit, spin the closer to speed of light. Build more matter, make the electrons move faster than the speed of light, which cannot happen. More matter fall over 1.4 solar masses, huge explosion. Sun will never have a supernova explosion: because it is not a high mass star, not high mass star but no binary star. All atoms heavier than iron come from supernovas. Allowed chemical reactions, fuse elements which are elements than iron into the supernovas. Through these explosions, go back into the environment. Billions years, out of that cloud (enriched) new stars would be formed. Made of the atoms from the core of a dead star. Star- gas-gas shell. Special and General Relativity (in a nutshell) We can only ever measure motion relative to a give frame of reference. Where you are as an observer. All observers will agree with speed of light. Invariant. Velocity of light is still going to be c. And velocity relative to whomever is still c. The invariance of the speed of light has several bizarre consequences. The Twin Paradox. Your twin is earth. You travelling to Vega from 25 light years, 0.999c. Return after 50 years. Come back at 2063. Meet with twin. Twin has aged 60 years. But you have only aged 2 years. Because you are travelling at 0.999c. Gravity  acceleration Gravity  curvature of spacetime Representation of the curvature of the space time. Basically
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