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ASTRON 2B03 (132)
Lecture

Oct.26 - 2B03.docx

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Department
Astronomy
Course Code
ASTRON 2B03
Professor
Laura Parker

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Oct. 26 – 2B03 26/10/2011 9:29:00 AM Low mass stars – fusion stops when a carbon core is formed.  End product is a white dwarf High-mass stars – can fuse elements up to iron.  End product: neutron star or black hole Pressure (coming from nuclear reactions) outwards, stabilizing with equal amount of gravity coming in.  If pressure outweighs gravity, star gets bigger. If gravity outweighs, it contracts. Massive star -> supernova -> supernova remnant. All heavy elements came from supernovae (gold, lead). If you squeezed earth into a tiny volume (1cm) -> the escape velocity would be greater than the speed of light and would result in a black hole. All the different escape velocities -> none close to the speed of light. Event Horizon  Every object has a critical value under which it becomes a black hole -> The Schwarzschild Radius  We call it a surface – but its more like a barrier. o Nothing within the S radius can ever come out.  Singularity – a point of infinite density. Anything that falls in doesn’t come back in. Gravitational force changes as you go inside a spherical object. Black holes have alot of mass in a ridiculously small volume. Higher density, larger the surface gravitational force. If you are magically inside the event horizon (can’t really -> be ripped apart), and you had a laser, light would not escape. Black hole – singularity, point at which density is infinite.  Event horizon -> space around which light cannot escape. Black holes don't suck.  If you turn sun into a black hole, we wont be sucked or anything. Gravity would remain the same. Neutron star – pretty dense, 1/3 of the speed of c. High density -> higher escape velocity . Black
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