ASTRON 2B03 Lecture Notes - Lecture 10: The Big Questions, White Dwarf, Solar Mass
17 Dec 2015
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Normal star - gravity balanced by pressure from nuclear fusion. White dwarf - gravity balanced from pressure from not being able to pack carbon and oxygen atoms any tighter. Neutron star - gravity balanced by pressure from not being able to pack neutrons together any tighter. Black hole - gravity not balanced, total collapse. Earth as is: 40000 km/hour needed for an object to not return. Earth squeezed to radius of 1 cm: (cid:2)escape velocity(cid:3) greater than speed of light black hole. Squeeze the sun down to a radius of 3 km black. Black holes are objects whose gravity is so intense that light cannot escape them. The event horizon: so, every object has a critical size below which it becomes a black hole. (cid:2)schwarzschild radius(cid:3): the larger the mass of the object, the larger the critical radius. Not a physical surface, but an information barrier.
