The Endpoints of Stellar Evolution Answer Depends on the Star’S Mass Star Exhausts Its Nuclear Fuel - Can No Longer Provide Pressure to Support Itself

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The endpoints of stellar evolution Answer depends on the star’s mass Star exhausts its nuclear fuel - can no longer provide pressure to support itself. Gravity takes over, it collapses Low mass stars (< 8 Msun or so): End up with ‘white dwarf’ supported by degeneracy pressure. Wide range of structure and composition!!! Answer depends on the star’s mass Star exhausts its nuclear fuel - can no longer provide pressure to support itself. Gravity takes over, it collapses Higher mass stars (8-25 Msun or so): get a ‘neutron star’ supported by neutron degeneracy pressure. Wide variety of observed properties Answer depends on the star’s mass Star exhausts its nuclear fuel - can no longer provide pressure to support itself. Gravity takes over, it collapses Above about 25 Msun: we are left with a ‘black hole’ Black holes are astounding objects because of their simplicity (consider all the complicated physics to set all the macroscopic properties of a star that we have been through) - not unlike macroscopic elementary particles!! According to general relativity, the black hole properties are set by two numbers: mass and spin change of photon energies towards the gravitating mass the opposite when emitted Pound-Rebka experiment used atomic transition of Fe Important physical content for BH studies: general relativity has no intrisic scale instead, all important lengthscales and timescales are set by - and become proportional to the mass. Trick… Examine the energy… Why do we believe that black holes are inevitably created by gravitational collapse? Rather astounding that we go from such complicated initial conditions to such “clean”, simple objects! .

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