514 msun packed into the size of earth a teaspoon of

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Unformatted text preview: ed into the size of Earth a teaspoon of it weigh as much as a truck! teaspoon of it weigh as much as truck! very EE8086 – Astronomy: Stars, Galaxies & Cosmology Degenerate matter obeys different laws of physics. diff The larger the mass, the smaller it becomes! larger Page 7 EE8086 EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 8 Limit Limit on White Dwarf Mass White Dwarf in Close Binary Chandra formulated the laws of degenerate matter. won Left to itself, a single white dwarf will simply cool off into a black dwarf and never shine as brightly as it once was. Its size will never change. But the situation can be quite different for a white dwarf in a the situation can be quite different for white dwarf in close binary system him the Nobel Prize (Physics) Predicted that gravity will that gravity will overcome electron degeneracy pressure if white dwarf mass pressure if white dwarf mass exceeds 1.4 Msun . energetic electrons hi li hit light speed anything above this mass requires electrons to travel faster than electrons to travel faster than light speed known as the Chandrasekhar Limit as the Limit Subrahmanyan Chandrasekhar Chandrasekhar (1910~1995) EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 9 White Dwarf in Close Binary EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 10 White Dwarf Novae These white dwarfs accretes matter from their mainsequence companions. falling matter forms an whirlpool-look accretion disk friction in disk radiate visible, UV & X-ray light different from protostellar disk differs in size & orbital speed Gravity compresses the H build build-up on the surface . on the surface Both pressure and temperature rise as the layer th builds up with more accreting gas gas. When T> 10m K ignite explosive fusion reaction. a gas shell is blown off Temporarily becomes brighter brighter nova EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 11 EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 12 White Dwarf Nova White White Dwarf Novae minor detonation of H fusion on white dwarf’s surface far less luminous than a supernova as bright as 10,000 Suns for a few days, then fade slowly accretion resumes after explosion & process repeats with period of months to 1,000s years (typically 10,000 years) The nova star system system temporarily appears much appears much brighter. supernova is the total explosion of star (light of 10b Suns!) EE8086 – Astronomy: Stars, Galaxies & Cosmology The explosion explosion drives accreted matter out into space. Page 13 White Dwarf Supernovae EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 14 Supernovae Comparison Accreting white dwarfs can gain mass with time. gain Electron degeneracy cannot support star when accreting white dwarf has mass above Chandrasekhar limit. white dwarf collapses! Collapse raises core temperature runaway C fusion. C undergoes fusion all at once undergoes fusion all at once Supernova Light curve Ultimately leads to explosion of star white dwarf supernova type Ia supernova (type Ia supernova) nothing is left behind Different from those by Fe catastrophe (end of life of highth lif hi mass star). those from Fe catastrophe are typ...
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This document was uploaded on 11/25/2013.

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