AST201H5 Lecture Notes - Lecture 11: Double Star, Nuclear Fusion, Compact Star
Document Summary
High mass star adjusts to depleted h: core shrinks and evelope expands and cools -> supergiant star. Very hot, dense core -> many fusion reactions up to iron. Iron cannot be fused and produce energy -> core collapses -> supernova explosion -> recycles its fusion products = all chemical elements heavier than helium. Double stars are born together but age at different rates: more mass star expands -> transfers mass to companion. White dwarfs have huge densities = 10^9 kg/m^3. degenerate pressure, greater mass -> smaller diameter, mass of 1. 4 msun has diameter = 0 km = chandrasekhar limit. Recall chapter 13 double stars the giant star can transfer mass to the small. A white dwarf in a double star can gain fresh matter from its companion"s surface. Nuclear fusion explosion (h->he) occurs on the surface of the white dwarf = observable. White dwarf"s luminosity = 100,000 x lsun. nova explosion - a new star appears in the sky.
