AST 2002 Lecture Notes - Lecture 13: Supernova Remnant, Nucleon, Sn 1987A
Document Summary
O(cid:271)ser(cid:448)atio(cid:374)s of star (cid:272)lusters sho(cid:449) a star (cid:271)e(cid:272)o(cid:373)es (cid:373)ore red a(cid:374)d (cid:373)ore lu(cid:373)i(cid:374)ous it (cid:271)e(cid:272)o(cid:373)es a giant after using all the hydrogen in a star. The burning stops, meaning no more outward pressure. H in the core is exhausted: contraction of the star. It is not hot enough yet to start he fusion, but hot enough for the h around the he core to start fusion. As the core contracts, h begins fusing to he in a shell around the core. Luminosity increases because the core thermostat is broken- the increasing fusion rate un the shell does not stop the core from contracting. Does not begin right away because it requires higher temp than hydrogen fusion- larger charge leads to great repulsion. Helium core- fusion stars neither shrink nor grow because the core equilibrium is temporarily restored. Models show that a red giant should shrink and become less luminous after helium fusion begins in the core.
