red-giant and post-red-giant evolution

red-giant and post red-giant evolution stars

M_initial/M_sun < 0.2 - 0.7 ??	M_initial/M_sun < 5 - 8 M_core/M_sun < 2	M_initial/M_sun > 8 M_core/M_sun > 2
complete electron degeneracy sets in before 3He → C starts: the star is dead	partial electron degeneracy sets in as 3He → C begins	no electron degeneracy (these stars begin life much less dense than the low-mass stars, so that contraction during the main-sequence phase does not cause them to get near electron degeneracy)
P = (P_He) + P_e	P = Kn_e^5/3 + (negligible n_HekT)	P = ( n_He+ n_e)kT
no He Burning	positive feedback: energy released in 3He → C goes into increased reaction rate which leads to explosive He core flash (L ~ L _galaxy) muffled by the envelope... energy released: 1) removes electron degeneracy 2) expands the core (i.e., goes into gravitational energy) 3) produces shock waves that drive envelope away (origin of the planetary nebula)	negative feedback: energy released in 3He → C goes into KE which raises the pressure, thereby expanding and cooling the core... this results in a stable He burning core
no He Burning	3He → C fusion temporarily ceases infall of outer layers reverses explosion of inner core and entire star contracts, thereby re-heating core and layers until 3He → C begins stably in core start-and-stop H → He begins again in shell (bursts of luminosity; thermal pulses) produce shock waves that continue to drive envelope away	3He → C begins peacefully and stably
	eventually core He runs out the C core must contract to maintain thermal pressure (thermal energy continues to flow to surface) before C burning can start, complete electron degeneracy sets in the star is dead it radiates the kinetic energy of the (boson) nuclei, and it dims and cools as the KE is used up	eventually core He runs out C core contracts, heats up, until C burning begins peacefully and stably; the star lives on through another round of fusion each time a fuel runs out, this process continues in the core, until Fe/Ni (endothermic) fusion, which leads to the supernova's implosion

3 stages of planetary nebula development
(around a white dwarf)
[low-mass star death only]
age	phase	examples	central star	nebula
tens or hundreds of years	birth	Stingray, NGC 7027,		jets and disks in process of forming
10³ years	protoplanetary	the Egg (visible) and the Egg (ir) Retina, the Rotten Egg	relatively cool, little uv emission	reflection by dust (torus and concentric rings); no, little gas fluorescence; well-developed jets
few x 10³ years, 10⁴ years	intermediate	Butterfly, Hourglass, Ant, Twin Jet	hotter, significant uv emission	later, faster wind collides with earlier, slower wind or dust concentrated in equatorial plane
few x 10⁴ years	full blown	Cat's Eye, Helix	hottest, most uv emission	completely ionized nebula any asymmetry present due to equatorial dust torus? double star? planetary system?