Astonomy 62 Lecture #23 LastLast TimeTime Fragmentation Initial Mass Function (IMF) Pre-Main-Sequence Evolution AccretionAccretion DisksDisks andand OutfowsOutfows Astonomy 62 Lecture #22 Example:Example: Find the disk formation radius for a solar mass protostar that starts out as a GMC core with radius 0.1 pc rotating at 10 m/s near the surface. Herbig-Haro Objects Distance Protostars produce powerful ~500pc jets launched from the center Jet length ~4pc of the accretion disk. v ~ 500 km/s 1000 AU Astonomy 62 Lecture #23 TopicsTopics forfor TodayToday Post-Main-Sequence Evolution for stars with M < 8Msun ● Red Giant Branch ● Horizontal Branch ● Asymptotic Giant Branch ● Planetary Nebulae ReadingReading forfor today:today: 13.113.1 (pp.(pp. 446-452),446-452), 13.213.2 ReadingReading forfor nextnext lecture:lecture: 15.1-15.315.1-15.3 (pp.(pp. 518-537)518-537) Astonomy 62 Lecture #23 StellarStellar StructureStructure EquationsEquations G M d P r dT 1 mH G M r = − 2 =− 1− d r r d r k r 2 d M r 2 or o =4 r d r r dT 3 Lr =− kT d r 4 acT 3 4 r 2 P= mH = ,T , X d Lr 2 = ,T , X =4 r d r = ,T , X Post-MSPost-MS EvolutionEvolution 1-3 core H burning (MS) G M d P r kT = − P= d r 2 r mH Core contracts! (Figure 13.1) Observing Protostars A 5Msun star at point #3 on the HR diagram, shortly after H shell ignition. (Figure 13.7) Post-MSPost-MS EvolutionEvolution 1-3 core H burning, core contraction (MS) G M d P r 3-4 shell H burning, = − 2 isothermal He core d r r increases in mass dT 3 Lr =− d r 4 acT 3 4 r 2 (Figure 13.1) Post-MSPost-MS EvolutionEvolution 1-3 core H burning (MS) 8 (for 5MSun: t=10 yr) 3-4 shell H burning, He core shrinks d P G M r = − (t=105yr) d r r2 4-5 shell H burning, He core collapses (SGB) (t=3.5x105yr) 5-6 shell H burning, convective envelope (RGB) (t=3x105yr) 6-8 He core burning, shell H burning (HB) Triple–αTriple–α ProcessProcess 4 4 8 (Figure 13.1) 2He 2 He 4 Be 8 4 12 4Be 2He 6C Post-MSPost-MS EvolutionEvolution 1-3 core H burning (MS) 8 (for 5MSun: t=10 yr) 3-4 shell H burning, He core grows d P G M r = − (t=105yr) d r r2 4-5 shell H burning, He core collapses (SGB) (t=3.5x105yr) 5-6 shell H burning, convective envelope (RGB) (t=3x105yr) 6-8 He core burning, shell H burning (HB) (t=5x106yr) 8- Η and He shell burning, C-O core contracts (AGB) (Figure 13.1) (t=8x106yr) H-burning shell He core 5 Msun star on the early Asymptotic Giant Branch (AGB) (Figure 13.8) Astonomy 62 Lecture #23 AGB star at 8 kpc 0.49" 1 ly Post–MS evolution of 1Msun star (Figure 13.4)Observing Protostars Post–MS evolution of 5Msun star (Figure 13.5) RAFGL 2688 (Egg Nebula) D ~ 1kpc Protoplanetary nebula powered by a late AGB star. We see polarized starlight reflected by dust. RAFGL 2688 (Egg Nebula) D ~ 1kpc Optical image Composite optical (blue) and IR (red and green) image. More Proto-Planetary Nebulae Gomez's Hamburger HST WFPC2 The Youngest Known Planetary Nebula Stingray Nebula HST WFPC2 Diameter = 1.6'' Distance = 5,500pc so Size = 8,800 AU = 0.04pc “Turned on” in the Red [NII] last 20 years! Green [OIII] Blue Hβ Image Credit: NASA, Matt Bobrowsky The Youngest Known Planetary Nebula Stingray Nebula HST WFPC2 White Dwarf Companion Star Gas/Dust Bubble Image Credit: NASA, Matt Bobrowsky Ring Nebula Age is 6000 – 8000 yr Nebula Mass ~ 0.2 Msun L ~ 50 – 100 Lsun Diameter ~ 0.6 pc Distance ~ 770 pc White Dwarf (1.4 - 1.5 Msun) Typical Spectrum of Planetary Nebula Helix Nebula Age is ~10,000 yr Distance ~ 230 pc Eskimo Nebula Cat Eye Nebula Credit: ESA Astonomy 62 Lecture #23 Problem:Problem: There are roughly 15,000 PNe in our Galaxy. If each one “lives” for about 50,000 years, estimate their formation rate (i.e. the number of PNe formed per year). .