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 with M < 8Msun ● Red Giant Branch ● Horizontal 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 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 ) 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

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 . If each one “lives” for about 50,000 years, estimate their formation rate (i.e. the number of PNe formed per year).