Lecture 22 Stellar Evolution Recall column Star Fleet

Lecture 22 – Stellar Evolution Recall column Star Fleet Academy Tues: Nov 4, 18, 25 Noon Alllen 326 Textbook on reserve at Science Library • – – – Read before class: Star Birth Chapt 18 and 19 Stellar Evolution M ~1 Msun (PN & WD): Chapt 20 massive star death (SNe): Chapt 21 stellar populations Chapt 23 (p. 587) Gamma-ray bursts & black holes Chapt 22 – REVIEW GR model of gravity summary

1. Star Formation – cold, dense dusty Molecular Clouds (MC): Recall column • Horsehead Nebula • Bok Globules summary

2. Star Formation (SF) in Cores in MC - Enhancements Recall column summary Green Bank Telescope, mm wavelengths • • 10 ly long dust filaments (orange) filled with pebbles protostars, in cores, may arise in nurturing environment for planets

2. Star Formation - Enhancements: Recall column • Eagle Nebula (HST) summary

2. Star Formation - Enhancements: Recall column • Eagle Nebula. • Evaporating Gaseous Globules (EGGs) summary

3. SF - Enhancements collapse summary Recall column • P causes dense clouds to gravitationally collapse & form stars. • forces: gravity & external P self-gravity

4. Star Formation proplyds with protostars in centre Recall column Kelvin-Helmoltz contraction. summary

5. Star Formation: Nuclear Fusion Begins – bipolar outflow summary Recall column Late stage proto-star or early stage star: • T Tauri stars. • Herbig Haro Objects – bipolar outflows == jets emanating from protostars.

Star Formation: summary Recall column • Note jet coming out of molecular cloud.

Star Formation: Herbig Haro Jets Recall column • Radius 0. 5 to 15 ly long! Moving at 10 km/s. How many km/hr? summary

6. SF: Young stars The Pleiades summary Recall column • Hot young stars blue, massive • Fusion in core Zero Age MS • Still surrounded by dust reflecting blue light. • group of stars with different masses.

6. SF: Young stars The Bubble Nebula by Bernard Michaud Recall column • Radiation & wind from O star bubble in molecular cloud/ISM • diameter 10 ly • M ✪ > 45 M summary

summary Recall column This radio & FIR image shows: - clouds of heated dust where stars are forming (pink). - cold neutral hydrogen gas (diffuse structure) - the interstellar medium (ISM)

summary Recall column C A B Which image shows gas density enhancements that are about to collapse to form proto-stars? ____ Which image shows the stage of protostar formation? ______ Which image is associated with the T Tauri or bipolar outflow stage? _______ Which image shows the stage where stars have nuclear fusion occuring in their cores? _______ D

SF on H-R Diagram : Hayashi Track Recall column • Large, cool protostar in centre of proplyd nebula in upper right. • r contracts & T increases. Kelvin. Helmholtz Contraction. • Fusion in core on MS. summary

SF on H-R Diagram: summary Recall column MS Brown Dwarfs • Brown dwarf stars • small enough masses • do not initiate nuclear fusion of H • do not reside on the MS

SF on H-R Diagram: summary Recall column ZAMS • T~ 15*10**6 K • Zero Age Main Sequence (ZAMS) at left edge of MS with advent of nuclear fusion. • Stars on MS • Evolve off of MS when H in core is converted to Helium (He).

summary Recall column • Name/describe to your neighbour the 6 main stages of star birth like our sun.

summary Recall column STAR

Stellar Evolution: Star Death Recall column • Recall Stefan-Boltzmann Law • r == stellar radius • T == surface temperature summary

Leaving the MS summary Recall column • H converted to He in core • H burning in shell • He not burning no pressure P to counter gravity

summary Recall column

summary Recall column Travels up the Red Giant Branch (i. e. Subgiant Branch) of the HR diagram. Enriches ISM

summary Recall column

summary Recall column

summary Recall column What will happen? Part way through the evolution of 1 solar mass – see next lecture.