1	Astro 1050 Wed. Oct. 22, 2003 Today: Finish Chapter 9, Stellar Structure HW discussion Review with time remaining
2	Mass-Luminosity relationship L µ M^3.5Why? Higher mass means higher internal pressure Higher pressure goes with higher temperature Higher temperature means heat leaks out faster Star shrinks until T inside is high enough for fusion rate (which is very sensitive to temperature) to balance heat leak rate
3	Lifetime on Main Sequence L µ M^3.5T µ fuel / L = M/M^{3.5 =} M^-2.5 Example: M=2 M_Sun L = 11.3 L_SunT =1/5.7 T_Sun
4	How about a 0.5 solar mass star? M = 0.5 M_sun Time = Luminosity =
5	How about a 0.5 solar mass star? M = 0.5 M_sun Time = 5.7 times solar lifetime Luminosity = 0.09 solar luminosity
6	Width of Main Sequence – and Stellar Aging As star converts H to He you have more massive nuclei Pressure related to number of nuclei Gravity related to mass of nuclei Pressure would tend to drop unless something else happens Temperature must rise (slightly) to compensate Luminosity must rise (slightly) as heat leaks out faster
7	Orion Nebula: A Star-Forming Region Red light = Hydrogen emission Blue light = reflection nebula Dark lanes = dust Astronomy Picture of the Day: http://antwrp.gsfc.nasa.gov/apod
8	Protoplanetary Disks in the Orion Nebula Dusty disk seen in silhouette Central star visible at long wavelengths
9	Herbig-Haro objects: The angular momentum problem As clouds try to collapse angular momentum makes them spin faster A disk forms around the protostar Material is ejected along the rotation axis
10	Herbig-Haro 34 in Orion Jet along the axis visible as red Lobes at each end where jets run into surrounding gas clouds
11	Motion of Herbig-Haro 34 in Orion Can actually see the knots in the jet move with time In time jets, UV photons, supernova, will disrupt the stellar nursery
12	Homework #6 Won’t go through solutions here, but we can visit WebCT for specific problems and discuss their solution. Particularly issues so far seem to involve spectroscopic parallax and density.
13	For Exam #2: “Essay Questions” (2) will involve at least some of the topics below: Temperature of Stars Binary Stars HR Diagram Ages/Lifetimes of Stars Stellar Fusion
14	Review Chapters 5-9 Chapter 5: Astronomical Tools Electromagnetic Spectrum Optical Telescopes Resolving Power of Telescopes Space Astronomy (No Questions about Pink Floyd or the Dark Side of the Moon!)
15	Review Chapters 5-9 Chapter 6: Starlight and Atoms Model Atom, Energy Levels Absorption Lines Blackbody Spectrum Wien’s Law Steffan-Boltzmann Law Temperature of Stars Wien’s Law, the Balmer “Thermometer” Stellar Classification (OBAFGKM) Doppler Effect
16	Review Chapters 5-9 Chapter 7: The Sun Atmospheric Structure Sunspots/Magnetic Phenomena Nuclear Fusion – proton-proton chain Solar Neutrino “Problem”
17	Review Chapters 5-9 Chapter 8: The Properties of Stars Distances to Stars Parallax and Parsecs Spectroscopic Parallax Intrinsic Brightness: Luminosity Absolute Magnitude Luminosity, Radius, and Temperature Hertzsprung-Russell (H-R) Diagram Luminosity Classes (e.g., Main Sequence, giant) Masses of Stars Binary Stars and Kepler’s Law Mass-Luminosity Relationship
18	Review Chapters 5-9 Ch. 9: The Formation & Structure of Stars Interstellar Medium Types of Nebulae (emission, reflection, dark) Interstellar Reddening from dust Star formation Protostar Evolution on H-R Diagram Fusion (CNO cycle, etc.) Pressure-Temperature “Thermostat” Stellar Structure (hydrostatic equilibrium, etc.) Convection, radiation, and opacity Stellar Lifetimes