Charles Hakes Fort Lewis College1

Charles Hakes Fort Lewis College2

Charles Hakes Fort Lewis College3 Chapter 12 Stellar Evolution/ Supernovae

Charles Hakes Fort Lewis College4 Outline Test 3 Wednesday Death of Low-mass Stars Death of High-mass Stars

Charles Hakes Fort Lewis College5 Current Events yer_embedded&v=vtEvuz_oQ5o yer_embedded&v=vtEvuz_oQ5o reen-brown-dwarf-star-spotted html reen-brown-dwarf-star-spotted html space-spirals.html space-spirals.html

Charles Hakes Fort Lewis College6 Figure White Dwarf on H–R Diagram 12 - For 1 solar mass stars, that is all that will fuse. (need 600 million K for the next reactions to occur.) The outer shell gets “blown off” by the hot, dense, core. Result is a planetary nebula around a white dwarf (13).

Charles Hakes Fort Lewis College7 Figure 12.9 Planetary Nebulae

Charles Hakes Fort Lewis College8 Figure Distant White Dwarfs - globular cluster M4

Charles Hakes Fort Lewis College9 Figure Sirius Binary System - nearby example of a white dwarf

Charles Hakes Fort Lewis College10 Figure Close Binary System

Charles Hakes Fort Lewis College11 Figure 12.13ab Nova A nova forms when the temperature in the accretion disk reaches 10 7 K (H fusion). Such a star might “go nova” dozens (if not hundreds) of times.

Charles Hakes Fort Lewis College12 Figure 12.13c Nova

Charles Hakes Fort Lewis College13 Figure Nova Matter Ejection

Charles Hakes Fort Lewis College14 High Mass Stars

Charles Hakes Fort Lewis College15 Figure High-Mass Evolutionary Tracks Intermediate mass (~4 M sun ) stars fuse carbon, but end up as white dwarfs. High mass (>10 M sun ) stars evolve rapidly. Helium (and other) fusion begins before the star ever gets to the Red Supergiant stage.

Charles Hakes Fort Lewis College16 Figure High-Mass Evolutionary Tracks Wolf Rayet stars (are really big ones) have very strong winds. kipedia/commons/4/49/Crescen thunter.jpghttp://upload.wikimedia.org/wi kipedia/commons/4/49/Crescen thunter.jpg

Charles Hakes Fort Lewis College17 When fusion is happening in the core of a star, the core is A) heating and shrinking B) heating and expanding C) cooling and expanding D) in equilibrium

Charles Hakes Fort Lewis College18 When fusion is happening in the core of a star, the core is A) heating and shrinking B) heating and expanding C) cooling and expanding D) in equilibrium

Charles Hakes Fort Lewis College19 When fusion stops in the core of a star, the core is A) heating and shrinking B) heating and expanding C) cooling and expanding D) in equilibrium

Charles Hakes Fort Lewis College20 When fusion stops in the core of a star, the core is A) heating and shrinking B) heating and expanding C) cooling and expanding D) in equilibrium

Charles Hakes Fort Lewis College21 Figure Heavy Element Fusion Each stage is faster than the stage before. H - 10 million years He - 1 million years C years O - 1 year Si - 1 week

Charles Hakes Fort Lewis College22 Figure Heavy Element Fusion Fusion of iron does not produce energy!

Charles Hakes Fort Lewis College23 Core-Collapse The iron core shrinks and heats. Photons are energetic enough to photo- dissociate iron nuclei. Iron converted back to protons and neutrons. This uses up energy - reduces pressure Collapse accelerates!

Charles Hakes Fort Lewis College24 Core-Collapse Protons and electrons combine to form neutrons releasing neutrinos. Collapse continues until neutrons are in contact with each other. Core “rebounds” and a shock wave throws off the outer layers of the star (mostly H and He.)

Charles Hakes Fort Lewis College25 Core-Collapse Protons and electrons combine to form neutrons releasing neutrinos. Collapse continues until neutrons are in contact with each other. Core “rebounds” and a shock wave throws off the outer layers of the star (mostly H and He.) This collapse takes about 1 second!

Charles Hakes Fort Lewis College26 Figure Supernova 1987A

Charles Hakes Fort Lewis College27 Recent Supernovae

Charles Hakes Fort Lewis College28 Recent Supernovae

Charles Hakes Fort Lewis College29 Figure Supernova Light Curves

Charles Hakes Fort Lewis College30 Figure Two Types of Supernova

Charles Hakes Fort Lewis College31 Carbon Detonation (Type I) Supernova Recall the accretion around a white dwarf star. When the star reaches 1.4 M sun, the density and temperature allow carbon to finally fuse. It fuses everywhere simultaneously. Almost no hydrogen observed in the spectrum of Type I supernova.

Charles Hakes Fort Lewis College32 Figure Supernova Remnants

Charles Hakes Fort Lewis College33 Formation of Heavy Elements Elements heavier than iron require energy input for creation. Supernovae provide the energy source. The expanding cloud contains primarily H and He, but is enriched in heavy elements. The Sun was created from “enriched” interstellar gas and dust.

Charles Hakes Fort Lewis College34 More Precisely 12-1 The Cycle of Stellar Evolution

Charles Hakes Fort Lewis College35 Three Minute Paper Write 1-3 sentences. What was the most important thing you learned today? What questions do you still have about today’s topics?