Second+Test+Subjects+120

List of subjects that will be on the second term test:

 * See Chapters 8 (The Sun), 9 (Characterizing Stars), 10 (The Lives of Stars) & 11 (The Deaths & Remnants of Stars) for more information and details. **

__The Sun__:
 * Three atmospheric layers of the Sun, and their characteristic features (on a very basic level...we moved through this stuff very quickly).
 * Thermonuclear fusion, the energy production caused by thermonuclear fusion and how that energy escapes the Sun.

__Characterizing Stars__:
 * Distance to stars: Stellar parallax, spectroscopic parallax
 * Apparent vs. Absolute magnitude
 * Color of stars (what we see vs. what the star emits at it's "wavelength max.")
 * Color vs. temperature (a revisitation of Wien's Law)
 * Spectral Classification (O B A F G K M)
 * HR Diagram (spectral class vs. luminosity class). Know the diagram and how to label the axes.
 * Star System (binary) and mass determinations
 * Mass-Luminosity relationship

__Interstellar Medium__:
 * Emission nebula (pretty colors...why these colors are there, and which element these colors are representative of)
 * Reflection nebula
 * Interstellar reddening
 * Interstellar extinction
 * Atomic nebula and the 21 cm line!
 * Dark/molecular nebula. Those cold, dark places within which stars form.

__Star Formation__:
 * Star formation triggers: supernovae shockwaves, collisions of ISM clouds and the starlight of nearby O & B type stars (See figure 10-15, p. 278 for an excellent explanation of this last trigger method)
 * Formation of Bok Globules
 * The effects of spin on the forming star(s) of these Bok globules (p. 272)
 * Gravitational collapse leads to increased pressure in the core, which drives the core temperature up.
 * 10 000 000 K needed to ignite thermonuclear fusion. "A star is born!"
 * hydrostatic equilibrium and ZAMS
 * Stellar populations and statistics...more little mass ones formed than very massive ones formed.
 * Lower limit = 8% solar mass, upper limit ~ 100 - 200 solar masses

__Stellar Evolution & Death__:
 * __Low Mass Stars (0.08 - 0.4 solar masses)__:
 * Long time to form, extremely long time on the MS, since they fuse H *VERY* slowly!
 * Fully convective stars. All H to the core, and all H eventually fused.
 * Final product = He ball, that cools and fades over time.
 * NONE of these stars have yet evolved off the MS.
 * __Medium Mass Stars (0.4 - 2 solar masses)__:
 * These stars have "chemically separate cores and shells."
 * When core hydrogen is used up, there is no outward radiation pressure to counteract the gravitation collapse, so the star collapses.
 * This increases the pressure throughout the star, and the temperature throughout the star increases.
 * H fusion begins in a shell surrounding the core and the star's outer regions expand due to this increase in temperature.
 * The star becomes a red giant (up and to the right of the MS on the HR diagram)
 * Meanwhile... in the core, due to electron degeneracy, the core cannot expand and cool, so the core superheats until the helium ignites explosively, in a "helium flash."
 * This red giant phase lasts about 10% the time that the star lasted on the MS
 * Once the He is used up in the core (fused to Carbon via the triple alpha process), the core collapses, and as there **isn't** enough mass to provide the pressure to drive the temperature up to what is needed for carbon fusion, the core collapses.
 * This collapsed core is a "white dwarf" ("white" hot) that ionizes the surrounding layers, which expand as a planetary nebula.
 * A cooling white dwarf will eventually crystallize to a diamond.
 * __High Mass Stars (2 - 8 solar masses)__:
 * These stars have "chemically separate cores and shells."
 * When core hydrogen is used up, there is no outward radiation pressure to counteract the gravitation collapse, so the star collapses.
 * This increases the pressure throughout the star, and the temperature throughout the star increases.
 * H fusion begins in a shell surrounding the core and the star's outer regions expand due to this increase in temperature.
 * The star becomes a red giant (up and to the right of the MS on the HR diagram)
 * Since there is NO electron degeneracy, there is only gradual heating in the core, and NO helium flash
 * Once the He is used up in the core (fused to Carbon via the triple alpha process), the core collapses, and as there **isn't** enough mass to provide the pressure to drive the temperature up to what is needed for carbon fusion, the core collapses.
 * This collapsed core is a "white dwarf" ("white" hot) that ionizes the surrounding layers, which expand as a planetary nebula.
 * A cooling white dwarf will eventually crystallize to a diamond.
 * __ High Mass Stars (8 - 25 solar masses) __ :
 * These stars have "chemically separate cores and shells."
 * When core hydrogen is used up, there is no outward radiation pressure to counteract the gravitation collapse, so the star collapses.
 * This increases the pressure throughout the star, and the temperature throughout the star increases.
 * H fusion begins in a shell surrounding the core and the star's outer regions expand due to this increase in temperature.
 * The star becomes a red giant (up and to the right of the MS on the HR diagram)
 * Since there is NO electron degeneracy, there is only gradual heating in the core, and NO helium flash
 * Once the He is used up in the core (fused to Carbon via the triple alpha process), there is no outward radiation pressure to counteract the gravitation collapse, so the star collapses.
 * This increases the pressure throughout the star, and the temperature throughout the star increases.
 * Since there **is** enough mass to (create the pressure to drive the temperature up high enough to) fuse carbon in the core, carbon starts fusing.
 * These successive fusion processes continue until iron is the fusion product in the core.
 * Iron can't fuse, so the core collapses.
 * This core environment is so hot, photodisintegration breaks up all the iron nuclei into protons, neutrons and electrons. The electrons fuse with the protons, making yet more neutrons, and a neutron core is formed.
 * The upper layers of the star collapse towards this neutron core, but rebound when they hit the non-compressible "surface" of the neutron core.
 * The material of these outer layers rebound and speed through space in a type II supernova explosion.
 * The neutron core, once exposed, is a neutron star.
 * A spinning neutron star is called a pulsar.
 * __ High Mass Stars (more than 25 solar masses) __ :
 * These stars have "chemically separate cores and shells."
 * When core hydrogen is used up, there is no outward radiation pressure to counteract the gravitation collapse, so the star collapses.
 * This increases the pressure throughout the star, and the temperature throughout the star increases.
 * H fusion begins in a shell surrounding the core and the star's outer regions expand due to this increase in temperature.
 * The star becomes a red giant (up and to the right of the MS on the HR diagram)
 * Since there is NO electron degeneracy, there is only gradual heating in the core, and NO helium flash
 * Once the He is used up in the core (fused to Carbon via the triple alpha process), there is no outward radiation pressure to counteract the gravitation collapse, so the star collapses.
 * This increases the pressure throughout the star, and the temperature throughout the star increases.
 * Since there **is** enough mass to (create the pressure to drive the temperature up high enough to) fuse carbon in the core, carbon starts fusing.
 * These successive fusion processes continue until iron is the fusion product in the core.
 * Iron can't fuse, so the core collapses.
 * This core environment is so hot, photodisintegration breaks up all the iron nuclei into protons, neutrons and electrons.
 * The upper layers of the star collapse towards this neutron core, and as there is SOOOOOO much mass, the pressure crushes the neutrons.
 * This crushed core is a black hole.
 * Some outer layers still rebound and speed through space in a type II supernova explosion.
 * __Variable Stars:__
 * RR Lyrae
 * Medium mass stars, post helium flash pass through the RR Lyrae variable star stage.
 * Light curves show periodicity of less than one day
 * Cepheids
 * Leavitt law possible due to period-luminosity relationship. The longer the period, the luminous the star
 * Very bright, and can be seen in distant galaxies, used as a standard candle.
 * __Binary star evolution__:
 * In close binary star systems, mass (H) can be transferred from an evolved (bloated red giant) to it's companion.
 * If this companion is a white dwarf, the mass transfer causes layers to H to build up on the white dwarf.
 * This material can spontaneously fuse if/when enough mass (that creates the pressure, that drives up the temperature) builds up.
 * Novae, or sometimes type I supernovae can result.
 * A nova does not destroy the white dwarf, only the layers of added H.
 * A type I supernova completely destroys the white dwarf.
 * Type I supernovae are brighter than type II supernovae and the type I's are used a standard candles.
 * gamma ray bursts: long bursts and short bursts
 * different "sizes" of black holes, escape velocity of a black hole, what it would be like to go near a black hole (not recommended).