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Stars (The Sun (Sol) (Layers (Photosphere: (Temp 5,780 K, Visible "…

- - - - by mass
        
        2% other
        
        25% helium (He)
        
        73% hydrogen (H)
    - - equilibrium between gravity & pressure from hot expanding gas
        
        Gas pressure caused by nuclear fusion within the core
        
        Temperature: 15,000,000 degrees Kelvin
    - - Diameter
        
        109 Earths
      - Mass
        
        333,000 Earths
    - - 4 x 10^26 Watts
    - - Roughly an 11 year cycle
  - - - Energy leased as gamma rays
      - Step 1:
        
        2 protons smash together at extreme speed & fuse
        
        1 changes to a neutron
        
        Ends with a Deuterium nucleus
        
        2H: 1 proton & 1 neutron
        
        The rest is released as energy
      - Step 2:
        
        Deuterium nucleus impacts another proton
        
        Makes Helium-3
        
        3He: 2 protons & 1 neutron
        
        More energy release
      - Step 3:
        
        2 Helium-3 nuclei collide
        
        Making Helium-4 nucleus
        
        4He: 2 protons & 2 neutrons
        
        Helium-4 has less mass than 4 protons
        
        Some of the mass is converted into gamma-ray photons
        
        Releases 2 protons & more energy
      - Takes a lot of energy to start chain
        
        However, more energy is created at each step
        
        E=mc^2
        
        E = energy
        
        m = mass
        
        c = the speed of light
        
        A constant
  - - - Center, highly Dense, extreme Temps, Nuclear Fusion, Gamma Rays produced
    - - Photons cycle
        
        Single photon may take 170,000 years to escape
    - - Rising hot gas, sinking cold
        
        Light takes roughly 1 week to get through
    - - Temp 5,780 K
      - Visible "surface"
      - Photons transformed into visible wavelengths/temperature
      - "Granules" visible because of convection
    - - Temp 4,500 K
      - Red & Orange
      - Transparent
    - - Magnetic activity that causes an eruption out of the Sun
    - - Magnetic activity that causes a hoop eruption out of the Sun
    - - Low Density
      - Temp 1 million K
      - Only visible during full solar eclipse
    - - Reaches to the end of the Solar System
      - Ejection of charged particles
- - - - Power produced at the surface
    - - Perceived output from a distance (d)
    - - B = L/4 pie d^2
        
        B ~ L/d^2
        
        Example 2: If star A is 9 times as L as star B, then stars A & B would appear equally B if star A were 3 times as far as star B
        
        Example 1: If 2 stars have the same L but 1 is 10 times further away, then it will appear 1/10^2 times as B
  - - - View a star from 2 locations, for best results from the earth, like on opposite sides of the Sun, looking for small changes in the star's apparent position.
        
        Location in Earth's orbit at opposed sides of "baseline"
        
        Same as holding your finger up in front of your line of sight while switching looking between each eye
        
        One's finger will appear to move more than objects in the distance.
    - - D = 1 / p
        
        D = distance in parsecs
        
        p = parallax angle in arcseconds (1 /3600 degree)
        
        Example 1: A star has a p of 0.1 is 1 / 0.1 = 10 parsecs away
        
        Example 2: A star has a p of 0.02 is 1 / 0.02 = 50 D parsecs away
    - - ,Baseline is 1 Astronomical Unit (AU)
        
        Average distance between Earth & Sun
- - - - Surface Temp
        
        Estimated w/Spectral Class
        
        O - B - A - F - G - K - M from hotter to cooler
        
        Oh, Be A Fine Girl, Kiss Me
        
        Determined by absorption spectrum
        
        Since different chemical elements w/differing ionization levels arise at different temperatures produce absorption lines
      - Increases right to left
        
        Cooler, on right, are redder
        
        2,300 K
        
        Hotter, on left, are blue
        
        40,000 K
    - - Luminosity
        
        Stated in terms of luminosity of the Sun
  - - - Closest at 4.3 light years (1.35 parsecs)
      - Apart of a triple star system w/ brightest like the Sun
    - - Most stars are like this
  - - - Appears the brightest
        
        Twice as large as Sun
        
        Has a white dwarf binary companion
- - - - L ~ R^2 x T^4
      - a larger size = larger light-emitting surface area = greater luminosity
      - Higher temp = much greater luminosity (also bluer)
  - - - Determines lifespan
      - Mass ranges from 0.1 to 100 times the Sun's
        
        Greater mass use more fuel over a set period of time
      - Radius or size range from 0.1 to 15 times the Sun's
        
        Largest stars live for a few million years
        
        Smallest live for more than the current age of the Universe
    - - Red Giants & Supergiants
        
        Burn helium or heavier, not hydrogen
        
        Beginning to die
        
        Size is large
        
        Thus, very luminous in spite of being cool
        
        Top right of H-R diagram
      - White Dwarfs
        
        Hot
        
        Small & dim
        
        Bottom left of H-R diagram
        
        Low-mass stars' left over cores cooling & fading