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Sun

Position in the Sky

Calculating positions in the sky

The Sun in the sky depending on the season

  • Motions of the Sun Simulator
  • Rises East --> sets West
  • Depending on the time of year, we can use the altitude to calculate the Sun's position in the sky
  • Maximum height when crossing the meridian at local noon
  • Local noon
    • Northern hemisphere --> due south
    • Southern hemisphere --> due north
    • Equator --> either north or south depending on time of year
  • Declination ranges between -23.5˚ and +23.5˚

Atmosphere

Layers of the Sun

Composition

  • Spectroscopic data analyzed in 1925 helped confirm composition
  • Mostly hydrogen and helium
  • Most elements are in the form of atoms
    • So much heat, many of the atoms are ionized
      • Stripped of one or more of their electrons
        • Large quantity of free electrons and positively charged ions
        • An electrically charged environment
      • Hot ionized gas --> plasma
  • Proton-proton Chain
  • Core
    • Extremely dense
    • Source of all its energy
    • Approximately 20% of the interior
    • Temperature of 15 million K
      • Hottest part of the Sun
  • Radiative zone
    • Photons carry energy and hit particles transferring energy
    • How energy goes from inside --> outside
    • Light from the core is transported through this zone very slowly
      • High density
      • Photons encounter other particles and change direction or lose some energy
  • Convective zone
    • Hot blobs of gas moving out
    • Outermost layer of the interior
  • Hydrostatic equilibrium

Prominences, Flares, and Coronal Mass Ejections

  • Prominences
    • Usually originate near sunspots
    • Look like loops or eruptions from the surface
    • Ionized gas
  • Solar flares
    • Most violent event on the Sun's surface
    • Rapid eruption lasting 5-10 minutes
    • Releases a total amount of energy equal to that of a million hydrogen bombs
  • Coronal mass ejection
    • Mostly protons and electrons released from the corona
    • Speeds between 500-1000 km per second

Energy

  • Outputs about 4×10254 \times 10^{25} watts of energy
  • When Albert Einstein discovered that mass can be considered energy, and converted into energy, the mysteries behind the Sun's power were unlocked

Space Astronomy