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astronomythesun (The Sun ** )

Astronomy — The Sun

The Sun

  • Our Sun is about 5 billion years old, and it will burn for about another 5 billion years.  Thus, it is about halfway through its life cycle.
  • It is 93,000,000 miles from Earth.
  • It is 75% hydrogen by mass and 24% helium by mass.  It contains 67 of the roughly 100 elements found on earth.
  • It is 865,000 miles in diameter, and it contains 99.86% of all the mass in our solar system.
  • Its surface temperature is 5800 degrees Kelvin, or about 10,000 degrees Fahrenheit.
  • The Sun’s core temperature is 30 million degrees Fahrenheit.
  • Every minute, the Sun converts 564 million tons of hydrogen into 560 million tons of helium, releasing 4 million tons of radiant energy.
  • It takes the Sun 250 million years to complete one turn around our Milky Way Galaxy.
  • Since the Sun is about 5 billion years old, it has completed 20 turns around the center of the galaxy.
  • The average visual diameter of the Sun as seen from earth is 0.53 degrees or 32 minutes.
  • The Sun rotates on its axis once every 25 days (Earth days).
  • The apparent magnitude of the Sun is -27.  The absolute magnitude is 4.8. If the Sun was 10 parsecs away, it would be no brighter than the faintest star in the Little Dipper.
  • When the Sun began its main sequence life about 5 billion years ago, it was only 60% as bright as it is now, and by the time it leaves main sequence 5 billion years from now, it will be twice its present luminosity.  This will raise the Earth’s temperature by 34 degrees Fahrenheit, melt the polar ice caps, evaporate the oceans away, and burn off the atmosphere.
  • Solar eclipses:
    1. Because the cone of shadow cast by the moon is just long enough to reach the earth, a total eclipse is seen in a narrow band (170 miles).
    2. The umbra sweeps across the Earth at 1000 mph
    3. An annular eclipse occurs when the Moon appears too small to completely cover the face of the Sun.
    4. The Sun is 400 times larger than the Moon, and 390 times farther away from the Earth than is the Moon, so they have nearly equal angular diameters, equaling 0.5 degrees
  • Sunspots:
    1. Caused by disturbances in the Sun’s strong magnetic field
    2. They are 2000 degrees cooler than the surrounding area
    3. They occur in 11 year cycles between minimum and maximum activity levels
    4. The average ‘spot’ is about twice the diameter of Earth and lasts about 1 week
    5. They tend to form in groups
    6. The spot’s magnetic field is 1000 X stronger than the Sun’s average magnetic field
  • Solar flares:
    1. Flares and prominences occur when sharp twists in the magnetic field store up great quantities of energy and release it all at once
    2. Flares cause X-ray and UV radiation which increases the ionization in the Earth’s upper atmosphere and alters the reflection of shortwave radio signals
    3. Flares can also eject low velocity particles which reach Earth hours or days after the flare, and then interact with Earth’s magnetic field, generating tremendous electrical currents which flow down toward Earth at the poles.  This is the cause of auroras.
  • The Sun’s outer layers:
    1. The photosphere is the thin layer of gas from which we receive most of the Sun’s light.  It is 330 miles deep and 6000 degrees Kelvin.  Comparing the Sun to a bowling ball, the photosphere would be a layer the width of tissue paper wrapped without wrinkles around the ball.
    2. Granulations are caused by rising and sinking gas currents just below the photosphere
    3. The chromosphere is 6600 miles deep, 10,000 degrees Kelvin, and 1000 times fainter than the photosphere
    4. The corona is the Sun’s atmosphere extending above the chromosphere.  It is 1 million degrees Kelvin and 5 atoms per cubic centimeter dense.  The extreme heat results from interaction with the Sun’s rotation and magnetic fields.
    5. The solar wind is a stream of high-velocity gas atoms, blowing past the Earth at 200 to 350 miles per second in irregular gusts
  • The Sun transforms 5 millions tons of its mass into energy every second, but in its entire 10 billions year lifetime, it will convert only 1% of its total mass into energy!

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