The Sun and the Solar System

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The Sun and the Solar System

• Chapter 26

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24.3 Suns Size, Heat and Structure

• Diameter 1,400,000 km or 868,000 miles
• More than 3x the distance of Earth to moon
• More than 1 million Earths could fit in sun
• Energy
• All stars get their energy from fusion
• Fusion- combining of nuclei of lighter elements
  to form a heavier element
• Star is place of intense heat and pressure
• Plasma- 4th state of matter consisting of charged
  particles (positively charged ions/ negatively
  charged electrons)

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Fusion

• Mass before is greater than mass after
• Missing mass is converted to energy

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Suns Layers

• Core hydrogen and helium in a plasma state
  (15,600,000C)
• Radiation zone plasma- temp. range 8,000,000-
  2,000,000 C)
• Convection zone rising and falling currents of
  plasma that carry energy to the suns surface

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Suns Layers cont

• Photosphere visible surface of sun
• Granules- tops of convection currents
• 6,000 C
• Chromosphere inner layer of suns atmosphere
• 20,000 C (reddish)
• Solar prominences
• Corona outer atmosphere
• 1,000,000 to 3,000,000 C
• Examine the sun at different wavelengths.

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Features on the Sun

• AU- astronomical unit- distance from sun to Earth
  (150 million km)
• Sunspots- dark spots on photosphere
• Dark because surrounding photosphere is hotter
  and brighter
• Magnetic field is 1000x stronger than surrounding
  photosphere
• Move from left to right
• Evidence that the sun rotates
• Cycle of about 11 years

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Sunspots
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Magnetic Field
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Solar Wind and Magnetic Storms

• Solar wind- stream of electrically charged
  particles from corona
• coronal holes- large openings
• Solar flares- most explosive feature on the sun!
• Increase in sunspots increase in solar flares
• Earths magnetic field deflects solar winds
• Auroras- displays of color and light appearing in
  upper atmosphere
• Magnetic storms occur when more particles are
  added to constant solar wind from corona
• may disrupt radio communications

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22.1 History of S.S.

• Geocentric- Earth-centered model
• Celestial sphere that surrounded Earth
• Used constellations for calendar
• Planets closer to Earth than stars
• Retrograde motion- moved eastward, then westward
  for a few weeks

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Important People
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Ptolemy

• Greek astronomer in 2nd century AD
• Puzzled by retrograde motion
• Developed a system to predict planetary position
• Planets on epicycles- small circular orbits
• Deferent is the larger circular orbit
• Retrograde Motion

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Important People
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Nicolaus Copernicus

• Polish astronomer (1473- 1543)
• Developed heliocentric model- sun- centered
• Retrograde motion appears as Earth overtakes Mars
• Retrograde Motion

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Important People
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Tycho Brahe

• 16th century Danish noblemen
• Studied movements of planets in their orbits
• Very precise measurements without aide of
  telescope
• Passed away before he could apply data

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Important People
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Johannes Kepler

• German (1571-1630) Tychos assistant
• Laws of planetary motion
• 1st- planets travel in elliptical orbits with sun
  at one foci
• 2nd- equal area law- a line connecting Earth to
  the sun will pass over equal area of space in
  equal times
• 3rd- harmonic law- the period (P) of a planet
  squared is equal to the cube of its mean distance
  (D) from the sun, or P2 D3
• Kepler's Laws with animation

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Important People
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Isaac Newton

• English scientist and mathematician (1642- 1727)
• Developed explanation for what kept the planets
  in motion
• 3 laws of motion and law of gravitation
• 1st law- an object will move forever in a
  straight line at the same speed unless some
  external force changes its direction or speed
• Law of gravitation- every mass exerts a force of
  attraction on every other mass, and the strength
  of that force is proportional to each of the
  masses and inversely proportional to the distance
  between them

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Important People
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Galileo Galilei

• Italian scientist (1564-1642)
• With the aide of the first known telescope he
  discovered the following
• Four Galilean moons of Jupiter
• Planets are circular disks, not just points of
  light
• Venus has phases just like the moon
• The moons surface was not smooth
• The sun has sunspots, or dark regions