Lecture 8
The Sun

The closest star

Mythology

Every culture has revered the Sun

e.g., Aztec sunstones (1, 2) and art (1, 2)

 

Thermal Radiation and the Blackbody Spectrum

Review physics of Lecture 5 on light:

• Energy output table
• Electromagnetic Spectrum [Chaisson Fig.3.9]

 

Blackbody spectrum (Chaisson Section 3.4)

• Intensity-versus-Wavelength graph
• or Chaisson plots as Intensity-versus-Frequency graph ( Fig3.11 )
• examples of Blackbody Spectra (Fig.3.12 cool gas cloud, young star, Sun, hot bright star cluster)

Solar blackbody spectrum

Solar absorption line spectrum

 

 

Structure of the Sun

Components I want you to know are Photosphere, Corona, Solar Wind, as well as the Core.
c.f., overall structure (Chaisson Figs 16.2 and 16.7) and propterties (Chaisson Table 16.1)

 

(2006 Solar eclipse composite showing 3 of the 4 components)

 

Photosphere

• granules
• sunspots (Galileo and now)
• sunspot cycle (11 year cycle, and longer cycles).
  Last few decades significant increase in activity.
  Compare with late 1600's "little ice age"

 

Corona

• visible during eclipse
• solar flares and loops (image)
• studied by satellites: SOHO and TRACE . Insane number of cool pix

 

Solar Wind

• spaceweather
• affects Earth's magnetosphere (e.g., during flares and prominences, SOHO gallery ) causing Aurora

 

Core

• Thermo-nuclear fusion reactions (Chaisson material and pix in section 16-6)

 

Reading/Bibliography

Chaisson text:

• Chapter 3 (section 4, Thermal radiation and the Blackbody Spectrum)
• Chapter 16

Aztec Tenochtitlan

Curious, albeit apocryphal webpage about the surface of the Sun

 

Document URL: http://www.uh.edu/~jclarage/astr3131/lectures/8/8.html