10/19/2011
The Nature of Light Sun
Tools of Astronomy
Electromagnetic Spectrum
Spectrum
Continuous Spectrum
• From glowing gas under pressure
• Like the interior of Sun
Dark Line Spectrum
• White light passing through cold, low pressure gas
• Gas absorbs its elemental wavelength signature
1
10/19/2011
Bright Line Spectrum
3 types of spectra
• Incandescent hot gas emits its elemental wavelength signature
How much of the electromagnetic spectrum is visible light?
1. All of it
2. Most of it
3. Only a tiny fraction
4. None of it
25%
1
25%
25%
2
3
Sun
25%
Photo of Sun’s granular surface
4
Detail of Sunspot
2
10/19/2011
Group of Sunspots
Sunspot Variation over time
Spicules of the Chromosphere
Solar Corona
Solar wind blows comet tails
Solar Prominence
http://www.astro.uva.nl/demo/sun/inter.htm
http://antwrp.gsfc.nasa.gov/apod/image/0109/sunplume_soho_big.gif
Video clip http://antwrp.gsfc.nasa.gov/apod/ap030223.html
Another video clip http://spacescience.com/headlines/images/prominence/prominence_10jan00.mov
3
10/19/2011
Auroras
Aurora photo from Skylab
http://www.astro.uva.nl/demo/sun/aarde.htm
Surface Detail of Sun
Solar Interior
• Nuclear Fusion of 4 Hydrogen to 1 Helium
• Difference in atomic mass is released as energy
• Released as photons—light particles
R l
d
h
li h
i l
• Convection brings photons to photosphere
• Sun will last about another 5 billion years
Structure of Sun
Sun Structure
• Photosphere: most visible part— “Surface”
– Hydrogen and helium
– Granules, sunspots
• Chromosphere: lower atmosphere
– Spicules from granules of photosphere
– prominences
• Corona: outer atmosphere
– Ionized gases
– Solar wind
• Solar flares
– Create auroras
– Associated with sunspots
4
10/19/2011
This page was copied from Nick Strobel's Astronomy Notes. Go to his site at www.astronomynotes.com for the updated and corrected version This page was copied from Nick Strobel's Astronomy Notes. Go to his site at www.astronomynotes.com for the updated and corrected version Sun now and later
Red Giant Betelgeuse
Nebula—eventual Sun
Main Sequence to Red Giant to White Dwarf
http://www.astro.uva.nl/demo/sun/leven.htm
The Nature of Light
• Light is made of photons
• Photons act as particles
• Photons act as waves
http://imagine.gsfc.nasa.gov/docs/science/know_l2/dwarfs.html
Waves
• Movement of energy, not of matter
5
10/19/2011
Overlapping ripples
Waves are movement of energy
• The matter pretty uc stays put
much stays put
•
Video link below, clip #142‐69
http://www.4oliveus.com/land_4_sale/images/L_Wave_of_Grass.jpg
http://creative.gettyimages.com/source/frontdoor/DefaultFilm.aspx
Trace of pendulum
Wave terminology
http://cimss.ssec.wisc.edu/satmet/modules/spectrum/wavelength.html
Wave Description
Electromagnetic Spectrum
• Wavelength—distance from one part of the wave to the same part of the next wave
• Crest—top
Trough bottom
• Trough—bottom
• Amplitude—distance from midway between crest and trough, to the crest or trough
• Period—time for one complete wave to pass
• Frequency—how often the wave passes
6
10/19/2011
Ripples
Stationary Bug
Moving Bug
Doppler Effect of Siren
http://www.yenra.com/banner‐ad‐effectiveness/
• Doppler effect of a whistle in the youtube link
http://www.youtube.com/watch?v=NvBvTuOxU‐0
Doppler effect of movement on the reception of wave forms
Effect of Red Shift on Na Spectrum
7