1. Light, Astronomical Observations, and the Sun

2. Light, Astronomical Observations, & the Sun
PSCI 131: Light, Astronomical Observations, & The Sun
Light, Astronomical Observations, & the Sun
Signals From Space
Spectroscopy
The Doppler Effect
Optical Telescopes
Radio and Orbiting Telescopes
The Structure of the Sun

3. Signals from Space The electromagnetic (EM) spectrum
PSCI 131: Light, Astronomical Observations, & The Sun
Signals from Space
The electromagnetic (EM) spectrum
Energy waves (radiation) emitted by matter

4. PSCI 131: Light, Astr. Observations, & The Sun – Signals from Space
The EM Spectrum

5. EM Radiation from Celestial Objects
PSCI 131: Light, Astr. Observations, & The Sun – Signals from Space
EM Radiation from Celestial Objects
EM energy is emitted from many objects
Stars, black holes, supernovas (exploding stars), etc.
Not the same as reflected energy
Moons, planets, etc. reflect light energy from stars

6. EM Radiation from Celestial Objects
PSCI 131: Light, Astr. Observations, & The Sun – Signals from Space
EM Radiation from Celestial Objects
Emitted radiation can be collected and used to study the object
Telescopes: optical, radio, space-based
Spectroscopy

7. PSCI 131: Light, Astr. Observations, & The Sun
Spectroscopy

8. Spectroscopy Using radiation from an object to learn about that object
PSCI 131: Light, Astronomical Observations, & The Sun
Spectroscopy
Using radiation from an object to learn about that object
Most astronomical observations can only use radiation
Most objects too far away to visit

9. PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
Visible Light Spectra
Visible light can be split into its component wavelengths (colors)
Creates continuous, bright-line, and dark-line spectra
Spectra can give key information about the object the light came from

10. PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
Visible Light Spectra
(Low-temp)
(Incandescent)
CONTINUOUS
BRIGHT-LINE
DARK-LINE

11. PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
Visible Light Spectra
Visible light can be split into its component wavelengths (colors)
Creates continuous, bright-line, and dark-line spectra
Spectra can give key information about the object the light came from

12. Continuous Spectrum Shows surface temperature of object
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
Continuous Spectrum
Shows surface temperature of object
Shows total energy emitted by object

13. Continuous Spectrum Shows Surface Temp
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
Continuous Spectrum Shows Surface Temp
exaggerated
COOLER
HOTTER

14. Continuous Spectrum Shows Total Energy
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
Continuous Spectrum Shows Total Energy
Proportional to fourth power of object’s surface temperature
Example: if Star B is five times as hot as Star A…
…Star B emits 54, or 5 x 5 x 5 x 5 = 625 times more energy that Star A

15. PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
Dark-Line Spectrum
Light from star’s interior passes through gas composing star’s exterior
Interior
Exterior gases

16. Dark-Line Spectrum Shows what elements are present in object
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
Dark-Line Spectrum
Shows what elements are present in object
Each element absorbs a unique pattern of visible light wavelengths
From: mail.colonial.net 

17. Dark-Line Spectrum Shows what elements are present in object
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
Dark-Line Spectrum
Shows what elements are present in object
Each element absorbs a unique pattern of visible light wavelengths
From: mail.colonial.net 

18. Bright-Line Spectrum Shows what elements are present in object
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
Bright-Line Spectrum
Shows what elements are present in object
Each element emits a unique wavelength pattern when heated
From: intro.chem.okstate.edu

19. PSCI 131: Light, Astronomical Observations, & The Sun – Doppler Effect
The Doppler Effect
Apparent shift in wavelength relative to a stationary observer
The Doppler Effect with sound waves. Longer apparent wavelength = lower frequency.

20. Red and Blue Shift Light waves undergo Doppler Effect
PSCI 131: Light, Astronomical Observations, & The Sun – Doppler Effect
Red and Blue Shift
Light waves undergo Doppler Effect

21. Red/Blue Shifts Change Dark-Line Spectra
PSCI 131: Light, Astronomical Observations, & The Sun – Doppler Effect
Red/Blue Shifts Change Dark-Line Spectra
Star moving away from Earth = RED shift
Star approaching Earth = BLUE shift

22. PSCI 131: Light, Astr. Observations, & The Sun
Optical Telescopes

23. Optical Telescopes Gather visible light radiation
PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes
Optical Telescopes
Gather visible light radiation
Concentrate it at a focal point, creating magnified image
Two types
Refracting
Reflecting

24. Optical Telescopes: Refracting
PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes
Optical Telescopes: Refracting
From:

25. Optical Telescopes: Refracting
PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes
Optical Telescopes: Refracting
Advantages
Inexpensive
Lens doesn’t have to be perfect to make a decent image
Drawbacks
Chromatic aberration reduces image quality, limits maximum telescope size
Chromatic aberration: “halo” of color around image caused by refracted light

26. Optical Telescopes: Reflecting
PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes
Optical Telescopes: Reflecting
From: odec.ca

27. Optical Telescopes: Reflecting
PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes
Optical Telescopes: Reflecting
Advantages
No chromatic aberration
Can be very large, so higher magnification
Drawbacks
More expensive
Tiny flaws in mirror can greatly reduce image quality
From:

28. Radio & Orbiting Telescopes
PSCI 131: Light, Astr. Observations, & The Sun
Radio & Orbiting Telescopes

29. Radio Telescopes Gather radio waves from space
PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes
Radio Telescopes
Gather radio waves from space
These signals are extremely faint
Collecting dish must be very large

30. PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes
Radio Telescopes
From: amazing-space.stsci.edu 

31. Radio Telescope at Arecibo, Puerto Rico
PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes
Radio Telescope at Arecibo, Puerto Rico
World’s largest & most sensitive R.T.
Diameter: 1000 ft
Depth: 167 ft
Weight of receiver: 900 tons

32. Orbiting Telescopes Optical, radio, gamma-ray, X-ray, infrared
PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes
Orbiting Telescopes
Optical, radio, gamma-ray, X-ray, infrared
No atmospheric or human “noise”

33. The Hubble Space Telescope
PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes
The Hubble Space Telescope
Type: Reflecting
Years in operation: 25
Orbit height: 347 miles
Orbital speed: 25,000 ft/sec
Length: 43 ft
Mirror diameter: 7.9 ft
Farthest object observed:
13 billion light years away
(76,700,000,000,000,000,000,000 miles)
From: nasa.gov

34. PSCI 131: Light, Astr. Observations, & The Sun
Structure of the Sun

35. The Sun’s Composition Form: gaseous
PSCI 131: Light, Astr. Observations, & The Sun – The Sun
The Sun’s Composition
Form: gaseous
Density: slightly greater than water
Hydrogen: 90%
Helium: almost 10%
Other trace elements: less than 1%

36. The Sun’s Emissions The sun emits two things into space:
PSCI 131: Light, Astr. Observations, & The Sun – The Sun
The Sun’s Emissions
The sun emits two things into space:
Radiation, including visible light
Solar wind, streams of protons & electrons

37. PSCI 131: Light, Astr. Observations, & The Sun – The Sun
The Sun’s Layers
Numbers are in order of increasing depth
2. CHROMOSPHERE
5. RADIATION ZONE
4. CONVECTION ZONE
6. CORE
3. PHOTOSPHERE
1. CORONA
Modified from: visual.merriam-webster.com

38. Corona (during solar eclipse)
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers
Corona (during solar eclipse)
From: mreclipse.com

39. PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers
Chromosphere
From: astroguyz.com

40. Photosphere: closeup view
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers
Photosphere: closeup view
Source of visible light
Covered by granules
produced by convection
“Boiling” appearance
Photosphere time lapse
From:

41. The Sun’s Engine Matter is converted to energy in the core
PSCI 131: Light, Astr. Observations, & The Sun – The Sun
The Sun’s Engine
Matter is converted to energy in the core
Nuclear fusion reactions
Hydrogen + hydrogen = helium + energy
4 billion tons per second
E = mc2
c: speed of light (186,000 miles/second)

42. End of Light & The Sun Chapter