Light, Astronomical Observations, and the Sun

1. Light, Astronomical Observations, and the Sun

2. Terms • Spectrum • A range of something, e.g. colors • Spectra • Plural of spectrum • Incandescent • Hot enough to glow (emit visible light radiation)

3. Terms • Wavelength (λ) • Length of one wave from peak to peak • Shorter wavelength = more energy • For visible light • Shorter wavelength = BLUE • Longer wavelength = RED

4. Terms • Light-year • Distance traveled by light in one year • 5,900,000,000,000 miles • Measure of distance, not time

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

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

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

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

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

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

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

12. Visible Light Spectra PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy • 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

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

14. Visible Light Spectra PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy • 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

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

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

17. Continuous Spectrum Shows Total Energy PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy • Proportional to fourth power of object’s surface temperature • Example: if Star B is twice as hot as Star A… • …Star B emits 2 x 2 x 2 x 2 = 16 times more energy that Star A

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

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

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

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

22. The Doppler Effect PSCI 131: Light, Astr. Observations, & The Sun Sheldon’s Doppler Effect costume

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

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

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

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

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

28. Optical Telescopes: Refracting PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes From: www.odec.ca

29. Optical Telescopes: Refracting PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes • 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

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

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

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

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

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

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

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

37. The Hubble Space Telescope PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes Type: Reflecting Years in operation: 24 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

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

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

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

41. The Sun’s Layers PSCI 131: Light, Astr. Observations, & The Sun – The Sun 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

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

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

44. Photosphere: closeup view PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers Source of visible light Covered by granules produced by convection “Boiling” appearance Movie: Visiting the photosphere for one hour From: www.astronomynotes.com

45. The Sun’s Engine PSCI 131: Light, Astr. Observations, & The Sun – The Sun • 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)

46. End of Light & The Sun Chapter