1. Electromagnetic Spectrum Lecture

2. Standards
Explain how objects in the universe emit different electromagnetic radiation and how this information is used
Examine the role that NM research facilities play in current space exploration (e.g., Very Large Array)
Understand how knowledge about the universe comes from evidence collected from advanced technology (e.g., telescopes)
Describe wave propagation using amplitude, wavelength and frequency

3. Electromagnetic Radiation
Electromagnetic Radiation - another term for light.
It transfers energy and information from one place to another.

4. Electromagnetic Spectrum
The range of electromagnetic radiation: radio waves, infrared, visible, ultraviolet, x-rays and gamma rays.
These all differ in wavelength
They all travel the same speed in a vacuum: 300,000 km/s or 186,000 mi/s. This is the speed of light, denoted by c.
Snap your fingers
In the time it takes you to snap your fingers, light travels ¾ of the way around the earth.

5. The Electromagnetic Spectrum

7. Electromagnetic Spectrum
Radiation is the way in which energy is transmitted through space from one point to another without the need for any physical connection between the two locations.
Electromagnetic means that the energy is carried in the form of rapidly fluctuating electric and magnetic fields.

8. Electric & Magnetic Wave Fields

9. Electromagnetic Spectrum
Visible light is the wavelength that human eyes are sensitive to
We experience sight when:
Light enters the eye
The cornea and lens focus it onto the retina
An electrical impulse goes to the brain, giving us the sensation of sight

10. Wave Motion
All electromagnetic radiation travels through space in the form of waves.
Energy is transferred from one place to another without the movement of the material it’s traveling through.
Waves do not need a medium (i.e., substance) to travel through.

11. Wave Motion Draw the following wave and label its parts
This is a transverse wave
Crest
Resting point
Wavelength
Amplitude
Trough
Frequency = # waves
second

12. Wave Motion
Wavelength is measured in units of Ångstroms (Å) (older unit) or nanometers (nm)
There are 109 nm in 1 meter:
109 = 1,000,000,000

13. Wave Motion
Visible wavelengths range from 400 – 700 nm or 4000 – 7000 Å.
Your eyes are most sensitive to the 550 nm, or 5500 Å wavelength.
This is yellow-green: the newer color of fire trucks and school crossing signs.
The sun emits most of its energy in this wavelength.

14. Parts of the Electromagnetic Spectrum
Radio
Infrared
Visible
Ultraviolet
X-rays
Gamma rays

15. Radio Waves Longest wavelengths, therefore lowest energy 1 cm to 108 m
Includes radar, microwave, AM, FM and TV

16. Radio Waves Radio telescopes collect and concentrate radio waves
They are giant antennas
Radio waves were discovered in 1930
By 1940, the radio sky was charted
Technology was developed because of WWII

17. Radio Waves Radio telescopes can observe 24 hours a day
Can observe parts of the universe that can’t be seen optically
Ex: black holes. Never observed before radio astronomy

18. SgrA: black hole at center of Milky Way
Photo: UC Berkely,

19. Radio Waves Radio telescopes have poor angular resolution
Resolution = the ability to distinguish between objects that are close together.
Higher resolution = better detail.
Interferometry –technique where two or more telescopes are put together to increase resolution.
They look at the same object, in the same wavelength, at the same time

20. Radio Telescopes VLA = Very Large Array
Radio telescopes located on San Agustin Plains near Socorro, NM
Located at 7000 ft and isolated in mountain ranges to block interference from other radio sources.
World renowned astronomers come here from all over the world.

21. Radio Telescopes
28 antennas (27 working, one for replacing during repairs)
Arranged in a Y-shaped configuration
Each telescope is 25 meters in diameter (about length of classroom) and weighs 235 tons
Receivers are cooled to -430 F to get rid of interference.

22. VLA Y-Shaped Configuration
Photo:
Crystal_Radio/VLA.jpg

23. Photos: L. Brown, June 2007

24. Photo: L. Brown, June 2007

25. Photo: L. Brown, June 2007

26. VLA Under Radio Sky Photo: NROA, http://www.cv.nrao.edu/
~abridle/images.html

27. Radio Telescopes
National Radio Astronomy Observatory, Green Bank, West Virginia
World’s largest moveable radio telescope
43 m in diameter & 150 m tall (taller than Statue of Liberty)
Original structure collapsed, has been rebuilt

28. Photo: APOD, http://antwrp.gsfc.nasa.gov/apod/ap020311.html

29. Radio Telescopes Arecibo Observatory, Puerto Rico
World’s largest radio telescope
300 m in diameter
Surface spans nearly 20 acres

30. Photo: http://www.evlbi.org/evlbi/te024/te024.html

31. Photo: http://commons. wikimedia

32. Radio Telescopes Very Long Baseline Array
10 radio telescopes spanning 5,351 miles
World’s largest and sharpest (you could be in Los Angeles and clearly read a street sign in New York City
Used to observe quasars, black holes and stars in every stage of stellar life cycle

33. Very Long Baseline Array

34. Radio Telescopes
Atacama Large Millimeter/submillimeter Array (ALMA) (still being built)
Highest array at 16,500’
In Atacama desert, Chile
At least 66 telescopes
Maximum range = 71,000 square feet of radio light collecting area
Largest leap in telescope technology since Galileo first aimed a lens on the universe

35. ALMA

36. Infrared (IR)
Wavelengths are just longer than we can see without special goggles
Infrared radiation is heat (produced by many objects)
It is used in the medical field, police work, military…(night vision goggles)

37. Infrared (IR)
Infrared telescopes are placed in high, dry areas because Earth’s atmosphere interferes with IR radiation
Telescopes need to be cooled down close to absolute zero
Equipped with a bolometer, made of germanium, to detect the IR
Bolometer = device used to measure electromagnetic radiation

38. Infrared (IR) Infrared telescopes can see through interstellar dust
Ex: can see the center of Milky Way
Can be used during the day

39. Center of Milky Way: Spitzer

40. Orion Nebula in IR & Visible

41. Infrared (IR) IR observatories in space (above Earth’s atmosphere):
Spitzer Space Telescope – current IR telescope, launched in 2003

42. Spitzer and Milky Way
Photo: NASA,

43. Visible Light
White light is made up of the colors red, orange, yellow, green, blue, indigo, violet.
Remember the acronym ROY G BIV
nm wavelengths
Sir Isaac Newton discovered this 300 years ago
The color is determined by the wavelength:
Red has the longest wavelength
Violet has the shortest wavelength
Observing in visible light is called optical astronomy

44. Ultraviolet (UV) Wavelengths 400 nm down to a few nanometers
Causes sunburn and cancer
Helps produce vitamin D
Ozone protects Earth from most UV radiation, so UV studies must be done above Earth’s atmosphere

45. Ultraviolet (UV) UV telescopes:
Far Ultraviolet Explorer (FUSE) – launched in 1999
Galaxy Evolution Explorer (GALEX) – launched in 2003
Hubble Space Telescope has UV detectors

46. X-Rays Wavelengths are a few nm to hundredths of a nm
Have medical uses
Blocked by Earth’s atmosphere, so observing done from space

47. X-Rays X-Ray telescopes:
Chandra X-Ray Observatory – launched in 1999 aboard the Columbia. Still in operation
Nustar X-Ray Telescope – launched June 13, 2012 to image the sky in high energy x-rays

48. Chandra

49. W49b: Supernova: Chandra

50. Nustar

51. Gamma Rays Shortest wavelength, therefore highest energy
Associated with radioactivity
Observing done from space

52. Gamma Rays Telescopes count photons in a given direction
Photon – packet of electromagnetic radiation (i.e., particle of light)
Photons are scarce, takes hours to days to capture one photon
Fermi Space Telescope – launched June 11, 2008

53. Artists illustration of Fermi Space Telescope
Photo: /

54. Moon in Gamma: CGRO Photo: http://www.answers.com/topic/
gamma-ray?cat=health

55. The Sky in Many Wavelengths
Slide Show

56. Milky Way in Visible Light
Photo: University of Washington,
lecture/pix.html

57. Milky Way in Radio: 73 cm wavelength
Photo: Washington University,
lecture/pix.html

58. Milky Way in Radio: 21 cm wavelength
Photo: Washington University,
lecture/pix.html

59. Milky Way in Microwaves: COBE

60. Galactic Center in Radio
Photo: UC San Diego,

61. Milky Way in IR: IRAS
Photo: Caltech,

62. Photo:
astro.livjm.ac.uk/
courses/phys134/
cosmo.html

63. Sky in Ultraviolet Photo: http://minho.kasi.re.kr/iCAP/
ImageGallery/0705.AllSky.html

64. X-Ray Sky: ROSAT
Photo: APOD,

65. Gamma Ray Sky Photo: http://www.mpi-hd.mpg.de/hfm/
HESS/public/physics/allsky1_egret.gif

66. 1st Light for Fermi Gamma Ray Telescope, 8-26-08

67. Milky Way in Multiple Wavelengths