1. Astronomy 101 The Solar System Tuesday, Thursday Tom Burbine tomburbine@astro.umass.edu

2. Course Course Website: –http://blogs.umass.edu/astron101-tburbine/http://blogs.umass.edu/astron101-tburbine/ Textbook: –Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny. You also will need a calculator.

3. There is an Astronomy Help Desk that is open Monday-Thursday evenings from 7-9 pm in Hasbrouck 205. There is an open house at the Observatory every Thursday when it’s clear. Students should check the observatory website before going since the times may change as the semester progresses and the telescope may be down for repairs at times. The website is http://www.astro.umass.edu/~orchardhill/index.html. http://www.astro.umass.edu/~orchardhill/index.html

4. HWs #6, #7, and #8 Due by Feb. 23 rd at 1 pm

5. News: Water on Enceladus (moon of Saturn) The Cassini spacecraft found negatively charged water ions in the atmosphere On Earth, such ions are often seen where liquid water is in motion, such as waterfalls or crashing ocean waves. http://www.msnbc.msn.com/id/35313176/ns/technology_and_science-space /

6. Atoms make up molecules H 2 O - water CO 2 – carbon dioxide CH 4 - methane

9. Spectroscopy Spectroscopy is the study of the interaction between radiation and matter as a function of wavelength (λ). You can use spectroscopy to determine what is in a body (planet, star, etc.) or atmosphere http://upload.wikimedia.org/wikipedia/commons/f/f5/Light_dispersion_conceptual_waves.gif

10. How did scientists determined that there was water on the Moon?

11. Water on the Moon http://www.nasa.gov/images/content/388950main_ROGER_2-516.jpg White line - NASA' Cassini spacecraft Blue line - NASA's Moon Mineralogy Mapper instrument on the Indian Chandrayaan-1 spacecraft Grey - H 2 O and OH absorptions

12. Definitions Reflectance – How much light an object reflects Absorption – Light is absorbed and not reflected

13. Light cause water molecules to vibrate http://www.btinternet.com/~martin.chaplin/vibrat. htmlhttp://www.btinternet.com/~martin.chaplin/vibrat. html

14. How much water? If you had a cubic meter of lunar soil, you could squeeze it and get out a liter of water Water has to be near the surface

15. How do you use light to determine what is in an astronomical body like a star?

16. What happens when electrons absorb energy? http://www.meditech.cn/images/pic9.jpg

17. http://library.thinkquest.org/C006669/media/Chem/img/bohr.gif

18. Energy levels where an electron can reside To go to a higher energy level, an electron needs to gain energy To go to a lower energy level, an electron needs to lose energy

19. eV 1 eV = 1.6 x 10 -19 Joules

20. Rules An electron can not jump to a higher energy level unless it gains energy from somewhere else –Absorbs a photon –Gains kinetic energy from an impacting particle To go to a lower energy level, the electron must lose energy –Emits a photon Electron jumps can occur only with the particular amounts of energy representing differences between possible energy levels

22. Heated hydrogen gas Emission line spectrum White light through cool hydrogen gas Absorption line spectrum

23. Types of spectra Emission – radiation is emitted at characteristic wavelengths –Material is “hot” so electrons keep on bumping into each other and transferring kinetic energy to each other so they jump between particular energy levels Absorption – radiation is absorbed at characteristic wavelengths –Radiation passes through the material

24. http://www.astro.bas.bg/~petrov/herter00_files/lec07_04.jpg

25. So why is this important Different elements have different number of electrons Different elements have different energy levels for their electrons

26. So Different elements can absorb light at specific energies Different elements can emit light at specific energies So if you can measure the wavelength of the light from an astronomical body, you can determine whats in it

27. Emission line spectra

28. How can you determine velocities of objects? Doppler Shift – The wavelength of light changes as the source moves towards or away from you Since you know the wavelength position of emission or absorption features If the positions of the features move in wavelength position, you know the source is moving

30. So Source moving towards you, wavelength decreases –blueshift Source moving away from you, wavelength increases –redshift http://www.youtube.com/watch?v=-t63xYSgmKE http://www.youtube.com/watch?v=a3RfULw7aAY

31. nanometer 1 nanometer = 1 x 10 -9 meters

32. Blackbody A black body is an object that absorbs all electromagnetic radiation that falls onto it. Perfect emitter of radiation Radiates energy at every wavelength http://www.daviddarling.info/images/blackbody.jpg

33. Stars and planets act can be modeled as blackbodies http://www.astro.ncu.edu.tw/contents/faculty/wp_chen/Ast101/blackbody_curves.jpg

34. Stefan-Boltzman Law - The energy radiated by a blackbody per second per unit area is proportional to the fourth power of the temperature Energy emitted  T 4 s * m 2 Wien’s Law – There is an inverse relationship between the wavelength of the peak of the emission of a black body and its temperature Peak position  1/T

35. Stars and planets act can be modeled as blackbodies http://www.astro.ncu.edu.tw/contents/faculty/wp_chen/Ast101/blackbody_curves.jpg

36. Blackbody curves http://www.mhhe.com/physsci/astronomy/applets/ Blackbody/frame.htmlhttp://www.mhhe.com/physsci/astronomy/applets/ Blackbody/frame.html

37. http://www.rap.ucar.edu/general/asap-2005/Thur-AM2/Williams_DoD_Satellites_files/slide0005_image020.gif

38. http://csep10.phys.utk.edu/astr162/lect/light/radiation.html

39. Stefan Boltzman Law For the same size object (same surface area), energy emitted per second is proportional to T 4 For example if a body goes from a temperature of 1,000 to 5,000 degrees Kelvin How many times more energy is emitted per second from the hotter body? –Energy emitted per second  (5000) 4 = (5) 4 = 625 times (1000) 4

40. Power Power is in Joules/second = Watts

41. Stefan-Boltzman Law Emitted power per square meter of surface = σT 4 Temperature in Kelvin σ = 5.7 x 10 -8 Watt/(m 2 * K 4 ) For example, if the temperature of an object is 10,000 K Emitted power per square meter = 5.7 x 10 -8 x (10,000) 4 Emitted power per square meter = 5.7 x 10 -8 x (1 x 10 16 ) Emitted power per square meter = 5.7 x 10 8 W/m 2

42. Wien’s Law Wavelength of Maximum intensity of the blackbody curve peak = 2,900,000 nm T (Kelvin) λ max = 2,900,000/10,000 nm λ max = 290 nm 1 nanometer = 1 x 10 -9 meters λ max = 290 nm = 2.0 x 10 -7 meters

43. New Rings around Saturn Seen in the infrared by the Spitzer Telescope Made of dust and ice; Dust is 80 Kelvin Lies some 13 million km from the planet Tilted 27 degrees from main ring plane 50 times more distant than the other rings and in a different plane. Probably made up of debris kicked off Saturn's moon Phoebe by small impacts.

44. Why infrared for dust? Cold things give off more light in infrared than visible

46. When you observe an astronomical body You measure intensity Intensity – amount of radiation

47. When you see an object in the sky You measure its brightness Its brightness is a function of its –Distance from Earth (can be calculated from orbit) If star: -Luminosity - is the amount of energy a body radiates per unit time If planet –Albedo –Size

49. Inverse Square Law The apparent brightness varies inversely by the square of the distance (1/d 2 ) If the Earth was moved to 10 Astronomical Units away, the Sun would be 1/100 times dimmer If the Earth was moved to 100 Astronomical Units away, the Sun would be 1/10000 times dimmer

50. If the Earth was moved to 1 x 10 8 Astronomical Units away, the Sun would be … A) 1 x 10 -12 times dimmer B) 1 x 10 -14 times dimmer C) 1 x 10 -16 times dimmer D) 1 x 10 -18 times dimmer E) 1 x 10 -20 times dimmer

51. If the Earth was moved to 1 x 10 8 Astronomical Units away, the Sun would be … A) 1 x 10 -12 times dimmer B) 1 x 10 -14 times dimmer C) 1 x 10 -16 times dimmer D) 1 x 10 -18 times dimmer E) 1 x 10 -20 times dimmer

52. Luminosity-Distance Formula Apparent brightness = Luminosity 4  x (distance) 2 Usually use units of Solar Luminosity L Sun = 3.8 x 10 26 Watts

55. Magnitude System Brighter –lower number http://www.astronomynotes.com/starprop/appmag.gif 4 Vesta brightest asteroid

56. Magnitude differenceRelative intensity 01 12.51 26.31 315.8 439.8 5100 1010 4 1510 6

58. Initially Everybody observed with their eyes

59. Figure 7.1

60. Figure 7.2a Parallel lightLens

61. Figure 7.2b

62. Why are Telescopes better than your eyes? They can observe light in different wavelength regions (eyes can only see visible light) They can collect more light than eyes They can be built to compensate for the distorting effects of the atmosphere

63. Figure 7.6 Refracting telescope

64. Reflecting Telescope

65. Reflecting Telescopes

66. Resulting image inverted

67. All large modern telescopes are reflectors Since light passes through the lens of a refracting telescope, You need to make the lens from clear, high- quality glass with precisely shaped surfaces

68. It is Its easier to make a high-quality mirror than a lens

69. Also, Large lenses are extremely heavy

70. Also Lens focuses red and blue light slightly differently Called chromatic aberration http://en.wikipedia.org/wiki/File:Lens6a.svg

71. Also Light can be absorbed by the glass as it passes through the glass Minor problem for visible, but severe for ultraviolet and infrared light

72. Size of a telescope Diameter of its primary mirror or lens Light collecting area is proportional to the diameter squared since Collecting area =  r 2 E.g., 8-meter telescope

73. Telescope that took image b is twice as big as telescope that took image a Larger the telescope, more detail can be seen ab

74. Telescope on Mauna Kea (14,000 feet high) Telescope is Japanese Subaru 8-m telescope

75. Atmosphere Atmosphere can absorb light Atmosphere can scatter light Atmosphere can distort light (twinkling)

76. Twinkling Twinkling of stars is caused by moving air currents in the atmosphere. The beam of light from a star passes through many regions of moving air while on its way to an observer’s eye or telescope. Each atmospheric region distorts the light slightly for a fraction of a second.

78. Advantages of space-based telescopes It can be open 24 hours, 7 days of week Do not have to worry about distorting effects of atmosphere There is no extra background of light due to scattering of light in the Earth’s atmosphere Observe in more wavelength regions

79. Figure 7.20

80. http://www.scienzagiovane.unibo.it/English/radio-window/images/radiazioni-em.jpg

81. Infrared light absorbed by molecules http://www.ucar.edu/learn/1_3_1.htm

82. Not all light from a star reaches Earth

83. Light in space can be affected by dust http://www.ipac.caltech.edu/2mass/outreach/survey.html http://en.wikipedia.org/wiki/File:Rayleigh_sunlight_scattering.png

85. It does not help That you are closer to the stars

86. To measure light In the past, they used photographic plates Now they use CCDs (charge-coupled devices) CCD are electronic detectors CCDs are chips of silicons

87. Figure 7.5

88. CCDs CCDs convert light into electrons William Boyle George Smith Shared the 2009 Physics Nobel Prize for their discovery

89. How do they work? The CCD is made up of pixels. As the light falls on each pixel, the photons become electrons due to the photoelectric effect. The photoelectric effect happens when photons of light hit the silicon of the pixel and knock electrons out of place. These electrons are then stored. Essentially, the charge in each row is moved from one site to the next, a step at a time. This has been likened to a “bucket row” or human chain, passing buckets of water down a line. As these buckets of electrons reach the end of the line they are dumped out and measured, and this analog measurement is then turned into a digital value. Thus, a digital grid is made which describes the image.

90. Color separation for digital cameras Colored filters

91. CCDs CCDs can collect 90% of photons that strike them Photographic plates can only collect 10% of the photons CCDs are split into squares called pixels Data is in electronic form

92. Hubble Telescope Can observe in visible, infrared, and ultraviolet wavelength regions Named after Edwin Hubble, the father of modern cosmology

93. Hubble (launched in 1990) Telescope is the size of a school bus 2.4 m mirror

95. Initially Hubble’s primary mirror was polished to the wrong shape Was too flat at the edges Was barely 2.3 micrometers out from the required shape (1/50 the width of a human hair) Images were not focused as well as they could be Later shuttle mission fixed this problem by installing a number of small mirrors

96. http://dayton.hq.nasa.gov/IMAGES/SMALL/GPN-2002-000064.jpg

97. Jupiter

98. http://video.nationalgeographic.com/video/player/ science/space-sci/exploration/hubble-sci.htmlhttp://video.nationalgeographic.com/video/player/ science/space-sci/exploration/hubble-sci.html

99. Hubble replacement The first major components of the new James Webb Space Telescope are now being assembled. While Hubble is the size of a bus, the new James Webb will be the size of a jetliner. Will launch in 2014 James Webb is a former NASA administrator during the Apollo program

100. http://www.youtube.com/watch?v=SpkrVw_E6N whttp://www.youtube.com/watch?v=SpkrVw_E6N w

101. Any Questions?