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, #8, and #9 Due by Feb. 23 rd at 1 pm

5. Exam #2 February 25 th Covers from last exam up to today

6. Sun Brightest star in the sky Closest star to Earth Next Closest is Alpha Centauri, which is 4.3 light years away

7. Sun video http://www.space.com/common/media/video/play er.php?videoRef=sun_stormhttp://www.space.com/common/media/video/play er.php?videoRef=sun_storm

8. Solar Constant Energy received at Earth’s distance from the Sun ~1400 W/m 2 50-70 % reaches Earth’s surface 30% absorbed by atmosphere 0-20% reflected away by clouds

9. http://en.wikipedia.org/wiki/File:Sun_Life.png

11. Absorption lines

12. Energy Source for Sun Fusing hydrogen into helium –Hydrogen nucleus – 1 proton –Helium nucleus – 2 protons, 2 neutrons Need high temperatures for this to occur ~10 to 14 million degrees Kelvin

13. http://www.astronomynotes.com/starsun/s3.htm

16. How does Fusion Convert Mass to Energy What is the most famous formula in the world?

17. E = mc 2 m is mass in kilograms c is speed of light in meters/s E (energy) is in joules very small amounts of mass may be converted into a very large amount of energy

18. Law Law of Conservation of mass and energy –Sum of all mass and energy (converted into the same units) must always remain constant during any physical process

19. http://observe.arc.nasa.gov/nasa/exhibits/stars/star_6.html 1 kg 0.993 kg 1 kg 0.993 kg 0.007 kg

20. Reaction 4 protons → helium-4 + 2 neutrinos + energy Neutrino-virtually massless, chargeless particles Positron-positively charged electron – annihilated immediately by colliding with an electron to produce energy

21. Antiparticles Antiparticle – particle with the same mass and opposite electric charge Antiparticles make up antimatter Annihilation – when a particle and an antiparticle collide Antimatter is said to be the most costly substance in existence, with an estimated cost of $62.5 trillion per milligram.

22. Fusion reaction Much more complicated than 4 protons → helium-4 + 2 neutrinos + energy

24. Deuteron – Deuterium (hydrogen with a neutron) nucleus

25. Proton-Proton Chain Reaction This reaction occurs ~10 38 times each second It if occurred faster, Sun would run out of fuel

26. Neutrinos Neutrinos – almost massless particles No charge It takes a neutrino about 2 seconds to exit the Sun The neutrino was first postulated in 1930 by Wolfgang Pauli to preserve conservation of energy, conservation of momentum, and conservation of angular momentum during the decay of a neutron into a proton where an electron is emitted (and an antineutrino). Pauli theorized that an undetected particle was carrying away the observed difference between the energy, momentum, and angular momentum of the initial and final particles.

27. How was the Homestake Gold Mine used to detect neutrinos? A 400,000 liter vat of chlorine-containing cleaning fluid was placed in the Homestake gold mine Every so often Chlorine would capture a neutrino and turn into radioactive argon Modelers predict 1 reaction per day Experiments found 1 reaction every 3 days Newer detectors used water to look for reactions

28. What was the solar neutrino problem? Less neutrinos appeared to have been produced from the Sun than expected from models

29. Solution of Problem Neutrinos come in three types (slightly different masses) –Electron neutrino –Muon neutrino –Tau Neutrino Experiment could only detect electron neutrinos Fusion reactions in Sun only produced electron neutrinos Electron neutrinos could change into other types of neutrinos that could not be detected Neutrino oscillations – one type of neutrino could change into another type

30. Fusion The rate of nuclear fusion is a function of temperature Hotter temperature – higher fusion rate Lower temperature – lower fusion rate If the Sun gets hotter or colder, it may not be good for life on Earth

31. What is happening to the amount of Helium in the Sun? A) Its increasing B) its decreasing C) Its staying the same

32. What is happening to the amount of Helium in the Sun? A) Its increasing B) its decreasing C) Its staying the same

33. So how does the Sun stay relatively constant in Luminosity (power output)

34. http://www-ssg.sr.unh.edu/406/Review/rev8.html

35. Figure 15.8

36. Figure 15.4

37. Temperature Density

38. Parts of Sun Core Core – 15 million Kelvin – where fusion occurs

39. Figure 15.4

40. Radiation zone Radiation zone – region where energy is transported primarily by radiative diffusion Radiative diffusion is the slow, outward migration of photons

41. Figure 15.13

42. Photons emitted from Fusion reactions Photons are originally gamma rays Tend to lose energy as they bounce around Photons emitted by surface tend to be visible photons Takes about a million years for the energy produced by fusion to reach the surface

43. Figure 15.4

44. Convection Zone Temperature is about 2 million Kelvin Photons tend to be absorbed by the solar plasma Plasma is a gas of ions and electrons Hotter plasma tends to rise Cooler plasma tends to sink

45. Figure 15.14

46. Granulation – bubbling pattern due to convection bright – hot gas, dark – cool gas Figure 15.14

48. Figure 15.10

49. Figure 15.4

50. Classification of Stars Stars are classified according to luminosity and surface temperature Luminosity is the amount of power it radiates into space Surface temperature is the temperature of the surface

51. Stars have different colors

53. Surface Temperature Determine surface temperature by determining the wavelength where a star emits the maximum amount of radiation Surface temperature does not vary according to distance so easier to measure

55. 1913

56. Who were these people? These were the women (called computers) who recorded, classified, and catalogued stellar spectra Were paid 25 cents a day Willamina Fleming (1857-1911) classified stellar spectra according to the strength of their hydrogen lines Classified over 10,000 stars

57. Fleming’s classification A - strongest hydrogen emission lines B - slighter weaker emission lines C, D, E, … L, M, N O - weakest hydrogen lines emission lines

58. Annie Jump Cannon (1863-1941) Cannon reordered the classification sequence by temperature and tossed out most of the classes She devised OBAFGKM

59. More information Each spectral type had 10 subclasses e.g., A0, A1, A2, … A9 in the order from the hottest to the coolest Cannon classified over 400,000 stars

60. OBAFGKM Oh Be A Fine Girl/Gal Kiss Me http://www.mtholyoke.edu/courses/tburbine/ASTR223/O BAFGKM.mp3http://www.mtholyoke.edu/courses/tburbine/ASTR223/O BAFGKM.mp3

62. http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap04/FG04_05.jpg

63. http://spiff.rit.edu/classes/phys301/lectures/spec_lines/spec_lines.html

64. http://scope.pari.edu/images/stellarspectrum.jpg

65. But absorption line - A dark feature in the spectrum of a star, formed by cooler gas in the star's outer layers (the photosphere) that absorbs radiation emitted by hotter gas below.

68. Cecilia Payne-Gaposchkin (1900-1979) Payne argued that the great variation in stellar absorption lines was due to differing amounts of ionization (due to differing temperatures), not different abundances of elements

69. Cecilia Payne-Gaposchkin (1900-1979) She proposed that most stars were made up of Hydrogen and Helium Her 1925 PhD Harvard thesis on these topics was voted best Astronomy thesis of the 20 th century

73. It takes progressively more energy to remove successive electrons from an atom. That is, it is much harder to ionize electrons of He II than He I.

75. Hertzsprung-Russell Diagram Both plotted spectral type (temperature) versus stellar luminosity Saw trends in the plots Did not plot randomly

77. Remember Temperature on x-axis (vertical) does from higher to lower temperature O – hottest M - coldest

78. Most stars fall along the main sequence Stars at the top above the main sequence are called Supergiants Stars between the Supergiants and main sequence are called Giants Stars below the Main Sequence are called White Dwarfs Hertzsprung-Russell Diagram

79. wd white dwarfs

80. giant – a star with a radius between 10 and 100 times that of the Sun dwarf – any star with a radius comparable to, or smaller than, that of the Sun

81. Classifications Sun is a G2 V Betelgeuse is a M2 I

83. Radius Smallest stars on the main sequence fall on the bottom right Largest stars on main sequence fall on the top left At the same size, hotter stars are more luminous than cooler ones At the same temperature, larger stars are more luminous than smaller ones

85. Main Sequence Stars Fuse Hydrogen into Helium for energy On main sequence, mass tends to decrease with decreasing temperature

87. What does this tell us The star’s mass is directionally proportional to how luminous it is More massive, the star must have a higher nuclear burning rate to maintain gravitational equilibrium So more energy is produced

89. Main Sequence Lifetimes The more massive a star on the main sequence, the shorter its lifetime More massive stars do contain more hydrogen than smaller stars However, the more massive stars have higher luminosities so they are using up their fuel at a much quicker rate than smaller stars

91. Ages Universe is thought to be about 14 billion years old So less massive stars have lifetimes longer than the age of the universe More massive stars have ages much younger So stars must be continually forming

93. Things to remember 90% of classified stars are on main sequence Main sequence stars are “young” stars If a star is leaving the main sequence, it is at the end of its lifespan of burning hydrogen into helium

94. Remember Largest stars on main sequence are O stars Largest stars that can exist are supergiants

95. You need to know stellar classifications O, B, A, F, G, K, M A0, A1, A2, … A9 in the order from the hottest to the coolest

96. wd white dwarfs

97. Classifications Sun is a G2 V Betelgeuse is a M2 I Vega is a A0 V Sirius is a A1 V Arcturus is a K3 III

98. Any Questions?