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

1. Astronomy 101The Solar SystemTuesday, ThursdayTom Burbinetomburbine@astro.umass.edu

2. Course • Course Website: • 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.

4. HWs #6, #7, #8, and #9 • Due by Feb. 23rd at 1 pm

5. Exam #2 • February 25th • 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/player.php?videoRef=sun_storm

8. Solar Constant • Energy received at Earth’s distance from the Sun • ~1400 W/m2 • 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

14. 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 = mc2 • 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. 0.993 kg 1 kg 1 kg 0.993 kg 0.007 kg http://observe.arc.nasa.gov/nasa/exhibits/stars/star_6.html

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 ~1038 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. Density Temperature

38. Parts of SunCore • 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