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Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20 Tom Burbine tomburbine@astro.umass.edu. Course. Course Website: http://blogs.umass.edu/astron101-tburbine/ Textbook: Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny .

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  1. Astronomy 101The Solar SystemTuesday, Thursday2:30-3:45 pmHasbrouck 20Tom 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. Office Hours • Mine • Tuesday, Thursday - 1:15-2:15pm • Lederle Graduate Research Tower C 632 • Neil • Tuesday, Thursday - 11 am-noon • Lederle Graduate Research Tower B 619-O

  4. Homework • We will use Spark • https://spark.oit.umass.edu/webct/logonDisplay.dowebct • Homework will be due approximately twice a week

  5. Astronomy Information • Astronomy Help Desk • Mon-Thurs 7-9pm • Hasbrouck 205 • The Observatory should be open on clear Thursdays • Students should check the observatory website at: http://www.astro.umass.edu/~orchardhill for updated information • There's a map to the observatory on the website.

  6. Final • Monday - 12/14 • 4:00 pm • Hasbrouck 20

  7. No class this Tuesday • Space Station Bound: A Day in the Life of a Scientist Astronaut with Cady Coleman '91PhD • Tuesday, October 13, 2009 • 4:00 pm • Engineering Lab II • Room 119 • Free Admission

  8. HW #5 (replace) • Due Today

  9. HW #7 • Due next Thursday

  10. HW #8 • Due next Thursday

  11. October 9 (Tomorrow): 7:30 AM • LCROSS (Lunar Crater Observation and Sensing Satellite) • LCROSS’ spent Upper-Stage Centaur Rocket will crash into the Moon;s South Pole • LCROSS will then follow into the Moon • Looking for water • http://www.youtube.com/watch?v=NQ8d2Oacv2M

  12. 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.

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

  14. 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

  15. Stefan-Boltzman Law - energy radiated per unit surface area of a black body in unit time is directly proportional to the fourth power of the black body’s temperature • Wien’s Law - blackbody curve at any temperature has essentially the same shape as the curve at any other temperature, except that each wavelength is displaced, or moved over, on the graph

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

  17. Blackbody curves • http://www.mhhe.com/physsci/astronomy/applets/Blackbody/frame.html

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

  19. Power • Power is in Joules/second = Watts

  20. Stefan-Boltzman Law • Emitted power per square meter of surface = σT4 • Temperature in Kelvin • σ = 5.7 x 10-8 Watt/(m2*K4) • 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 1016) • Emitted power per square meter = 5.7 x 108 W/m2

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

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

  23. 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

  24. Inverse Square Law • The apparent brightness varies inversely by the square of the distance (1/d2) • 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

  25. If the Earth was moved to 1 x 108 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

  26. If the Earth was moved to 1 x 108 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

  27. Luminosity-Distance Formula • Apparent brightness = Luminosity 4 x (distance)2 Usually use units of Solar Luminosity LSun = 3.8 x 1026 Watts

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

  29. Initially • Everybody observed with their eyes

  30. Figure 7.1

  31. Parallel light Lens Figure 7.2a

  32. Figure 7.2b

  33. 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

  34. Refracting telescope Figure 7.6

  35. Reflecting Telescope

  36. Reflecting Telescopes

  37. Resulting image inverted

  38. 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

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

  40. Also, • Large lenses are extremely heavy

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

  42. 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

  43. Size of a telescope • Diameter of its primary mirror or lens • Light collecting area is proportional to the diameter squared since • Collecting area =  r2 • E.g., 8-meter telescope

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

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