Astronomy 100 Tuesday, Thursday 2:30 - 3:45 pm Tom Burbine [email protected] www.xanga.com/astronomy100Help DeskOWL HWBy ThursdayTestTest RoomsConstants (given on top of test)FormulasYou should be acquainted withThings you definitely should knowThings you be acquainted withPercentagesHints for studyingHints for taking TestReview SessionIs everybody okay?TelescopesInitiallyWhy are Telescopes better than your eyes?Why are reflecting telescopes used more in astronomy?It isAlso,Size of a telescopeTo measure lightCCDsAtmosphereTwinklingAdvantages of space-based telescopesIt does not helpHubble TelescopeHubbleJupiterVideoAttendance PRSQuestions?Astronomy 100Tuesday, Thursday 2:30 - 3:45 pmTom [email protected]/astronomy100Help Desk• There is an Astronomy Help Desk in HAS 205.• It will be open from Monday through Thursday from 7-9 pm.OWL HW• Due Tuesday at March 8thby 11:59 pmBy Thursday• I will put on OWL everybody’s HW and PRS scores so farTest• Thursday March 10th• 40 questions• Will cover Chapters 4, 5, 6, and 7• Will not cover Supplemental chapters 2 and 3• If there is a problem with taking the test on March 10th, I need to know today• I will give you all constants you need to know• But you need to memorize formulas• Bring pencilTest Rooms• People who last names begin with A and B will be in Hasbrouck 137• Everybody else will be in Hasbrouck 20Constants (given on top of test)• c = 3 x 108m/s• G = 6.67 x 10-11 m3/(kg s2)• h = 6.626 x 10-34joule second• g = 9.8 m/s2Formulas• E = mc2• KE = ½ mv2• c = frequency * wavelength• E = h*frequency• F = mass * acceleration• Angular momentum = m * v * r• F = G M1M2distance2You should be acquainted with• Escape velocity = square root (2GMplanet/Rplanet)• Stefan-Boltzman Law• Emitted power per square meter = σ T4• σ = 5.7 x 10-8Watt/(m2Kelvin4)•Wien’sLaw• Wavelength (maximum intensity) = 2,900,000 nmT (Kelvin)Figure 6.13Figure 6.6Things you definitely should know• Doppler Shift• Calculating energy•Tides• Newton’s 3 Laws• Temperature conversion from Kelvin to Celsius• Atomic Mass, Atomic Number• What is in the nucleus• Energy Levels and the transitionsThings you be acquainted with• Periodic Table• How energy, frequency, and wavelength are related• gravitational acceleration• General information on telescopes and observingPercentages• 100% = 1.0• 10% = 0.1• 1% = .01• 0.1% = 0.001Hints for studying• Go over my notes• Go over all figures I showed in class• Make sure you can use the formulasHints for taking Test• Read the whole question carefully• Read all the answers• Check your math• Do calculations by hand and by using calculatorReview Session• I will have a review session on Wednesday March 9 from 7-9 PM in Goessmann Laboratory room 20.Is everybody okay?Telescopes• Why do we use telescopes?Initially• Everybody observed with their eyesFigure 7.1Figure 7.2aParallel light LensFigure 7.2bWhy 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 atmosphereFigure 7.6Refracting telescopeFigure 7.7Reflecting TelescopeReflecting TelescopesFigure 7.8Why are reflecting telescopes used more in astronomy?• Since light passes through the lens of a refracting telescope,• You need to make the lens from clear, high-quality glass with precisely shaped surfacesIt is• Its easier to make a high-quality mirror than a lensAlso,• Large lenses are extremely heavySize of a telescope• Diameter of its primary mirror or lens• Light collecting area is proportional to the diameter squared since• Collecting area = π r2• E.g., 8-meter telescopeTo measure light• In the past, they used photographic plates• Now they use CCDs (charge-coupled devices)• CCD are electronic detectors• CCDs are chips of siliconsFigure 7.5CCDs• 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 formAtmosphere• Atmosphere can absorb light• Atmosphere can scatter light• Atmosphere can distort light (twinkling)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.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 regionsFigure 7.20It does not help• That you are closer to the starsHubble Telescope• Can observe in visible, infrared, and ultraviolet wavelength regionsHubbleFigure 7.19bTelescope is the size of a school busJupiterVideoAttendance