Lab 11

1. Astronomy 105 Laboratory Lab 11

2. Lab Quiz 11

3. Hubble discovered that galaxies are moving away from the Milky Way with velocities that are proportional to their • size. • color. • distance. • mass.

4. Consider two galaxies which are different distances from the Milky Way. One galaxy is 10 Mly distance and the other 30 Mly. How much larger or smaller is the recessional velocity of the more distant galaxy? • 3 times larger • 6 times larger • 9 times larger • 3 times smaller • 6 times smaller • 9 times smaller

5. Consider two galaxies that are the same size but one is twice as far away as the other. The more distant galaxy will have ____ compared to the closer galaxy. • ½ the angular size • ¼ the angular size • 2 times the angular size • 4 times the angular size

6. In today’s lab you will determine the rotation rate of the planet Saturn by using • Hubble’s Law. • Newton’s Law of Gravity. • the Doppler Effect. • the luminosity-distance formula. • the distance modulus.

7. AST 105Review for Lab ExamExam Next Week!

8. Study! • About 3-5 questions from each lab exercise • Review • Main concepts covered • Procedures and measurements • Questions and calculations • Bring a scantron: 882-E • Review material – Power point slides online

9. Experimental Measurements

10. Physical quantities can never be measured with absolute precision Scientific Experiments / Observations

11. How Many Significant Figures 0.089 2 1.089 4 12000 2 12001 5

12. 10 raised to an integer power decimal number (1-9) Scientific Notation 3.502 x 106 Number Significant Figures Scientific Notation 9004 4 9.004 x 103 0.000007 1 7 x 10-6 4.3 x 101 43 2 7,805,000,000 4 7.805 x 109 0.0408 3 4.08 x 10-2 8.4 2 8.4 x 100

13. To multiply two numbers in scientific notation multiply the decimal parts of the numbers and add the exponents algebraically. (4.0 x 104)(2.0 x 103) = (4.0 x 2.0)(104 x 103) = (8.0) x (104+3) = 8.0 x 107 (6.0 x 102)(2.0 x 105) = 12.0 x 107 = 1.2 x 108

14. Constellations – Sky Familiarization

15. Summer Solstice Ecliptic Sun’s Path Vernal Equinox Celestial Equator Autumnal Equinox North East South

16. Zenith West Horizon March 7 @ 8:00 p.m North 32° X East South Meridian

17. March 7 @ 8:00 p.m East Horizon West Horizon not visible East West Meridian

18. Sky Familiarization • A Few More Things to Remember • Any vertical line on your SC-1 (north-south) is a meridian. • Approximately one half of the stars on the SC-1 are visible at any given time (12 hours of RA). • Meridian moves eastward 4 minutes each day (Earth’s revolution) • Meridian moves eastward 1 hour of RA for every hour of time (Earth’s rotation)

19. The Moon

20. N.P. N.P. N.P. N.P. Synchronous Rotation EARTH N.P. Does the Moon rotate on it’s axis? What is the Moon’s hidden side? MOON

21. Sunset Sunset Midnight Midnight Noon Noon N.P. N.P. Sunrise Sunrise N.P. 1st quarter Phase: Rise Time: Noon Set Time: Midnight Transit: Sunset

22. Mercury’s Orbit

24. Verifying Kepler’s 1st Mercury’s Orbit Major Axis F F Equal Time Intervals

25. Name (print):__________________________________ Section: _____ SUN 6 10 km 0 10 20 30 40 50 60 70 80 90 100 110 120 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 AU Verifying Kepler’s 2nd Equal area in equal time. Mercury’s Orbit Major Axis

26. Kepler’s 3rd P2=ka3 Finding the Sun’s mass.

27. Emission Spectra

29. Formation of Emission and Dark Line Spectra

32. The Earth’s Orbital Velocity

33. 1 The Doppler Effect 2 3 4 5 Velocity = 0 Increasing Velocity Increasing Velocity

34. VA ? ? VB  o Arcturus • From measured Doppler Shift • Orbital velocity of Earth • Radial velocity of Arcturus • Radius of the Earth’s Orbit

35. The HR Diagram

36. Apparent Brightness of Stars • Stellar Luminosity -- Total amount of light energy emitted each second • Surface Area • Temperature • Distance from the Earth

37. Magnitude • Stellar Brightness • Apparent Magnitude (mv) - Brightness from Earth • Absolute Magnitude (Mv) - Brightness from 10 pc Absolute magnitude depends only on a star’s luminosity (the star’s wattage)

38. Spectral Classification B

39. HR Diagram -10 -5 0 +5 +10 +15 The Sun M=+5 G2 Absolute Magnitude O B A F G K M Temperature

40. The Sun’s Spectral and Luminosity Class: G2 V

41. Which star appears faintest in our sky? Regulus Which star has the greatest luminosity? Antares Which star has the highest surface temperature? Spica Which star is a red giant? Aldebaran Which main-sequence star has the longest lifetime? Alpha Centauri

42. The Distance to the Pleiades

43. Stars in a Cluster • Common Properties • Distance • Age • Different Properties • Spectral Types (temperature) • Luminosity Class (size)

44. HR Diagram Absolute Magnitude Main-sequence O B A F G K M -0.4 color index 1.3 d >10 pc { DM d <10 pc Apparent Magnitude -0.4 color index 1.3 Star Cluster 10 pc Distance Modulus = m - M The difference between the absolute magnitude and the apparent magnitude can be used to find the distance to a star cluster. If m-M > 0 then the distance to the cluster is > 10 pc. If m-M = 0 then the distance to the cluster is = 10 pc. If m-M < 0 then the distance to the cluster is < 10 pc. Color-Magnitude Diagram d <10 pc 10 pc d >10 pc

45. √4 = 2 Cluster A: Distance 50 ly Cluster B: Distance ? The apparent brightness of the stars in Cluster B are 4 times fainter than the stars in Cluster A. What is the distance to Cluster B? Inverse-Square Law: Cluster B is 2 times farther or 100 ly.

46. Ages and Distances to Clusters

47. Interstellar Dust • Reddens Light (makes stars appear cooler) • Dims Light (makes stars appear further away)

48. Pleiades - Open Cluster Distance - 380 ly Age - 60 million years B6 stars -- 60 million yrs. MS lifetime age of cluster = lifetime of stars at main-sequence turnoff point

49. Hubble’s Lab

50. 10 Mpc 20 Mpc 30 Mpc 40 Mpc Milky Way A C B 1400 2800 700 V = 0 700 1400 2100 km/sec Alien’s Galaxy 40 Mpc 30 Mpc 20 Mpc 10 Mpc 10 Mpc 20 Mpc Milky Way A C B 2800 1400 2100 700 V = 0 700 1400 km/sec Recessional Velocity is Proportional to Distance The Universe is Expanding!!