NYU Observational astronomy 2013-2014

Lecture 3:
-gravity
-the Moon
-other solar system moons

Transcript

1. lecture 3 gravity, our moon - other moons observational astronomy 1
2. lecture 3 gravity, our moon - other moons recap •the earth spins on its axis •the earth revolves around the sun 2
3. lecture 3 gravity, our moon - other moons recap •the earth spins on its axis • this causes the changes seen through the night in the skyscape • the alternation of day and night •the earth revolves around the sun • this causes the seasonal changes in the night sky • the alternation of seasons 3
4. lecture 3 gravity, our moon - other moons recap •the earth spins on its axis • this causes the changes seen through the night in the skyscape • the alternation of day and night •the earth revolves around the sun • this causes the seasonal changes in the night sky • the alternation of seasons 4
5. lecture 3 gravity, our moon - other moons recap the solar day lasts 24h. time passing between two transits of the Sun the sidereal day is 23h 56m. time passing between two transits of the same (distant) celestial body 5
6. lecture 3 gravity, our moon - other moons equator NP SUN winter solstice summer solstice the axial tilt of the earth is 23.4 degrees. the misalignment of earth’s spin axis and ecliptic plane cause the season changes because of the different length of the day and angle of incidence of the solar radiation 6
7. lecture 3 gravity, our moon - other moons equator NP SUN winter solstice summer solstice the axial tilt of the earth is 23.4 degrees. the misalignment of earth’s spin axis and ecliptic plane cause the season changes because of the different length of the day and angle of incidence of the solar radiation 7
8. lecture 3 gravity, our moon - other moons equator NP SUN winter solstice summer solstice the axial tilt of the earth is 23.4 degrees. the misalignment of earth’s spin axis and ecliptic plane cause the season changes because of the different length of the day and angle of incidence of the solar radiation A B C 8
9. lecture 3 gravity, our moon - other moons equator tropic of cancer tropic of capricorn antarctic circle arctic circle the declination of the sun at noon changes through the year, with maximum and minimum at 23.4 degrees. SUN 9
10. lecture 3 gravity, our moon - other moons equator tropic of cancer tropic of capricorn antarctic circle arctic circle SUN what is the declination of the sun? Dec -90d 90d 24h 0h RA 10
11. lecture 3 gravity, our moon - other moons •the earth’s moon •other solar system moons 11
12. lecture 3 gravity, our moon - other moons •concepts of classical gravity •the earth’s moon •other solar system moons 12
13. lecture 3 gravity, our moon - other moons Empirically describe the motion of celestial bodies in the heliocentric system kepler’s laws 13
14. lecture 3 gravity, our moon - other moons kepler’s laws Empirically describe the motion of celestial bodies in the heliocentric system 1.The orbit of every planet is an ellipse with the Sun at one of the two foci. 2.A line joining a planet and the Sun sweeps out equal areas during equal intervals of time. 3.The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit. 14
15. lecture 3 gravity, our moon - other moons concepts of classical gravity 15
16. lecture 3 gravity, our moon - other moons 16
17. lecture 3 gravity, our moon - other moons 17
18. lecture 3 gravity, our moon - other moons one force: gravity 18
19. lecture 3 gravity, our moon - other moons one force: gravity 19
20. lecture 3 gravity, our moon - other moons one force: gravity lecture 3 20
21. lecture 3 gravity, our moon - other moons one force: gravity lecture 3 21
22. lecture 3 gravity, our moon - other moons one force: gravity 22
23. lecture 3 gravity, our moon - other moons 23
24. lecture 3 gravity, our moon - other moons center of mass 24
25. lecture 3 gravity, our moon - other moons center of mass 25
26. lecture 3 gravity, our moon - other moons center of mass 26
27. lecture 3 gravity, our moon - other moons center of mass 27
28. lecture 3 gravity, our moon - other moons center of mass 28
29. lecture 3 gravity, our moon - other moons center of mass 29
30. lecture 3 gravity, our moon - other moons center of mass 30
31. lecture 3 gravity, our moon - other moons center of mass 31
32. lecture 3 gravity, our moon - other moons center of mass 32
33. lecture 3 gravity, our moon - other moons newton’s laws Explain the motion of celestial bodies in terms of forces 1. A body in motion tends to maintain its motion 2. 3. 33
34. lecture 3 gravity, our moon - other moons orbital elements planets orbit around sun in an ellipse (first Kepler law) 34
35. lecture 3 gravity, our moon - other moons orbital elements ellipse: locus of points equidistant from two points called foci (plural of focus) 35
36. lecture 3 gravity, our moon - other moons orbital elements ellipse: locus of points equidistant from two points called foci (plural of focus) 36
37. lecture 3 gravity, our moon - other moons orbital elements ellipse: locus of points equidistant from two points called foci (plural of focus) a1 b1 37
38. lecture 3 gravity, our moon - other moons orbital elements ellipse: locus of points equidistant from two points called foci (plural of focus) a1 b1 a2 b2 a1+b1 = a2+b2 38
39. lecture 3 gravity, our moon - other moons orbital elements ellipse: locus of points equidistant from two points called foci (plural of focus) a1 b1 a2 b2 a3 b3 a1+b1 = a2+b2 = a3+b3 39
40. lecture 3 gravity, our moon - other moons orbital elements semimajor axis semiminor axis 40
41. lecture 3 gravity, our moon - other moons orbital elements semimajor axis semiminor axis eccentricity 41
42. lecture 3 gravity, our moon - other moons orbital elements semimajor axis semiminor axis eccentricity apo-center peri-center 42
43. lecture 3 gravity, our moon - other moons semimajor axis semiminor axis eccentricity apo-center peri-center 43
44. lecture 3 gravity, our moon - other moons semimajor axis semiminor axis eccentricity apo-center peri-center inclination 44
45. lecture 3 gravity, our moon - other moons kepler’s laws Empirically describe the motion of celestial bodies in the heliocentric system 1.The orbit of every planet is an ellipse with the Sun at one of the two foci. 2.A line joining a planet and the Sun sweeps out equal areas during equal intervals of time. 3.The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit. 45
46. lecture 3 gravity, our moon - other moons the earth’s moon 46
47. lecture 3 gravity, our moon - other moons perigee (363,000 km) apogee (406,000 km) Moon’s orbit is significantly elliptical 47
48. lecture 3 gravity, our moon - other moons perigee (363,000 km) apogee (406,000 km) Moon’s orbit is significantly elliptical 48
49. Moon phases 49
50. Moon phases 50
51. Moon phases 51
52. new full first quarter third quarter waning crescent waxing crescent Moon phases waxing gibbous waning gibbous 52
53. lecture 3 gravity, our moon - other moons Moon phases 53
54. lecture 3 gravity, our moon - other moons 5o Moon phases 54
55. lecture 3 gravity, our moon - other moons orbital period = 27.3 d synodic period = 29.5 d 55
56. Moon phases 56
57. maria 57
58. highlands (terrae) 58
59. Tycho Copernicus 59
60. Tycho Copernicus 60
61. lecture 3 gravity, our moon - other moons tidal locking 61
62. lecture 3 gravity, our moon - other moons 62
63. lecture 3 gravity, our moon - other moons 1.libration in longitude uniform rotation, but elliptical orbit (exaggerated so you can see it) 63
64. lecture 3 gravity, our moon - other moons 2.libration in latitude misalignment of Moon’s axis of spin and rotation 1.libration in longitude 64
65. lecture 3 gravity, our moon - other moons 3.diurnal libration parallax change during day (highly exaggerated; actual amount is typically 8000 km / 400,000 km = 1/50 rad ~ 1 deg) 2.libration in latitude 1.libration in longitude 65
66. lecture 3 gravity, our moon - other moons 59% of the surface of the moon is visible to earth 66
67. lecture 3 gravity, our moon - other moons 67
68. lecture 3 gravity, our moon - other moons timeline 4.6 4.4 surface cools and hardens 4.2 3.9 heavy bombardment 3.8 billion years volcanism 3 ... geological quiescence 68
69. lecture 3 gravity, our moon - other moons timeline 4.6 4.4 surface cools and hardens 4.2 3.9 heavy bombardment 3.8 billion years volcanism 3 ... geological quiescence 1968 men on the moon 69
70. lecture 3 gravity, our moon - other moons 70
71. lecture 3 gravity, our moon - other moons APOLLO lunar laser ranging experiment 71
72. lecture 3 gravity, our moon - other moons APOLLO collecting rocks from the moon 72
73. lecture 3 gravity, our moon - other moons APOLLO collecting rocks from the moon mare Basalts: 3.9 billion years highland Anorthosite: 4.6 billion years Breccias and Lunar Solis from impacts 73
74. lecture 3 gravity, our moon - other moons science, 2012 74
75. lecture 3 gravity, our moon - other moons timeline 4.6 4.4 surface cools and hardens 4.2 3.9 late heavy bombardment 3.8 billion years volcanism 3 ... geological quiescence 1968 men on the moon 75
76. lecture 3 gravity, our moon - other moons 76
77. lecture 3 gravity, our moon - other moons moons of jupiter 77
78. lecture 3 gravity, our moon - other moons moons of jupiter 78
79. lecture 3 gravity, our moon - other moons moons of jupiter Io Europa Ganymede Callisto 79
80. lecture 3 gravity, our moon - other moons moons of jupiter Io Europa Ganymede Callisto 80
81. lecture 3 gravity, our moon - other moons moons of jupiter 81
82. lecture 3 gravity, our moon - other moons moons of saturn 82
83. lecture 3 gravity, our moon - other moons moon formation in situ 83
84. lecture 3 gravity, our moon - other moons moon formation in situ impactor capture 84
85. lecture 3 gravity, our moon - other moons capture 85
86. lecture 3 gravity, our moon - other moons 86
87. lecture 3 gravity, our moon - other moons 87
88. lecture 3 gravity, our moon - other moons 88
89. lecture 3 gravity, our moon - other moons 89
90. lecture 3 gravity, our moon - other moons summary 1. Kepler’s laws describe the motion of the solar system objects 2. Newton’s law explain the motion of the solar system objects in terms of one force: Gravity 3. Bodies in orbit are permanently free falling 4. Celestial orbits can be described as ellipses with eccentricity, semimajor & semiminor axis (peri- & apo-center), inclination... 5. The moon orbits the earth, synchronously (tidal locking) 6. The moon formed from the impact of a celestial body with the earth from earth material, 4.6 billion years ago. 8. A variety of moons exist in the Solar System, formed through impacts, in situ, or by capture 90
91. lecture 3 gravity, our moon - other moons reading Kaler Chapter 6.2, 9 first half, Chapter 12.1 first half Monday labs: the first outdoors lab -we may go out this week! Wednesday labs: the second outdoors lab - we learn how to use telescopes! The second indoors lab is Starry Night The third indoors lab is the Ecliptic 91