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The Earth – Moon System

The Solar System. The Earth – Moon System. Martin Crow Crayford Manor House Astronomical Society. The Solar System : Earth Moon system. Last time:. The formation of the Sun (and Solar system). About the Sun. The Sun’s effect on the Earth.

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The Earth – Moon System

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  1. The Solar System The Earth – Moon System Martin Crow Crayford Manor House Astronomical Society

  2. The Solar System : • Earth Moon system Last time: The formation of the Sun (and Solar system). About the Sun The Sun’s effect on the Earth. Martin Crow Crayford Manor House Astronomical Society

  3. The Solar System : • Earth Moon system This week: The formation of the Earth and Moon Consequences of a gravitationally bound system. The local gravitational environment Phases of the Moon and its orbital characteristics. Solar and Lunar eclipses. Martin Crow Crayford Manor House Astronomical Society

  4. Some Physical data Earth Mean Earth Sun distance = 149.6 x 10⁶ km (1 A.U.) Inclination to the Sun’s equator = 7.16° Axial tilt = 23° 26’ 21” Albedo = 0.3 (Bond) Mean diameter = 12,742 km Mass = 5.97 x 10²⁴ kg Mean density = 5.52 x 10³ kg/m³ (water = 1 x 10³ kg/m³) Martin Crow Crayford Manor House Astronomical Society

  5. Moon Mean Earth Moon distance = 384.4 x 10³ km Sidereal month = 27.321582 days (27 d 7 h 43.1 min) relative to fixed frame of reference. Draconic month = 27.2122 days (the nodes precess over a period of 18.6 years) Synodic period = 29.530589 d (29 d 12 h 44 min 2.9 s) New Moon to new Moon and is commonly called a Lunar month. Anomalistic month = 27.5546 days (the line of Apsides connecting Perigee and Apogee precesses over a period of 8.85 years. Albedo = 0.12 (Bond) Mean diameter = 3,474 km Mass = 7.35 × 1022 kg  Mean density = 3.35 x 10³ kg/m³ Martin Crow Crayford Manor House Astronomical Society

  6. Formation of the Earth – Moon system The Earth formed 4.567 x 10⁹ years ago from the disk of material orbiting the newly forming Sun. Martin Crow Crayford Manor House Astronomical Society

  7. The Moon is now thought to have formed during an impact with a Mars sized object the so called ‘giant impact hypothesis’. This would have been within the first 50 x 10⁶ years of the formation of the solar system. Martin Crow Crayford Manor House Astronomical Society

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  9. Computer simulations are consistent with observations such as: The measured angular momentum of the Earth- Moon system. The small size of the Moon’s core. The composition of the Moon. Martin Crow Crayford Manor House Astronomical Society

  10. Initial Accretion of the Moon, probably from debris launched into Earth orbit by a mega-impact. B. In the last stages of accretion, so much heat accumulates that the outermost 100 km of the lunar crust melts to form a magma ocean. C. Late impacts excavate giant basins. D. Mare Nectaris and other basins form. E. Mare Imbrium forms. F. Mare Orientale forms G. Mare basalts erupt and flood many of the impact basins. H. Since 3000 Ma, only a few large rayed craters like Tycho and Copernicus have formed. Martin Crow Crayford Manor House Astronomical Society

  11. The Lunar surface Far side Near side Martin Crow Crayford Manor House Astronomical Society

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  15. Structure Earth Moon Martin Crow Crayford Manor House Astronomical Society

  16. Life on Earth Martin Crow Crayford Manor House Astronomical Society

  17. Consequences of a gravitationally bound system. Due to tidal drag the Moon’s rotation has become locked into its rotation around the Earth. The effect of this is that the Moon rotates only once for every orbit. Which is why we only see one face. The Moon raises tides on Earth with the effect that the Earth spin is slowed. This loss of energy is transferred to the Moon thereby increasing its speed. This causes the Moon to move away from the Earth by 38mm every year. Although the Earth’s spin rate reduces by only 2.3 ms per year (not constant over time and depends on the configuration of the continents) this adds up over time. During the Devonian period 400 x 10⁶ years ago the year was 400 days long with each day approx. 21.9 hrs. Martin Crow Crayford Manor House Astronomical Society

  18. The local gravitational environment. The Lagrangian points. Martin Crow Crayford Manor House Astronomical Society

  19. The Phases of the Moon Syzygy – When the Earth, Moon and Sun are aligned. Quadrature – When the Moon’s elongation is either 90° or 180° Orbital period = 27.321582 days Synodic period = 29.530589 d Martin Crow Crayford Manor House Astronomical Society

  20. The Moons orbit The Moons orbit is an ellipse. The Moons orbit is inclined at an angle of 5° 8´ to the Ecliptic. The line of Apsides joins the points of Perigee and Apogee and precesses over 8.85 years. The Moon crosses the same node every 27.2122 days (the Draconic month) The Nodes precess in a retrograde motion over a period of 18.6 years. Lunar and Solar eclipses can only occur when the line of the nodes point towards the Sun, roughly every 5.4 months. The type of eclipse will depend on the Moon’s orbital circumstance. Martin Crow Crayford Manor House Astronomical Society

  21. Images showing the apparent size difference due to the Moon’s non circular orbit and also Libration. Martin Crow Crayford Manor House Astronomical Society

  22. Eclipses How does a solar eclipse occur. Martin Crow Crayford Manor House Astronomical Society

  23. Solar eclipses occur in cycles called Saros cycles. The Saros cycle is based on the recognition that 223 synodic months approximately equal to 242 draconic months and 239 anomalistic months. Each Saros series is given a number. Odd numbers are used for solar eclipses occurring at the ascending node and evens for the descending node. The opposite is true for Lunar eclipses. At this time there are 41 different Saros series in progress. Each series lasts for between 1226 and 1550 years depending on the geometry. During the life time of a series of eclipses the path for odd numbered Saros series will travel from south to north and visa versa. Martin Crow Crayford Manor House Astronomical Society

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  26. Annular eclipse Total eclipse showing the solar corona A Solar eclipse will only last a few minutes and depends on the geometry of the Earth, Sun, Moon alignment. The totally eclipsed Sun is safe to look directly at. Bright stars and any visible planets will be seen in the sky. Martin Crow Crayford Manor House Astronomical Society

  27. The 1919 Solar eclipse observed by Sir Arthur Eddington gave observational evidence that proved the Einstein’s theory of general relativity was correct. Martin Crow Crayford Manor House Astronomical Society

  28. Martin Crow Crayford Manor House Astronomical Society Cornwall 1999 Aug 11 MVCrow

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  30. The 2006 Turkey eclipse as seen from the ISS. Martin Crow Crayford Manor House Astronomical Society

  31. Diamond ring China 2008 Aug 01 MV Crow Martin Crow Crayford Manor House Astronomical Society

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  33. Eclipses How does a lunar eclipse occur. Martin Crow Crayford Manor House Astronomical Society

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  37. The Planets Martin Crow Crayford Manor House Astronomical Society

  38. Mercury Average distance from Sun = 57.9 x 10⁶ km Diameter = 4,878 km Albedo = 0.068 (Bond) Has quite an eccentric orbit Has a 3:2 resonance so it rotates three times for every two orbits. Takes 88 days to complete one orbit. (Sidereal period) The synodic period is 115.9 days. Martin Crow Crayford Manor House Astronomical Society

  39. Venus Average distance from Sun = 108.9 x 10⁶ km Diameter = 12,102 km Albedo = 0.9 (Bond) Takes 224.7 days to complete one orbit. (Sidereal period) The synodic period is 583.9 days. Very dense atmosphere of CO₂ with a surface pressure of 93 bar (Earth = 1 bar) Surface temperature of 460° C Martin Crow Crayford Manor House Astronomical Society

  40. Mars Average distance from Sun = 227.9 x 10⁶ km Diameter = 6,792 km Albedo = 0.25 (Bond) Takes 687 days to complete one orbit. (Sidereal period) The synodic period is 780 days. Very thin atmosphere of CO₂ with a surface pressure of 0.006 bar (Earth = 1 bar) Surface temperature of -87° C to 20°C. Mars has two moons – Phobos and Deimos both probably captured asteroids. Martin Crow Crayford Manor House Astronomical Society

  41. Jupiter Average distance from Sun = 778.6 x 10⁶ km Diameter = 142,984 km at equator Albedo = 0.34 (Bond) Takes 11.9 years to complete one orbit. (Sidereal period) The synodic period is 399 days. Atmosphere of Hydrogen with a rocky core overlaid by a deep layer of metallic hydrogen. Martin Crow Crayford Manor House Astronomical Society

  42. Moons of Jupiter – the Galilean moons. Io Europa Callisto Ganymede Jupiter has in total 65 confirmed moons. Martin Crow Crayford Manor House Astronomical Society

  43. Saturn Average distance from Sun = 1,422 x 10⁶ km Diameter = 120,536 km at equator Albedo = 0.34 (Bond) Takes 29.5 years to complete one orbit. (Sidereal period) The synodic period is 378 days. Atmosphere of Hydrogen with a small rocky core. Martin Crow Crayford Manor House Astronomical Society

  44. Moons of Saturn Saturn has at least 62 moons. Martin Crow Crayford Manor House Astronomical Society

  45. Saturn’s rings The rings are 93% water ice and very thin – 20 m !!! They are composed of objects ranging in size from mm to meters. Martin Crow Crayford Manor House Astronomical Society

  46. Uranus Average distance from Sun = 2,876 x 10⁶ km Diameter = 51,118 km at equator Albedo = 0.3 (Bond) Takes 84.3 years to complete one orbit. (Sidereal period) The synodic period is 370 days. Atmosphere of Hydrogen with a small rocky core. Rotates on its side relative to the plane of the solar system. Discovered 1781 March 13 by William Herschel. Martin Crow Crayford Manor House Astronomical Society

  47. Moons of Uranus Uranus has 27 known moons and a ring system. Martin Crow Crayford Manor House Astronomical Society

  48. Neptune Average distance from Sun = 4,503 x 10⁶ km Diameter = 49,528 km at equator Albedo = 0.29 (Bond) Takes 164.8 years to complete one orbit. (Sidereal period) The synodic period is 367.5 days. Atmosphere of Hydrogen, Helium and Methane with a small rocky core. Discovered 1846 September 23 by Urbain Le Verrier, John Couch Adams and Johann Galle. Martin Crow Crayford Manor House Astronomical Society

  49. Moons of Neptune Neptune imaged in Methane light and Showing Proteus, Larissa, Galatea and Despina. Neptune also possesses a ring. Martin Crow Crayford Manor House Astronomical Society

  50. Trans-Neptunian objects A trans-Neptunian object in 2:3 mean motion resonance with Neptune. For every 2 orbits that a plutino makes, Neptune orbits 3 times. Plutinos are named after Pluto, which follows an orbit trapped in the same resonance Plutinos form the inner part of the Kuiper belt and represent about a quarter of the known Kuiper belt objects (KBOs). Martin Crow Crayford Manor House Astronomical Society

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