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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

  8. One possibility is that Theia formed in the Lagrangian point L4 or L5. Its growing mass and gravitational Perturbations caused it to be destabilised and collide with the Earth. Martin Crow Crayford Manor House Astronomical Society

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  10. 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. Also it is now thought that an additional smaller object formed at the same time andhad a slow impact with the Moon accounting for the difference between the near side and the far side topography. 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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  13. 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

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

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

  18. 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

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

  20. 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

  21. 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

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

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

  24. 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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  27. 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

  28. 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

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

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

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

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

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  37. The Planets etc. Martin Crow Crayford Manor House Astronomical Society

  38. The Planets Martin Crow Crayford Manor House Astronomical Society

  39. 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

  40. 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

  41. Surface contour map of Venus Martin Crow Crayford Manor House Astronomical Society

  42. 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

  43. Surface contour map of Mars Martin Crow Crayford Manor House Astronomical Society

  44. The Asteroids Ceres was the first one discovered and is named 1 Ceres and is a main belt Asteroid. With a diameter of 952 km Ceres is approx. ¼ the size of our Moon. It is now estimated that there are at least 750,000 asteroids larger than 1km and millions of smaller ones. Ceres contains approx. 1/3 of the mass all of the asteroids. NASA Galileo probe Martin Crow Crayford Manor House Astronomical Society

  45. There are three basic groups: C Types – dark carbonaceous, make up approx. 75% of the total. S Types – stony (silicaceous), relatively bright make up approx. 17% M Types – Nickel / Iron – relatively bright objects make up most of the rest. There are now a whole raft of sub groups as new subtle variations are recognised. A great deal of uncertainty still surrounds the exact make up of certain objects. It is now known that a lot of objects are just rubble piles. Martin Crow Crayford Manor House Astronomical Society

  46. It is thought that the asteroids formed at the same time as the rest of the Solar System 4.5 billion years ago. As Jupiter neared its current mass it disrupted this area of space ejecting a large percentage of the objects in it and halting the formation of any large body there. Simulations indicate that bodies larger than 120km formed prior to the Jovian disruption and that those smaller than this are the result of subsequent collisions. Martin Crow Crayford Manor House Astronomical Society

  47. Asteroid groups Martin Crow Crayford Manor House Astronomical Society

  48. Near Earth Asteroids Amors – orbit between Earth and Mars (1221 Amor – discovered 1932) Apollos – orbit > 1.0 a.u. (1862 Apollo – discovered 1932) Atens – orbit < 1.0 a.u. (2062 Aten – discovered 1976) Martin Crow Crayford Manor House Astronomical Society

  49. 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

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

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