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General Astronomy The Solar System The Inner Worlds.

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1 General Astronomy The Solar System The Inner Worlds

2 The Solar System Generally speaking, the Solar System may be considered to be everything bound by the gravitational influence of the Sun. This, of course, includes Planets Moons Comets Meteoroids Asteroids Dust and gas And anything else confined to orbit the Sun

3 The Solar System We begin by examining the largest bodies in the solar system (excluding the Sun itself) --- The Planets All orbit the Sun in accordance with Kepler’s Laws

4 The Planets From antiquity to the 1700's, the known planets were
Mercury Venus Earth Mars Jupiter Saturn

5 The Planets In 1781, the list became… Mercury Venus Earth Mars Jupiter
Saturn Uranus

6 The Planets In 1801, the list was extended to Mercury Venus Earth Mars
Ceres Jupiter Saturn Uranus

7 The Planets By 1841, the list of planets is … Mercury Venus Earth Mars
Jupiter Saturn Uranus Neptune

8 The Planets For the last 70 years, since 1930, the order of increasing distance from the Sun has been… Mercury Venus Earth Mars Inner Planets Jupiter Saturn Uranus Neptune Pluto Outer Planets My Very Excellent Mother Just Served Us Nine Pizzas

9 Defining a Planet On August 24, 2006, the IAU resolved that planets and other Solar System bodies would be defined in the following way: A planet is a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and has cleared the neighborhood around its orbit. A dwarf planet is a celestial body that has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, has not cleared the neighborhood around its orbit, and is not a satellite. All other objects except satellites orbiting the Sun shall be referred to collectively as Small Solar-System Bodies.  

10 The Planets The Dwarf Planets Mercury Venus Earth Mars Ceres Eris
Jupiter Saturn Uranus Neptune Haumea Makemake Pluto My Very Excellent Mother Just Served Us Nachos

11 The Solar System Viewing from above the Earth's north pole, the inner planets' orbits are too small to make out

12 The Inner Planets

13 The Inner Planets We begin by looking at the Inner Planets and attempt to categorize their main features: Mercury Venus Earth Mars

14 Things to look for… Size Composition Atmosphere Temperature Moons
Magnetic Fields Liquid Water Density A combination of size and composition

15 Density The average density of an object is its mass divided by its volume Water 1.0 gram/cubic centimeter Pine wood 0.5 g/cc Iron 7.9 g/cc

16 Albedo Substance/Object Albedo Enceladus 0.8 Europa 0.6 forest
granite grass Mars   0.25 Moon   0.12 sand snow soil urban areas 60% of incident light is reflected Albedo 0.0 Albedo 1.0

17 Eccentricity Most planetary orbits have eccentricities near 0 (a perfect circle)

18 Mercury Mercury is a rocky, nearly airless world.
Closest to the Sun, it is both heat-seared and frozen. There are no moons and Mercury is heavily cratered. Physically it is smaller than Jupiter's moon, Ganymede, but it is the second densest planet in the Solar system thanks to its large, solid iron core There is a very small magnetic field, about 1% of the Earth's. This implies that Mercury's iron core is at least partially liquid.

19 Mercury Statistics Mass (Kg) 3.303E+23 Radius (Km) 2439.7
Density (g/cc) 5.43 Orbital Radius (AU) 0.3871 Rotational Period (days) Orbital Period (days) 87.969 Eccentricity 0.2056 Tilt of Axis (degrees) Orbital Inclination (degrees) 7.004 Albedo 0.10 Minimum Surface Temperature -173 ºC (-279 ºF) Maximum Surface Temperature +427 ºC (801 ºF) Atmospheric Composition Helium % Sodium % Oxygen % Other %

20 Mercury's Day For many years it was thought that Mercury was 'tidal locked' to the Sun. That means it always keeps one face to the Sun, rotating in synchronization with its orbit. We now know that this is wrong. Mercury does rotate on its axis in about 59 earth days (while its orbital period is about 88 days; this is a 3 to 2 ratio, 3 mercury "days" every 2 mercury "years"

21 Mercury's Rotation and Year
Click the Sun to start a cycle

22 Mercury Mercury has the most eccentric orbit of all the planets.
There is an odd phenomenon however… Mercury's orbit precesses. The point of perhelion changes very slightly each year. Note that this cannot be explained using Newton's Laws.

23 Mercury's Interior Crust Mantle Iron Core

24 Surface Features Caloris Basin (Looks a lot like the Moon) Fault Line

25 Transit

26 Venus No magnetic field, perhaps because of its slow rotation.
No satellites Venus' rotation is somewhat unusual in that it is both very slow (243 Earth days per Venus day, slightly longer than Venus' year) and retrograde The pressure of Venus' atmosphere at the surface is 90 atmospheres. It is composed mostly of carbon dioxide. There are several layers of clouds many kilometers thick composed of sulfuric acid. Venus' surface temperature is over 740 K (hot enough to melt lead). Physically it is close to earth only slightly smaller in size and less massive

27 Venus' Statistics Mass (Kg) 4.869E+24 Radius (Km) 6051.8
Density (g/cc) 5.25 Orbital Radius (AU) 0.7233 Rotational Period (days) Orbital Period (days) Eccentricity 0.0068 Tilt of Axis 2.64 Orbital Inclination 3.394 Albedo 0.65 Mean Surface Temperature 482 ºC (900 ºF) Atmospheric Pressure (bars) 92 Atmospheric Composition Carbon Dioxide % Nitrogen % Other trace

28 Venus' Interior Atmosphere Crust Mantle Core

29 Topography While we can't see through Venus' cloud cover with visible light, radar is able to show us what the surface 'looks' like…

30 Venus

31 Venus’ Surface

32 Earth A moderate atmosphere A magnetic field Geologically active
A single moon, but it is the largest in the solar system relative to its parent body. Prograde rotation 23.5 degree inclination to the ecliptic Presence of liquid water Prograde orbit Rocky

33 Earth's Statistics Mass (Kg) 5.976E+24 Radius (Km) 6378.14
Density (g/cc) 5.515 Orbital Radius (AU) 1.0 Rotational Period (days) ( hrs) Orbital Period (days) Eccentricity 0.0167 Tilt of Axis 23.45 Orbital Inclination 0.00 Albedo 0.37 Mean Surface Temperature 15 ºC (59 ºF) Atmospheric Pressure (bars) 1.013 Atmospheric Composition Nitrogen % Oxygen % Other %

34 Earth - Radar View

35 The Night Sky of Earth

36 North America by Night

37 Mars Rocky Very thin atmosphere Magnetic field
2 small moons, Phobos and Deimos Prograde rotation and orbit Possible presence of water frozen in deep gullys Geologically inactive at present, but has extinct volcanoes including Mons Olympus – largest, so far, in the explored solar system.

38 Mars' Statistics Mass (Kg) 6.421E+23 Radius (Km) 3397.2 Density (g/cc)
3.94 Orbital Radius (AU) 1.5237 Rotational Period (days) Orbital Period (days) 686.98 Eccentricity 0.0934 Tilt of Axis 25.19 Orbital Inclination 1.850 Albedo 0.15 Minimum Surface Temperature -140 ºC (-220 ºF) Maximum Surface Temperature 20 ºC (68 ºF) Atmospheric Pressure (bars) 0.007 Atmospheric Composition Carbon Dioxide % Nitrogen % Other %

39 The Martian Family

40 Weather on Mars

41 Mar's Interior Crust Mantle Core

42 The Explorers Curiosity Opportunity Spirit Pathfinder self-portrait
simulated Spirit Pathfinder

43 Mars’ Surface Martian rovers Opportunity and Spirit are uncovering more and more evidence of an ancient wet planet Spirit’s path as seen from Mars Global Explorer

44 Mars’ Surface Approaching Columbia Hills

45 Mars’ Surface Endurance Crater

46 Mars – From 'Spirit'

47 Mars – From 'Spirit' The next image was sent from the 'Spirit' rover from the Martian surface just before breaking down.

48 Size Comparisons


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