Presentation on theme: "General Astronomy The Solar System The Inner Worlds."— Presentation transcript:
1 General AstronomyThe Solar SystemThe Inner Worlds
2 The Solar SystemGenerally speaking, the Solar System may be considered to be everything bound by the gravitational influence of the Sun.This, of course, includesPlanetsMoonsCometsMeteoroidsAsteroidsDust and gasAnd anything else confined to orbit the Sun
3 The Solar SystemWe begin by examining the largest bodies in the solar system (excluding the Sun itself) --- The PlanetsAll orbit the Sun in accordance with Kepler’s Laws
4 The Planets From antiquity to the 1700's, the known planets were MercuryVenusEarthMarsJupiterSaturn
5 The Planets In 1781, the list became… Mercury Venus Earth Mars Jupiter SaturnUranus
6 The Planets In 1801, the list was extended to Mercury Venus Earth Mars CeresJupiterSaturnUranus
7 The Planets By 1841, the list of planets is … Mercury Venus Earth Mars JupiterSaturnUranusNeptune
8 The PlanetsFor the last 70 years, since 1930, the order of increasing distance from the Sun has been…MercuryVenusEarthMarsInner PlanetsJupiterSaturnUranusNeptunePlutoOuter PlanetsMy Very Excellent Mother Just Served Us Nine Pizzas
9 Defining a PlanetOn 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 thatis 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, andhas cleared the neighborhood around its orbit.A dwarf planet is a celestial body thathas 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, andis 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 JupiterSaturnUranusNeptuneHaumeaMakemakePlutoMy Very Excellent Mother Just Served Us Nachos
11 The Solar SystemViewing from above the Earth's north pole, the inner planets' orbits are too small to make out
13 The Inner PlanetsWe begin by looking at the Inner Planets and attempt to categorize their main features:MercuryVenusEarthMars
14 Things to look for… Size Composition Atmosphere Temperature Moons Magnetic FieldsLiquid WaterDensityA combination of size and composition
15 DensityThe average density of an object is its mass divided by its volumeWater 1.0 gram/cubic centimeterPine wood 0.5 g/ccIron 7.9 g/cc
16 Albedo Substance/Object Albedo Enceladus 0.8 Europa 0.6 forest granitegrassMars 0.25Moon 0.12sandsnowsoilurban areas60% of incident light is reflectedAlbedo0.0Albedo1.0
17 EccentricityMost 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 coreThere 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)5.43Orbital Radius (AU)0.3871Rotational Period (days)Orbital Period (days)87.969Eccentricity0.2056Tilt of Axis (degrees)Orbital Inclination (degrees)7.004Albedo0.10Minimum Surface Temperature-173 ºC (-279 ºF)Maximum Surface Temperature+427 ºC (801 ºF)Atmospheric CompositionHelium %Sodium %Oxygen %Other %
20 Mercury's DayFor 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.
26 Venus No magnetic field, perhaps because of its slow rotation. No satellitesVenus' rotation is somewhat unusual in that it is both very slow (243 Earth days per Venus day, slightly longer than Venus' year) and retrogradeThe 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)5.25Orbital Radius (AU)0.7233Rotational Period (days)Orbital Period (days)Eccentricity0.0068Tilt of Axis2.64Orbital Inclination3.394Albedo0.65Mean Surface Temperature482 ºC (900 ºF)Atmospheric Pressure (bars)92Atmospheric CompositionCarbon Dioxide %Nitrogen %Other trace
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 rotation23.5 degree inclination to the eclipticPresence of liquid waterPrograde orbitRocky
33 Earth's Statistics Mass (Kg) 5.976E+24 Radius (Km) 6378.14 Density (g/cc)5.515Orbital Radius (AU)1.0Rotational Period (days)( hrs)Orbital Period (days)Eccentricity0.0167Tilt of Axis23.45Orbital Inclination0.00Albedo0.37Mean Surface Temperature15 ºC (59 ºF)Atmospheric Pressure (bars)1.013Atmospheric CompositionNitrogen %Oxygen %Other %
37 Mars Rocky Very thin atmosphere Magnetic field 2 small moons, Phobos and DeimosPrograde rotation and orbitPossible presence of water frozen in deep gullysGeologically 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) 3.94Orbital Radius (AU)1.5237Rotational Period (days)Orbital Period (days)686.98Eccentricity0.0934Tilt of Axis25.19Orbital Inclination1.850Albedo0.15Minimum Surface Temperature-140 ºC (-220 ºF)Maximum Surface Temperature20 ºC (68 ºF)Atmospheric Pressure (bars)0.007Atmospheric CompositionCarbon Dioxide %Nitrogen %Other %