Presentation on theme: "General Astronomy The Solar System The Inner Worlds."— Presentation transcript:
General Astronomy The Solar System The Inner Worlds
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
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 Keplers Laws
From antiquity to the 1700's, the known planets were Mercury Venus Earth Mars Jupiter Saturn The Planets
In 1781, the list became… The Planets Mercury Venus Earth Mars Jupiter Saturn Uranus
In 1801, the list was extended to The Planets Mercury Venus Earth Mars Ceres Jupiter Saturn Uranus
By 1841, the list of planets is … Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune The Planets
For the last 70 years, since 1930, the order of increasing distance from the Sun has been… Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto My Very Excellent Mother Just Served Us Nine Pizzas Inner Planets Outer Planets
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 –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, –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.
The Planets Mercury Venus Earth Mars Ceres Jupiter Saturn Uranus Neptune Eris Pluto My Very Excellent Mother Just Served Us Nachos The Dwarf Planets Haumea Makemake
The Solar System Viewing from above the Earth's north pole, the inner planets' orbits are too small to make out
The Inner Planets
We begin by looking at the Inner Planets and attempt to categorize their main features: Mercury Venus Earth Mars
Things to look for… Size Composition Atmosphere Temperature Moons Magnetic Fields Liquid Water Density –A combination of size and composition
Density The average density of an object is its mass divided by its volume Water1.0 gram/cubic centimeter Pine wood0.5 g/cc Iron7.9 g/cc
Substance/ObjectAlbedo Enceladus0.8 Europa 0.6 forest granite grass Mars 0.25 Moon 0.12 sand snow0.6 soil urban areas % of incident light is reflected Albedo 0.0 Albedo 1.0
Eccentricity Most planetary orbits have eccentricities near 0 (a perfect circle)
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.
Mercury Statistics Mass (Kg)3.303E+23 Radius (Km) Density (g/cc)5.43 Orbital Radius (AU) Rotational Period (days) Orbital Period (days) Eccentricity Tilt of Axis (degrees)0 Orbital Inclination (degrees)7.004 Albedo0.10 Minimum Surface Temperature-173 ºC (-279 ºF) Maximum Surface Temperature+427 ºC (801 ºF) Atmospheric CompositionHelium 42% Sodium 42% Oxygen 15% Other 1%
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"
Mercury's Rotation and Year Click the Sun to start a cycle
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.
Mercury's Interior Crust Mantle Iron Core
Surface Features Fault Line Caloris Basin (Looks a lot like the Moon)
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
Venus' Statistics Mass (Kg)4.869E+24 Radius (Km) Density (g/cc)5.25 Orbital Radius (AU) Rotational Period (days) Orbital Period (days) Eccentricity Tilt of Axis2.64 Orbital Inclination3.394 Albedo0.65 Mean Surface Temperature482 ºC (900 ºF) Atmospheric Pressure (bars)92 Atmospheric CompositionCarbon Dioxide 92% Nitrogen 3+ % Other trace
Venus' Interior Atmosphere Crust Mantle Core
Topography While we can't see through Venus' cloud cover with visible light, radar is able to show us what the surface 'looks' like…
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
Earth's Statistics Mass (Kg)5.976E+24 Radius (Km) Density (g/cc)5.515 Orbital Radius (AU)1.0 Rotational Period (days) ( hrs) Orbital Period (days) Eccentricity Tilt of Axis23.45 Orbital Inclination0.00 Albedo0.37 Mean Surface Temperature15 ºC (59 ºF) Atmospheric Pressure (bars)1.013 Atmospheric CompositionNitrogen 77% Oxygen 21% Other 2%
Earth - Radar View
The Night Sky of Earth
North America by Night
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.
Mars' Statistics Mass (Kg)6.421E+23 Radius (Km) Density (g/cc)3.94 Orbital Radius (AU) Rotational Period (days) Orbital Period (days) Eccentricity Tilt of Axis25.19 Orbital Inclination1.850 Albedo0.15 Minimum Surface Temperature-140 ºC (-220 ºF) Maximum Surface Temperature 20 ºC (68 ºF) Atmospheric Pressure (bars)0.007 Atmospheric CompositionCarbon Dioxide 95.3 % Nitrogen 2.7 % Other 1+ %
The Martian Family
Weather on Mars
Mar's Interior Crust Mantle Core
The Explorers Curiosity self-portrait Opportunity simulated Spirit Pathfinder
Mars Surface Martian rovers Opportunity and Spirit are uncovering more and more evidence of an ancient wet planet Spirits path as seen from Mars Global Explorer
Mars Surface Approaching Columbia Hills
Mars Surface Endurance Crater
Mars – From 'Spirit'
The next image was sent from the 'Spirit' rover from the Martian surface just before breaking down.