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(Our) Planetary System PHYS 205
Constituents of the Planetary System • Central Star: • Sol – Our sun • Planets: • Mercury • Venus • Earth (Terra) • Mars • Jupiter • Saturn • Uranus • Neptune • Satellites: • Moon • and the others • Asteroids • Comets • Meteors • Small planets • Pluto • Ceres • Charon
Characteristics of Planets • Distance from the Sun • Mass • Chemical composition • Rotation • Surface temperature
Distances Distances to the inner planets are measured using trigonometry and parallax. Distances to the outer planets are calculated using Kepler’s Laws.
Newton’s Law of Gravitation Centripetal force: F = Mmv2/D Gravitational force: F = GMeMm/D2 Gravitational Force = Centripetal Force and v = 2pD/P Me = v2Rm/G = (4p2/G)(D3/P2)
Size and Volume Size can be determined from the distance and the angular size of the object. Planets are nearly perfect spheres. Volume of the planets can be calculated from their sizes.
Other Properties: • Period of rotation: • direct observation • radar waves • changes in the magnetic field • Age: • - determine the age from the rocks • halflife of radioactive elements
Five Kinds of Matter • Fluid • Plasma • Ice • Rock • Metal
Different Environments • Oxidized Environments • Inner planets (oxygen and sulfur abundant) • Reduced Environments • Jovian planets (hydrogen and nitrogen abundant)
Rocks and Minerals • Igneous Rock • Formed by cooling of molten material • Sedimentary Rock • Deposition of fragments of igneous rock • Metamorphic Rock • Chemical and Physical alteration • Primitive Rock • Original material of the Solar system
Planetary Atmospheres • Composition • Chemical constituents • Outgassing • Condensation clouds • Minor component
Will it look anything like "The Day After Tomorrow"? • BOULDER – The release of the movie "The Day After Tomorrow" is spurring discussion about global climate change with its depiction of giant storms and plummeting temperatures abruptly menacing the planet. But are the movie's climate scenarios plausible? • At the National Center for Atmospheric Research (NCAR), scientists who study the impact of rising industrial emissions on the world's climate say it is impossible for an ice age to strike within days, as happens in the movie. They warn, however, that climate change may have significant consequences for society in coming decades. • Movie scenario. Temperatures in New York City plummet from sweltering to freezing in hours. • Actual climate change. Temperatures in parts of the world could drop, but not nearly as rapidly or dramatically as portrayed in the movie. In a warmer world, additional rain at middle and high latitudes, plus melt from glaciers, will add more fresh water to the oceans. This could affect currents such as the Gulf Stream that transport heat north from the tropics and might result in parts of North America and Europe becoming relatively cooler. Even if this were to occur, it would take many years or decades because oceans move heat and cold much more slowly than the atmosphere. (Some ocean changes, however, such as the periodic warming of Pacific Ocean waters known as El Niño, may affect regional weather patterns within weeks.) • Movie scenario. Tornadoes strike Los Angeles and grapefruit-sized hail falls on Tokyo. • Actual climate change. Research has shown that climate change may lead to more intense hurricanes and certain other types of storms. In a hotter world, evaporation will happen more quickly, providing the atmosphere with more fuel for storms. In fact, scientists have found this is already happening with rain and snowfall in the United States. But even when scientists run scenarios on the world's most powerful supercomputers, they cannot pinpoint how climate will change in specific places or predict whether Los Angeles or other cities will face violent weather.
1979 Summer Arctic Sea Ice 2000 NASA Goddard Space Flight Center
On a much much larger timescale: Ice ages have a period of 200-250 million years Corresponding to the rotation of the Sun about the Milky Way.
On an intermediate timescale: Milankovitch cycles Eccentricity: Periodicity 100,000 years Axial Tilt: Periodicity 41,000 years Precession: Periodicity 23,000 years Combined effect still a speculation!!
Globally, temperatures are projected to rise an additional 2 – 5°C in the 21st Century Reason?? We are here
Why do we have changes in the climate now?? Carbondioxide and water vapor are transparent to visible light but not to infrared. Sunlight is in the visible, however the reflected light from the heated surface is in the infrared, so the reflected heat is trapped. -> The Greenhouse Effect
Greenhouse Gas levels in the atmosphere and planetary surface temperatures are inextricably linked CarbonDioxide Methane
The end is here!! • According to some Earth climate models, such a runaway greenhouse effect , involving liberation of methane gas from hydrates by global warming (Clathrate gun hypothesis), has caused the Permian-Triassic extinction event. It is also thought that large quantities of methane could be released from the Siberian tundra as it begins to thaw, methane being 21-times more potent a greenhouse gas as carbon dioxide. • The Permian-Triassic extinction event, sometimes informally called the Great Dying, was an extinction event that occurred approximately 251 million years ago, forming the boundary between the Permian and Triassicgeologic periods. It was the Earth's most severe extinction event, with about 96 percent of all marinespecies and 70 percent of terrestrialvertebrate species becoming extinct.
Basic Properties • Semimajor axis : 1.00 AU • Diameter : 12,756 km • Density : 4.6 gr/cm3 • Escape velocity : 11 km/s • Atmospheric • Pressure : 1.00 bar • Composition : %78 N2, %21 O2
Seismic Waves and the Interior Crust: Basalt under the oceans and granite under the continents. Few kms thick. Mantle: Solid/molten rock. 2900 km thick. Core: 7000 km diameter, molten iron+nickel, solid inner core.
Geological Processes: • On Earth they are mostly endogenic (coming from the inside). • Tectonic. • On other planets like Mercury it is exogenic (mostly caused by meteor impacts).
Magnetosphere: • Earth has a magnetic field. • Caused by the metallic core. • The extend is called a Magnetosphere. • Magnetosphere extends to about 10 Earth diameters.
The Atmosphere • Troposphere: Weather and planes, 10 kms • Stratosphere: 80 kms, Ozone layer O3, absorbs UV light, CFCs destroy. • Thermosphere: 400kms, very hot • Ionosphere: UV light ionizes atoms, reflects radio waves.