Touring our Solar System Solar System includes: Sun 8 planets Asteroids Comets Meteoroids Jan 4 5:48 PM Jan 4 5:50 PM A planet's orbit lies in an inclined orbital plane Planes of seven planets lie within 3 degrees of the Sun's equator Mercury's is inclined 7 degrees Jan 4 5:50 PM Jan 4 6:36 PM The planets are separated into two groups Terrestrial Planets Mercury through Mars small, dense, rocky Jovian Planets Jupiter through Neptune large, low density, gaseous Massive Thick atmospheres composed of Hydrogen Helium, Methane, and Ammonia Jan 4 5:57 PM Pluto While Pluto was considered to be a planet when it was discovered in 2006 that classification was removed. A planet is "an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit" Pluto does not dominate its neighborhood. It does not draw in asteroids and does not orbit appropriately. It is also not significantly larger than its moon. Jan 4 6:01 PM 1
Formation of the planets Nebular Hypothesis (we already studied) Planets formed about 5 billion years ago from a dense gaseous nebula as the planets formed the materials that compose them separated. Due to their surface gravities Venus and Earth retained atmospheric gases. Due to frigid temperatures the Jovian planets contain a high percentage of ices The Big Bang Theory Accounts for galaxies moving away from us Universe was once confined to a "ball" that was supermassive, dense, and hot The Big Bang marks the inception of the universe and occurred about 20 billion years ago at which point all matter and space was created since then it began moving outward This outward expansion is evidenced by the Red Doppler Shift Jan 4 6:07 PM Jan 4 6:42 PM Red Shifts Doppler effect is a change in the wavelength of light emitted by an object due to its motion Movement away stretches wavelength, longer wavelength appears redder Movement toward squeezes wavelength, shorter wavelength appears bluer Large Doppler shift indicates high velocity Small Doppler shift indicates lower velocity Most galaxies exhibit a red Doppler shift which indicates that they are moving away, farther galaxies exhibit a greater shift The Moon Diameter 2150 miles Density 3.3 times that of water Comparable to Earth's crustal rocks gravitational attraction is 1/6 that of Earth's There is no atmosphere Tectonics are not active Discovered in 1929 by Edwin Hubble Hubble's Law: the recessional speed of galaxies is proportional to their distances Jan 4 6:45 PM Jan 4 6:09 PM Maria (Latin for "sea") Dark regions Fairly smooth lowlands originated from asteroid impacts and lava flooding the surface Lunar Surface Two types of terrain Highlands Bright, densely cratered regions Make up most of the Moon Make up all the "back" side of the Moon Older than maria Jan 4 6:34 PM Jan 4 6:12 PM 2
Lunar History Hypothesis suggests that a giant asteroid collided with Earth to produce the Moon One method used to work out lunar history is to observe crater density: older areas are more dense than younger ones. Moon evolved in three phases 1. As Moon formed its outer shell melted, cooled and solidified 2. Formation of maria and younger highlands 3. Formation of rayed craters Minor members of the solar system Asteroids: Most lie between Mars and Jupiter small bodies some have eccentric orbits many of the recent impacts of the Moon and Earth were collisions with asteroids Irregular shapes Uncertain origins Jan 4 6:15 PM Jan 4 6:18 PM Comets often compared to large "dirty snowballs" composed of frozen gases and rocky metallic materials origin is not well known Most famous short period comet is Halley's comet which has a 76 year orbital period Meteoroids called meteors when they enter Earth's atmosphere meteor shower occurs when Earth encounters a swarm of meteoroids associated with a comet's path Types are classified by their composition Irons Stony Stony irons Carbonaceous chondrites Jan 4 6:20 PM Jan 4 6:22 PM Our Sun One of 200 billion stars that make up the Milky Way galaxy Only star close enough to allow the surface features to be studied An average star Structure can be divided into four parts 1. Solar interior 2. Photosphere 3. Chromosphere 4. Corona Solar interior Cannot be observed directly Nuclear fusion occurs here It is estimated that the sun has enough fuel to last another five billion years Jan 4 6:25 PM Jan 4 6:28 PM 3
Photosphere "Sphere of light" Sun's surface actually a layer of incandescent gas less than 500km thick Grainy texture made up of many small bright markings produced by convection Most of the elements found on Earth also occur on the Sun Temperature averages approximately 6000K Chromosphere Just above photosphere lowermost atmosphere relatively thin, hot layer of incandescent gases top contains numerous spicules which are narrow jets of rising material Jan 4 6:29 PM Jan 4 6:31 PM Corona outermost portion of the solar atmosphere Very tenuous ionized gases escape from the outer fringe and produce the solar wind temperature at the top exceeds 1 million Kelvin Jan 4 6:32 PM Jan 4 6:33 PM Electromagnetic Radiation (EMR) How does energy from the sun reach the Earth? EMR is a transverse wave that travels without a medium The EM Spectrum is divided into pieces based on wavelength, energy and frequency of the light Radio waves Microwaves Infrared Visible Ultraviolet XRays Longer wavelength lower frequency Gamma rays Shorter wavelength higher frequency Sep 8 9:42 AM Sep 8 9:43 AM 4
All EMR travels at the speed of light c = 3.0 x 10 8 m/s Sep 8 9:48 AM Sep 8 9:57 AM 5