produces meteor showers: overtime a comet will leave bits of dust along its orbit. If Earth passes through the comet’s orbit, we get a meteor shower. Since Earth crosses the comet orbit every year, meteor showers are regular events. Types of meteorites: Stonys: 94% of meteorite falls, rocky composition; Irons: 5% of meteorite falls, iron-nickel alloy; stony-irons: 1% of meterorite falls, mix of iron-nickel alloy and rocky material. Iridium: evidence of an impact; no dinosaur fossils in these rock layers, thin layer containing iridium from impactor, dinosaur fossils in lower rock layers. Likely impact site: chicxulub crater. 200km dia crater buried under northwest corner of yucatan peninsula, 65 mil yrs old. Small impacts happen almost daily, impacts large enough to cause mass extinctions are many mil of yrs apart. Most meteors are comet debris, but meteorites come from asteroid debris. The Sun: mass is roughly 2x 10^27 tons. Only 2% of the sun’s mass is made of elements other than H or He. Suns energy output =3.8x10^26 Watts. The sun generates enough energy in one second to power the US for 3.5 mil years. Use kelvin temp scale (all thermal motion ceases at 0K (absolute zero), water
freezes at 273 K and boils at 373k). The sun’s photosphere (surface) has a temp of about 5,800K. Thermal Radiation: hot, opaque objects emit thermal radiation, including stars or hot metal. Light has a spectrum that depends only on the object’s surface temp. Spectral curve: represent the composition of the light from an object with a spectral curve. wavelength (or color) of the light on the horizontal axis. Intensity (or energy output per second) on the vertical axis. Two properties of thermal radiation: hotter objects emit more light per unit surface area at ALL wavelengths- the 12k object dominates. The hotter an object is, the shorter the wavelength of its max output. 3000K: more red light than blue light, object appears red. 12000K: more blue light than red light, object appears blue. Color of thermal radiation can tell us an objects temp. Star’s life ->balance of gravity (compresses the star, ^ with mass)& pressure(pushes outward, prevents collapse//^ with temperature & density). When they are in balance=hydrostatic equilibrium, gives sphere shape. Where are stars born- young stars are found near nebulae (clouds of dust & gas in space) Types of Nebulae-> 1.Emission nebula: a hot star excites gas near it to produce emission lines (red in color, o-type stars, produces lots of UV lite) 2. Dark nebula: dense clouds of gas & dust that block light from distant stars & contain icy dust (temps ~ -405 F). STARS BORN HERE, called giant molecular clouds 3. Reflection nebula: star light reflects off dust in a cool nebula (blue in color-blue scatters more than red lite) Star Formation -> protostar-main sequence- red giant- yellow giant- red giant- planetary nebula- white dwarf -collisions convert falling energy of atoms into thermal energy, thus the temperature ^, considered a gas clump . Center becomes dense and forms a protostar ( wind remove material from cloud and reveals disk [size of our solar system]of gas/dust & the forming star-also detected by infrared). Then becomes Pre- main sequence star
You've reached the end of your free preview.
Want to read both pages?