Astronomy 101 chapter 6
Astronomy 101 chapter 6 ASTR 101
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This 0 page Class Notes was uploaded by Breanab on Monday March 21, 2016. The Class Notes belongs to ASTR 101 at University of New Mexico taught by Trace Tessier in Spring 2016. Since its upload, it has received 19 views. For similar materials see Introduction to Astronomy in Astronomy at University of New Mexico.
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Date Created: 03/21/16
Lecture 6 Finishing slide set 7 Asteroid belt 0 Possible planetesimals from a planet going to be formed but scattered The few left behind makes the belt Remaining gas left over from new planets gets swept out by intense periods of solar wind activity Planetary Ejection Solar system expanded by gravity pushing planetesimals from out side of the general orbit to the Kuiper belt and planetesimals from inside the orbit to the Oort cloud Starting slide set 8 The Earth 0 General features for comparison only not on test 0 Mass is 6x10quot24 kg 0 Radius is 6378 km 0 Density is 5500 kgmquot3 0 Age is at least 46 billion years 0 Why does the earth have an atmosphere while the mood does not 0 Because of gravity 0 Escape speed Earth 11 kms Moon 24 kms o Neglecting other effects the earth should reradiate all of the energy received from the sun giving the earths surface temurature of 250 K 23 C 0 Why is the average temperature of earth so mush higher about 40 C higher The greenhouse effect solar radiation is absorbed by the earth and the atmosphere that traps heat 0 What type of EM radiation do the greenhouse gases in our atmosphere trap o infrared o What type of EM radiation does the ozone layer in the upper part of our atmosphere protect us from 0 UV 0 What are the major layers in the interior of the Earth 0 The crust o The mantle semi solid rock cracks allow material to rise volcanoes o The outer core core temperature is 6000 K molten rock 0 The inner core solid metallic The magnetosphere The atmosphere The hydrosphere Like all waves seismic waves bend or refract S waves are unable to travel in liquid 0 Measurement of seismic waves give info on density of earths interior and which layers are solidmolten How does density change with depth 0 Becomes more dense the deeper down 0 What about temperature Becomes hotter the deeper down 0 What does the differentiation exhibited by the Earth tell us about its past 0 Different chemical elements have made their way to different layers of the earth the heavier ones making their way to the center while the lighter and lesser elements are on the outskirts Since solids cant separate themselves by density the phase of matter as a whole in the beginning had to be molten to allow the heavier elements to sink down to the center As the earth cooled certain parts of the earth solidi ed What were the two main sources of heating experienced by the earth in its history 0 The Sun not main 0 Collision energy 0 Radioactivity decay energy 0 Earths interior structure 0 Density increases with depth differentiation 0 Earth must have been molten once allowing denser material to sink as it started to cool and solidify 0 Heating due to bombardment and radioactivity Activity on the earths surface 0 Plates moving at a few cmyear 0 Continental drift or plate tectonics 0 Water brought to earth through bombardment and the water was contained What types of geological features or processes would you expect near plate boundaries Canyons mountains trenches volcanoes earthquakes Head on collisions Subduction zone one slide under the other Rift zone two plates moving apart Sliding past each other What is the driving force behind the motion of the plates 0 Convection planets ride on top of convection cells 0 One cycle takes millions of years heat loss is extremely low What causes the tides o Tides are due to the moons gravitational pull being stronger on the side of earth closest to it sun also in uences tides o Tidal in uence is a stretching effect When are the highest and lowest tides seen 0 Two high tides and two low tides per day high and low tides are twelve hours apart 0 Highest high tide and lowest low tide during the new moon and the full moon 0 During the rst and third quarter the tides aren t as extreme O O O O O The moon Lunar structure The crust highlands due to higher elevation lighter in color is 60 km thick on earth side and 150 km thick on far side Maria is the dark areas made of mantle materials mainly basalt Connected to more recent lava ows Moon is composed of material very similar to earths mantle 0 Many craters due to meteorite impacts only important source of erosion o Highlands have 10x the crater density of maria highlands are older Formation is unsure three theories 0 Fission the material that would be the moon was thrown off the earth 0 Problem earth doesn t spin fast enough Coformation the moon and the earth formed out of the same material at the beginning of the solar system 0 Problem moon has different density and composition 0 Capture the moon was a stray body captured into orbit around earth 0 Problem an extremely unlikely event Another theory added Impact early in the solar system a mars sized object hit the forming earth ejecting material from the mantle which coalesced to form the moon Computer simulations suggest this is plausible