ASTRONOMY EXAM 1 STUDY GUIDE
ASTRONOMY EXAM 1 STUDY GUIDE ASTR 121
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This 9 page Study Guide was uploaded by Anisa sudra on Tuesday April 21, 2015. The Study Guide belongs to ASTR 121 at University of Oregon taught by Scott Fisher in Spring 2015. Since its upload, it has received 228 views. For similar materials see ASTR 121 The Solar System in Astronomy at University of Oregon.
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Date Created: 04/21/15
ASTRONOMY EXAM 1 STUDY GUIDE 0 Science is not static it s a process 0 Telescope Gemini 0 Computerized vent gates for windweather conditions Built by RSF and colleagues Gives views of astronomical objects we cannot obtain our eyes 0 Used to study the interstellar medium and dust disks around stars 0 IR longer wavelength than visible light 0 IR cameras like OSCIR see wavelengths 20 times longer than we see 0 Like seeing heat wavesquot 0 Our eyes only see a little bit of the spectrum the colored part 0 Oscir sees the infrared part of the spectrum 0 What we see and oscir sees are extremely different Oscir sees what s inbetween stars This camera is sensitive to what these things emit a Orion photo example Dust grains gas etc 0 Different types of telescopes see different parts of the spectrum 0 Everything emits radiation and the temperature of the object determines how it will emit DESCRIBED BY THE PLANCK FUNCTION 0 Our eyes generally see about 10000 degrees f oscir camera can see about 100 degreed f infrared Interstellar medium is the gas and dust that exists between the stars 0 Many of the space pictures are of this 0 Looks dense but is very very diffuse 11 our modern view of the universe the distance light can travel in 1 year its not a year it s a distance 0 About 6 trillion miles N 10 trillion km 0 1 parsec 325 light years 0 light travels at a fixed speed 0 We look at it on a relative scale Not absolute scale ASTRONOMY EXAM 1 STUDY GUIDE 0 cosmic addressquot 0 earth is our home in the solar system look at opening graphic in the textbook scaleofuniversecom powers of 10 a large glowing ball of gas that generates heat and light through nuclear fusion 0 Fusion in the sun is how it generates its energy how it warms the earth 0 solar prominence eruptive events from the sun 0 they are pointed towards earth and make an aurora A strong prominence will be bad for the earth 0 Stereo satelite satellite pointed at the sun 0 109 earths will fir across the diameter of the sun diameter of autzen stadium approx 109 of you 0 the surface of the sun is called the photosphere You cannot stand on the sun The temperature of the surface is 5800 K o The mass of the sun is roughly 330000 earths o The distance to the sun is 93000000 miles Equal to 8 lightminutes how fast light can move in a minute your eyes are passive light you are seeing is in the past Also called 1 astronomical unit 0 OUR SUN IS A STAR WHY IT S CALLED THE SOLAR SYSTEM our solar system consists of our sun and all the planets and their moons rocky asteroids icy comets that orbit the sun milky way galaxy huge disk shaped collection of stars it contains more than 100 billion stars galaxy a great island of stars in space containing from a few hundred million to a trillion or more stars local group about 40 galaxies our galaxy the milky way is one of the two largest in this group superclusters the regions in which galaxies are and galaxy clusters are most tightly packed universe aka cosmos the sum total of all matter and energy that is all galaxies and everything in between them the universe is expanding Which means that the average distances between galaxies are growing overtime big bang the beginning and it happened about 14 billion years ago nuclear fusion the process in which lightweight atomic nuclei smash together and stickfuse to make heavier nuclei ASTRONOMY EXAM 1 STUDY GUIDE This box summarizes a few key astronomical definitions introduced in this chapter and used throughout the book Basic Astronomical Objects star A large glowing ball of gas that generates heat and light through nuclear fusion in its core Our Sun is a star planet A moderately large object that orbits a star and shines pri marily by reflecting light from its star According to a definition approved in 2006 an object can be considered a planet only if it 1 orbits a star 2 is large enough for its own gravity to make it round and 3 has cleared most other objects from its orbital path An object that meets the first two criteria but has not cleared its orbital path like Pluto is designated a dwaifplzmet moon or satellite An object that orbits a planet The term salelite can reler to any object orbiting another object asteroid A relatively small and rocky object that orbits a star comet A relatively small and icerich object that orbits a star Collections of Astronomical Objects solar system The Sun and all the material that orbits it including the planets dwarl planets and small solar system bodies Al though the term solarsystem technically refers only to our own star system solar means of the Sun it is olten applied to other star systems as well star system A star sometimes more than one star and any planets and other materials that orbit it galaxy A great island ol stars in space containing lroni a lew hundred million to a trillion or more stars all held together by gravity and orbiting a common center cluster or group of galaxies A collection ol galaxies bound together by gravity Small collections tip to a lew dozen galaxies are generally called groups while larger collections are called clusters supercluster A gigantic region ol space where many individual gal axies and many groups and clusters of galaxies are packed more closely together than elsewhere in the universe universe or cosmos The sum total of all matter and energy that is all galaxies and everything between them observable universe The portion of the entire universe that can be seen from Earth at least in principle The observable universe is probably only a tiny portion of the entire universe Astronomical Distance Units astronomical unit AU The average distance between Earth and the Stilt which is about 13950 million kilometers More technically 1 AU is the length ol the semimajor axis of Earth s orbit lightyear The distance that light can travel in 1 year which is about 946 trillion kilometers Terms Relating to Motion rotation The spinning of an object around its axis For example Earth rotates once each day around its axis which is an imaginary line connecting the North Pole to the South Pole orbit revolution The orbital motion 01 one object around another For eample Earth orbits around the Sun once each year expansion of the universe The increase in the average distance between galaxies as time progresses Note that while the universe as a whole is expanding individual galaxies and galaxy clusters do no expand a moderately large object that orbits a star it shines by reflected light Primarily made of hydrogen like other gas giants Rings are made of dry ice and pebbles a moderately large object that orbits a star THAT IS NOT THE SUN 0 May be rocky icy or gaseous in composition 0 The first exoplanets were discovered in the 1990 s 0 We now know about 1800 planets around other stars 0 As time progresses more and more planets will be discovered around stars 0 Current theories suggest that approximately 20 15 of stars in our galaxy have planets o All are too far away to see detail Which means that they re only dots on imagesquot for now 0 The discovery of these completely changes our place in the universequot again We know that the solar system is one of many planetary systems 0 This will be one of the defining discoveries of our generations time o The moon vs the usa 0 Diameter of the moon 2100 miles ASTRONOMY EXAM 1 STUDY GUIDE 0 Diameter of the earth 7900 miles 0 Earth is about 4x bigger than the moon 0 450 tons 14 years of continuous human occupation orbits the earth about 200 miles up 0 about the distance from Eugene to seattle 0 watch 155 timelapse 0 An object that orbits a planet or dwarf planet 0 A moon of Saturn ENCELADUS 0 Water ice fountains geysers These suggest that it might have liquid water below the surface and maybe life 0 Along with Europa moon of Jupiter are excellent places to search for extraterrestrial life 0 APRIL 4th cassini detects enceladus ocean 6 mile deep underground ocean of liquid water we measured what the density of the moon due to its gravity moving the spacecraft This could only happen with the presence of water mtively small and rocky object that orbits a star 0 Between mars and Jupiter 0 They are a failed planetquot 0 Ceres is the largest 600 miles in diameter 0 near earthquot asteroids ones who have orbits that cross the orbit of earth a relatively small and icy object that orbits a star 0 The ice allows the comet to form the tail of the comet o A comet s nucleus is about the size of a mountain 0 The tail is MUCH larger than that most are millions of miles long 0 The tail forms as ice and gas boils away as the comet nears the sun 0 Stuff in the comet tail dust water coZ methane ethane etc also all stuff that the comet is made off of 0 These materials come off of the nucleus and form the tail 0 it is made primarily of ice water and coZ dry ice 0 comets are thought to be the main source of the water on Earth ASTRONOMY EXAM 1 STUDY GUIDE 0 In earth s early formation cometary impacts brought the water a relatively small and icy object that orbits a star The ice allows the comet to form the tail of the comet A comet s nucleus is about the size of a mountain 0 The tail is MUCH larger than that most are millions of miles long 0 The tail forms as ice and gas boils away as the comet nears the sun 0 Stuff in the comet tail dust water coZ methane ethane etc also all stuff that the comet is made off of 0 These materials come off of the nucleus and form the tail it is made primarily of ice water and coZ dry ice comets are thought to be the main source of the water on Earth In earth s early formation cometary impacts brought the water 0 Raises the where did all the water on the planet come from Rosetta mission a spacecraft in orbit around a comet RIGHT NOW 0 Spacecraft will follow the comet around the sun 0 It released a lander named Philae that landed on the comet 0 Then it bounced and landed on the side of a cliff but it worked 0 on earth Philae weighed about 5kg but on the comet it weighed the amount of a paperclip a star and all the material that orbits it including its planets and moons The name of the sun is also sol gt ours is the solar system The Pluto situation Kuiper belt object an object with an orbit that extends beyond Neptune and into the Kuiper belt 0 There is not jus tone Pluto there are thousands o Pluto is kinda big and kinda near this is why it was discovered in 1930 o Pluto wasn t Demoted but PROmoted is id the first of a new class of object ASTRONOMY EXAM 1 STUDY GUIDE 0 Pluto was discovered when telescopes weren t as advanced as they are today the telescopes we have today allow us to see many other objects similar to Pluto o Pluto will be revisited soon by the new horizonsquot mission It will get to Pluto in 3 months from now But plutos gravity is not strong enough to hold down the mission so it will just fly by o LARGEST KNOWN KUIPER BELT OBJECTS Xena pluto 2005 fy9 2003 el61 sedan quaoar a great island of stars in space all held together by gravity and orbiting a common center 0 They are the largest single objects in all the universe 0 A galaxy like the milky way contains around 100 billion stars and probably at least that many planets 0 We cannot take a photo of the milky way bc we cannot get a camera that will capture the whole frame of stars 0 Andromeda galaxy m31 0 Types of galaxies 0 Spiral Younger galaxies o Elliptical As galaxies evolve and age they start out as spirals but then progress into elliptical galaxies the sum total of all matter and energy that is everything within and between all galaxies IMPORTANT gt THE FURTHER BACK WE LOOK IN THE DISTANCE THE FURTHER BACK WE LOOK IN TIME Andromeda is an analog of the milky way when will we be able to see what the Andromeda galaxy looks like now roughly 25 million years in the future back it will take the light that long to get from Andromeda to earth THE ULTIMATE SPEED LIMIT C 0 Light travels at a finite speed NOTHING can travel faster than this 0 186000 milessec N 7 times around the earth in 1 second 0 because of the fact that is takes light time to move we see objects as they were in the past ASTRONOMY EXAM 1 STUDY GUIDE The farther away we look in the distance the further back we look in time Hundred thousand light years across 0 Light year the distance that light can travel in 1 year about 6 trillion miles this is a unit of distance not time o All galaxies outside our local group are moving away from us 0 The more distant the galaxy the faster its racing away 0 Conclusion we live in an expanding universe 0 Galaxies that are farter away are moving away from us farther Liner relationship on hubble s law plot a galaxy 2 times farther away is moving away 2 times as fast 0 insert photo of plot o All galaxies outside the local group in all directions are moving away from us 0 Beginning of thought experiment Yesterdaythey were closer than todaylast year they were closer than this yearetc running the clock backwardsquot universe getting smaller and smaller In Which means implications bc the universe had a beginning ASTRONOMY EXAM 1 STUDY GUIDE In Which means we have measured the universethe universe is 1384 billion years old 0 We did this by measuring how fast the galaxy is moving 0 And by a spacecraft mapping the entire sky with temperature I THE BIG BANG what the beginning event is caHed n Observable universe what we can seepotentially observewe can only see 1384 billion light years away I There are roughly as many stars in the observable universe as there are grains of sand on all the beaches on earth 0 The big bang 0 Only hydrogen and helium and a little bit of lithium were created in this event 0 80 of you is carbon nitrogen oxygen 0 we are made of starstuff sagan how did we come to be Stars like the sun give out energy this energy warms us is a byproduct of fusion 0 Stars slowly convert to H and He into heavier elements 0 Elements are distributed throughout the galaxy by supernovae stellar winds 0 Clouds of gas and dust the ISM form into a new generation of stars Meaning for life We are the universe contemplating itself 0 You are not in the universe the universe is in you 0 How is earth moving in our solar system rotation spin rotates from west to east This is why the sun and stars appear to rise in the east and set in the west orbit revolution Astronomical Unit AU about 150 million kilometers earth s average orbital distance roughly 10000 particles 0 area of the sky is 110 of the size on the full moon ASTRONOMY EXAM 1 STUDY GUIDE 0 Took HST about 11 days to observable this deep 0 Selected to be the emptiest part of the sky The cosmic calendar 0 A scale on which we compress the history of the universe into 1 year There are roughly the same amount 13 spaceship earth 0 Earth rotates on an axis gt600 mileshr Earth orbits the sun gt60000 mileshr 0 Solar system moves among stars N 45000 mph Milky way rotates N 5000000 mph Milky way moves in local groups Universe ex ands Angular size 0 The angle it subtends at a given distance 0 It is not constant angular size decreases with distance 0 An objects physical size is how big it is o Is constant and does not change 0 the true and angular size of the moon stays the same whether or not it is near your horizon The illusion is your brain helpingquot you by doing what it thinks is best making the moon match the things that it sees as nexttoit o A region of thy sky 0 88 constellations fill the entire sky 0 The shapes are actually called asterisms aka constellations 0 stars at different distances all appear to lie on the celestial 5 here I Is the sun s apparent path through the celestial sphere The 88 constellations cover the celestial sphere
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