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Charles Hakes Fort Lewis College 1 Charles Hakes Fort Lewis College 2 Large Scale Structure Charles Hakes Fort Lewis College 3 Outline • Homework (don’t forget them) • Final Monday, 9:45. • bring a scantron; good eraser, or extra scantron; sharp pencils • calculator • Review Hubble’s Law • Large Scale Structure Charles Hakes Fort Lewis College 4 Probable Job Opportunity • The Academic Success Program regularly funds Astronomy Tutors/ Study Group leaders. If you might be interested in this for next fall, please let me know via email. Charles Hakes Fort Lewis College 5 The Tully-Fisher Relation exists between the galaxy's luminosity and its: A) color. B) size. C) age. D) rotation. Charles Hakes Fort Lewis College 6 The Tully-Fisher Relation exists between the galaxy's luminosity and its: A) color. B) size. C) age. D) rotation. Charles Hakes Fort Lewis College 7 What method would be most appropriate to determine the distance to a nearby galaxy? A) Spectroscopic parallax B) Cepheid variables C) Hubble’s law D) Radar ranging Charles Hakes Fort Lewis College 8 What method would be most appropriate to determine the distance to a nearby galaxy? A) Spectroscopic parallax B) Cepheid variables C) Hubble’s law D) Radar ranging Charles Hakes Fort Lewis College 9 Large-Scale Structure Charles Hakes Fort Lewis College 10 Figure 16.3 Cosmic Distance Ladder Charles Hakes Fort Lewis College 11 Large-Scale Structure • Use the scale of 1m = 1 A.U. Charles Hakes Fort Lewis College 12 Large-Scale Structure • Use the scale of 1m = 1 A.U. • The Earth is 1 m from the Sun Charles Hakes Fort Lewis College 13 Large-Scale Structure • Use the scale of 1m = 1 A.U. • The Earth is 1 m from the Sun • The Nearest star is near Albuquerque Charles Hakes Fort Lewis College 14 Large-Scale Structure • • • • Use the scale of 1m = 1 A.U. The Earth is 1 m from the Sun The Nearest star is near Albuquerque The center of the Milky Way galaxy would be 4 times as far as the moon. Charles Hakes Fort Lewis College 15 Large-Scale Structure • • • • Use the scale of 1m = 1 A.U. The Earth is 1 m from the Sun The Nearest star is near Albuquerque The center of the Milky Way galaxy would be 4 times as far as the moon. • The Andromeda galaxy would be near Mars Charles Hakes Fort Lewis College 16 Figure 16.3 Cosmic Distance Ladder Charles Hakes Fort Lewis College 17 Large-Scale Structure • Redshift surveys of galaxies are used to determine the large-scale structure of the universe. Charles Hakes Fort Lewis College 18 Figure 16.9 First Galaxy Survey from the mid-1980’s Charles Hakes Fort Lewis College 19 Figure 16.10 The Local Universe Charles Hakes Fort Lewis College 20 Large-Scale Structure • Redshift surveys of galaxies are used to determine the large-scale structure of the universe. • Observed structure includes: • Strings • Filaments • Voids • The most likely explanation is a slice through “Bubbles.” • Only a few of these “slices” have been completed. Charles Hakes Fort Lewis College 21 Figure 17.1 Galaxy Survey Charles Hakes Fort Lewis College 22 Galaxy Survey • The universe is homogeneous - it looks the same everywhere • The universe is isotropic - it looks the same in all directions • Cosmological principle - the universe is isotropic and homogeneous. Charles Hakes Fort Lewis College 23 Tools to study structure.. Charles Hakes Fort Lewis College 24 Central Black Hole • http://www.astro.ucla.edu/~ghezgroup /gc/pictures/orbitsMovie.shtml • ~4x106 Solar Masses Charles Hakes Fort Lewis College 25 Quasars Charles Hakes Fort Lewis College 26 Quasars • Quasars are the active nuclei of very distant galaxies. (Cannot observe the “rest” of the quasar’s galaxy.) • Energy output ~1000x Milky Way. • Powered by material accreting onto a supermassive black hole. • Very large redshifts = Very distant. • Can use spectra to study closer material. Charles Hakes Fort Lewis College 27 Figure 16.12 Twin Quasar Charles Hakes Fort Lewis College 28 Figure 16.13 Gravitational Lens Charles Hakes Fort Lewis College 29 Figure 16.14 Einstein Cross Charles Hakes Fort Lewis College 30 Figure 16.15 Galaxy Cluster Lensing Charles Hakes Fort Lewis College 31 Figure 16.16 Dark Matter Map Charles Hakes Fort Lewis College 32 Figure 16.11 Absorption Line “Forest” Charles Hakes Fort Lewis College 33 Review Questions Charles Hakes Fort Lewis College 34 RR Lyrae stars helped astronomers to: A) Find the distance to nearby galaxies B) Determine the center of the Milky Way C) Verify spectroscopic parallax D) Complete the H-R diagram Charles Hakes Fort Lewis College 35 RR Lyrae stars helped astronomers to: A) Find the distance to nearby galaxies B) Determine the center of the Milky Way C) Verify spectroscopic parallax D) Complete the H-R diagram Charles Hakes Fort Lewis College 36 What does the Hubble constant measure? A) The density of galaxies in the universe B) The luminosity of distant galaxies C) The rate of expansion of the universe D) the speed of a galaxy of known redshift E) the reddening of light by intergalactic dust clouds Charles Hakes Fort Lewis College 37 What does the Hubble constant measure? A) The density of galaxies in the universe B) The luminosity of distant galaxies C) The rate of expansion of the universe D) the speed of a galaxy of known redshift E) the reddening of light by intergalactic dust clouds Charles Hakes Fort Lewis College 38 What method would not be appropriate to determine the distance to a nearby galaxy? A) Tully-Fisher relationship B) Cepheid variables C) Hubble’s law D) Type I Supernovae Charles Hakes Fort Lewis College 39 What method would not be appropriate to determine the distance to a nearby galaxy? A) Tully-Fisher relationship B) Cepheid variables C) Hubble’s law D) Type I Supernovae Charles Hakes Fort Lewis College 40 Olber’s Paradox Charles Hakes Fort Lewis College 41 Olber’s Paradox • Why isn’t the sky bright? • If the universe is infinite, no matter which way you look, you should see a star. Charles Hakes Fort Lewis College 42 Figure 17.2 Olbers’s Paradox Charles Hakes Fort Lewis College 43 Olber’s Paradox • Why isn’t the sky bright? • If the universe is infinite, no matter which way you look, you should see a star. • Since the sky is not bright, either… • Universe is finite. • Universe evolves with time. Charles Hakes Fort Lewis College 44 The Big Bang • At some time in the past, everything was at a single point. Charles Hakes Fort Lewis College 45 The Big Bang • At some time in the past, everything was at a single point. 1 Ho time = • When - Approximately 14 billion years ago. • The Big Bang provides the resolution of Olber’s Paradox Charles Hakes Fort Lewis College 46 Figure 17.3 Receding Galaxies - where was the Big Bang? • The Big Bang happened everywhere at once. Charles Hakes Fort Lewis College 47 Chapter 17 Ultra Deep Field - more than 1000 galaxies are in this picture. Total estimate for the universe - ~40,000,000,000. Charles Hakes Fort Lewis College 48 Chapter 17 Cosmology Charles Hakes Fort Lewis College 49 Cosmology • • • • How big is the universe? How long has it been here? How did it start? How long will it last? Charles Hakes Fort Lewis College 50 The Fate of the Universe • Will it keep expanding forever? • Will gravity cause it to collapse? Charles Hakes Fort Lewis College 51 From closest to farthest, which methods are used to find the distance to something? A) radar, spectroscopic parallax, Cepheid variables B) radar, RR Lyrae variables, spectroscopic parallax C) parallax, Cepheid variables, RR Lyrae variables D) Tully Fisher relation, Cepheid variables, parallax Charles Hakes Fort Lewis College 52 From closest to farthest, which methods are used to find the distance to something? A) radar, spectroscopic parallax, Cepheid variables B) radar, RR Lyrae variables, spectroscopic parallax C) parallax, Cepheid variables, RR Lyrae variables D) Tully Fisher relation, Cepheid variables, parallax Charles Hakes Fort Lewis College 53 Interstellar gas is composed mainly of: A) only hydrogen. B) some hydrogen, but mainly carbon dioxide. C) 10% hydrogen, 90% helium by numbers of atoms. D) 75% hydrogen, 25% helium by weight. E) ammonia, methane, and water vapor. Charles Hakes Fort Lewis College 54 Interstellar gas is composed mainly of: A) only hydrogen. B) some hydrogen, but mainly carbon dioxide. C) 10% hydrogen, 90% helium by numbers of atoms. D) 75% hydrogen, 25% helium by weight. E) ammonia, methane, and water vapor. Charles Hakes Fort Lewis College 55 What is the single most important determinant of the temperature, density, radius, luminosity, and pace of evolution of a protostar? A) its mass B) its composition C) its molecules D) its magnetic field E) its spin Charles Hakes Fort Lewis College 56 What is the single most important determinant of the temperature, density, radius, luminosity, and pace of evolution of a protostar? A) its mass B) its composition C) its molecules D) its magnetic field E) its spin Charles Hakes Fort Lewis College 57 Which of these lies ahead for our Sun? A) supernova of type II B) brown dwarf C) nova D) planetary nebula E) pulsar Charles Hakes Fort Lewis College 58 Which of these lies ahead for our Sun? A) supernova of type II B) brown dwarf C) nova D) planetary nebula E) pulsar Charles Hakes Fort Lewis College 59 A massive object, heavier than the Sun, which could fit inside a city, is a: A) asteroid B) white dwarf C) neutron star D) brown dwarf Charles Hakes Fort Lewis College 60 A massive object, heavier than the Sun, which could fit inside a city, is a: A) asteroid B) white dwarf C) neutron star D) brown dwarf Charles Hakes Fort Lewis College 61 It is easiest to spot a newly formed protostar with which types of telescopes? A) ultraviolet scopes at the South Pole, through the ozone hole B) radio telescopes with the VLA in New Mexico C) x-ray telescopes like Chandra, up in orbit D) visible light scopes on Mount Palomar E) infrared scopes on Mauna Kea Charles Hakes Fort Lewis College 62 It is easiest to spot a newly formed protostar with which types of telescopes? A) ultraviolet scopes at the South Pole, through the ozone hole B) radio telescopes with the VLA in New Mexico C) x-ray telescopes like Chandra, up in orbit D) visible light scopes on Mount Palomar E) infrared scopes on Mauna Kea Charles Hakes Fort Lewis College 63 Three Minute Paper • Write 1-3 sentences. • What was the most important thing you learned today? • What questions do you still have about today’s topics? Charles Hakes Fort Lewis College 64