Infrared Astronomy – Seeing the Heat from William Herschel to the Herschel Space Observatory K23161_FM.indd 1 10/9/14 2:04 AM Infrared Astronomy – Seeing the Heat from William Herschel to the Herschel Space Observatory David L. Clements Imperial College London, UK K23161_FM.indd 3 10/9/14 2:04 AM CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2015 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Version Date: 20150608 International Standard Book Number-13: 978-1-4822-3728-3 (eBook - PDF) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. 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Contents List of Figures xiii Foreword: The Arp 220 Moment xix Preface xxi Author xxiii Chapter 1 Finding the Heat 1 1.1 REDDER THAN RED 1 1.2 THE ELECTROMAGNETIC SPECTRUM 3 1.3 THERMAL RADIATION 4 1.4 SPECTRAL LINES AND QUANTUM MECHANICS 7 1.5 THE STUFF OF THE UNIVERSE 11 1.6 A VERY BRIEF HISTORY OF THE UNIVERSE 15 1.7 THE PRACTICAL: TELESCOPES 16 1.8 OBSERVATIONAL STARS 18 1.8.1 Ground-basedtelescopes 18 1.8.2 Space-basedobservatories 23 1.9 CONCLUSIONS 28 Chapter 2 Feeling the Heat 29 2.1 THE PASTY DETECTOR 29 2.2 THE HISTORY OF ASTRONOMY: THE HISTORY OF DE• TECTION 29 2.3 ASTROPHOTOGRAPHY 32 2.4 MAKING ELECTRONS FROM PHOTONS 33 2.5 THE DIGITAL AGE 36 vii viii Contents 2.6 INTO THE INFRARED 39 2.7 LONGER WAVELENGTHS 41 2.8 INTO THE RADIO 44 2.9 THE ENEMY: WHAT GETS IN THE WAY 44 2.10 DEFEATING THE ENEMY: CLIMB A MOUNTAIN 48 2.11 FLY A PLANE, FLOAT A BALLOON, BUILD A ROCKET 50 2.12 THE OTHER ENEMY: BACKGROUNDS 52 2.13 CONCLUSIONS 53 Chapter 3 Local Heat 55 3.1 THE GREAT COLLISION OF 1994 55 3.2 LOCAL GEOGRAPHY: A TOUR OF THE SOLAR SYSTEM 56 3.3 INFRARED ASTRONOMY IN THE SOLAR SYSTEM 63 3.4 PLANETS • PEERING THROUGH CLOUDS, STUDYING ATMOSPHERES 63 3.5 MOONS: ICY, VOLCANIC, SMOGGY 65 3.6 ASTEROIDS 66 3.7 COMETS 69 3.8 THE OUTER SOLAR SYSTEM AND THE PROBLEM OF PLUTO 71 3.9 THE FORMATION AND EARLY EVOLUTION OF THE SO• LAR SYSTEM 71 3.10 THE DISCOVERY OF EXOPLANETS 73 3.11 CHARACTERISING EXOPLANETS 75 3.12 CONCLUSIONS 77 Chapter 4 The Heat of the Stars 79 4.1 THE STAR•FILLED SKIES 79 4.2 THE MAIN SEQUENCE 80 4.3 THE LIFE OF STARS 84 4.4 THE SIZES OF STARS 85 4.5 BEYOND THE BOTTOM OF THE MAIN SEQUENCE 91 4.6 WHEN IS A STAR NOT A STAR? WHEN IT’S A FREE FLOAT• ING PLANET 94 4.7 THE REMNANTS OF PLANET FORMATION 95 Contents ix 4.8 AGEING STARS, LOSING WEIGHT 97 4.9 STELLAR DEATH 100 4.10 SUPERNOVAE 101 4.11 CONCLUSIONS 103 Chapter 5 Young Heat 105 5.1 HOLES IN THE SKY 105 5.2 INTRODUCTION 105 5.3 THE INTERSTELLAR MEDIUM 106 5.4 FROM GIANT MOLECULAR CLOUDS TO COLLAPSING CORES 111 5.5 PROTOSTARSTOSTARS•THEBIGPICTURE 113 5.6 PLANET FORMATION 114 5.7 PROTOSTARS: THE OBSERVATIONS 118 5.8 GROUPS AND BINARIES 119 5.9 HIGH MASS STARS 124 5.10 THE ORIGIN OF THE INITIAL MASS FUNCTION 125 5.11 CONCLUSION 127 Chapter 6 Distant Heat 129 6.1 FORGETTING TO BREATHE 129 6.2 GALAXIES • STARS AND SO MUCH MORE 130 6.3 GALAXIES ACROSS THE ELECTROMAGNETIC SPECTRUM 136 6.4 M31: OUR NEAREST NEIGHBOUR 139 6.5 THE IRAS REVOLUTION 140 6.6 THE NORMAL UNIVERSE 141 6.7 THE ACTIVE GALAXY MENAGERIE 142 6.8 AGN UNIFICATION 145 6.9 GALAXIES AND AGN 149 6.10 STARBURST GALAXIES 151 6.11 GALAXY MERGERS 152 6.12 CONCLUSION 156 x Contents Chapter 7 Ancient Heat 159 7.1 LAUNCH DAY 159 7.2 GALAXY EVOLUTION 161 7.3 GALAXY EVOLUTION IN THE OPTICAL 165 7.4 REDDER FIELDS, HIGHER REDSHIFTS 168 7.5 THE MOST DISTANT GALAXIES KNOWN 172 7.6 THE COSMIC INFRARED BACKGROUND 174 7.7 SCUBA AND SUBMILLIMETRE GALAXIES 176 7.8 SUBMILLIMETRE GALAXIES AT OTHER WAVELENGTHS 179 7.9 THE HDF850.1 STORY 180 7.10 THE HERSCHEL REVOLUTION 181 7.11 THE MOST DISTANT DUSTY GALAXIES 183 7.12 GALAXIES AS TELESCOPES 186 7.13 ALMA • THE NEXT REVOLUTION 188 7.14 CONCLUSIONS 189 Chapter 8 FirstHeat 193 8.1 NOT EVEN WRONG 193 8.2 INTRODUCTION 194 8.3 THE DISCOVERY OF THE CMB 195 8.4 THE EVIDENCE FOR THE BIG BANG 197 8.5 A BRIEF HISTORY OF THE UNIVERSE 200 8.6 THE SEARCH FOR ANISOTROPY 204 8.7 NOISE IN THE DARKNESS 204 8.8 THE NUMBERS THAT MAKE A UNIVERSE 208 8.9 CMB OBSERVATIONS 213 8.10 THE PLANCK REVOLUTION 214 8.11 THE PLANCK VIEW OF THE UNIVERSE 216 8.12 CMB ANOMALIES 217 8.13 PROSPECTS FOR THE FUTURE 219 8.14 CONCLUSIONS 220 Chapter 9 Future Heat 221 9.1 THE DAWN OF A NEW MACHINE 221 Contents xi 9.2 WHAT REMAINS TO BE DONE 222 9.3 SPACE VS. GROUND 225 9.4 THE EUROPEAN EXTREMELY LARGE TELESCOPE (E•ELT) 227 9.5 OTHER GIANT TELESCOPES 229 9.6 THE JAMES WEBB SPACE TELESCOPE (JWST) 231 9.7 THE ATACAMA LARGE MILLIMETRE ARRAY (ALMA) 233 9.8 THE CERRO CHAJNANTOR ATACAMA TELESCOPE (CCAT) 234 9.9 THE SPACE INFRARED TELESCOPE FOR COSMOLOGY AND ASTROPHYSICS (SPICA) 236 9.10 EUCLID 236 9.11 CORE/PRISM 238 9.12 ASTRONOMY AS DATA SCIENCE 239 9.13 OTHER WAVELENGTHS 241 9.14 CONCLUSIONS 241 Chapter 10 Further Reading 245 10.1 CHAPTER 1: FINDING THE HEAT 245 10.2 CHAPTER 2: FEELING THE HEAT 245 10.3 CHAPTER 3: LOCAL HEAT 246 10.4 CHAPTER 4: THE HEAT OF THE STARS 246 10.5 CHAPTER 5: YOUNG HEAT 246 10.6 CHAPTER 6: DISTANT HEAT 246 10.7 CHAPTER 7: ANCIENT HEAT 247 10.8 CHAPTER 8: FIRST HEAT 247 10.9 CHAPTER 9: FUTURE HEAT 248 Bibliography 249 Index 261 List of Figures 1.1 William Herschel discovering infrared light. 2 1.2 The electromagnetic spectrum. 4 1.3 The spectrum of black body radiation at different temperatures. 6 1.4 Standing waves in a cavity. 8 1.5 A cat, Domino, as seen in the mid-infrared. 9 1.6 How energy levels produce spectral emission and absorption lines. 10 1.7 Diagrammatic representation of atoms of hydrogen, deuterium and helium, and an ion of helium. 13 1.8 Diagrammatic representation of nuclear fusion and fission. 14 1.9 The internal structure of protons and neutrons. 15 1.10 Diagram of a typical reflecting telescope. 17 1.11 UKIRT:theUKInfraredTelescope. 19 1.12 The Keck Telescopes. 20 1.13 The European Southern Observatory Very Large Telescope. 21 1.14 The James Clerk Maxwell Telescope. 22 1.15 Millimetre Valley on Mauna Kea. 24 1.16 The IRAS Satellite. 25 1.17 The WFC3 Instrument. 26 1.18 The ISO and Spitzer Satellites. 27 2.1 The Mark One Eyeball. 30 2.2 A 1910 diagram of a gold leaf electroscope [113]. 34 2.3 The operation of an electroscope. 35 2.4 The DECam camera, to be used for the Dark Energy Survey at the 4 m Blanco Telescope in Chile. 38 2.5 Impurities in a semiconductor. 39 2.6 Stressed infrared detectors. 40 2.7 How a bolometer functions.