Dr Bruce Elmegreen CHAPTER 16

n Epilogue – Dr Bruce Elmegreen CHAPTER 16 There is what seems to be, and there is what is. We look but we cannot see what is. We build instruments that do our looking and still these instruments cannot see everything. There is no limitless gaze. The horizon curves, the fog muffl es, the lights and structures get fainter and fuzzier with distance. The redshift dims. Peeling back one layer leads only to another. This is the reality of the Universe in which we live. When we think we have it just right, we see an unimagined new rightness beneath. David Block and Kenneth Freeman have been looking and measuring, classifying and pon- dering the Universe for a long time. We are fortunate they shared their story with us. This is a story about the avalanche of insight that follows the discovery of new techniques: of giant telescopes built by hand all around the globe and of the mysteries the builders solved and revealed through their drawings; of the photographic process and the replacement of vision by chemical images; of electronic antennae, cameras, telescopes, and satellites that are sensi- tive to radio, infrared, ultraviolet, x-ray, and gamma ray light. It is a story of the shrouds of the night that were slowly peeled back, of galaxies viewed both inside and out, like the x-ray fi sh in Collette Archer’s painting below. The Universe around us is rich with structure in both density and temperature. Some of this structure reveals itself by the light it radiates, the long or the short wavelengths depending on temperature and extinction, the bright or the dim light depending on distance, opacity, and power. Other structures emit no light at all, but show their presence only through gravity. Perhaps still others show their presence only through feeling. This is a very different Universe close to us than the Universe long ago and far away, which had much less structure, much more uniformity in temperature and density, and many fewer types of objects. It had no stars, no carbon or oxygen or other heavy nuclei, no galaxies An Epilogue – just elementary particles and their mutual forces. How that Universe, now mapped and 401 measured with modern instruments, turned into the Universe around us, is a story being told by countless pixels of digital data, month-long simulations on the largest comput- ers, and atom smashers that probe Big Bang energy densities. How that Universe sprung forth life that ponders and questions as we do is a story that still lies behind the thickest shroud. Dr Bruce Elmegreen is a senior research scientist at the IBM TJ Watson Research Center in New York. He completed his doctorate at Princeton University; his supervisor was the late Lyman Spitzer Jr, one of the fathers of modern astrophysics after whom the Spitzer Space Telescope is named. Dr Elmegreen then spent three years as a Junior Fellow in the Society of Fellows at Harvard University and joined IBM in 1984, after holding a Shrouds of the Night 402 faculty position at Columbia University. Dr Elmegreen was awarded the Dannie Hein- eman Prize in 2001 for theoretical studies of the interstellar medium, starbursts and the dynamics of spiral arms and bars in galaxies. A previous recipient of this prize was coauthor Kenneth Freeman. Dr Elmegreen has served on all three of the international Scientifi c Organizing Steering Committees for conferences on galaxy morphology and cosmic dust held on South African soil. Dr Elmegreen’s winning design for a medal to commemorate the Transit of Venus in 2004 was struck in both gold and silver. A gold medal was awarded to Dr Elmegreen by the Governor of the Reserve Bank of South Africa, Tito Mboweni. An Epilogue 403 Figure Captions CHAPTER 1 Figure 1 A view of Galileo’s town of birth, Pisa, as depicted in a leaf from Figure 6 In Middle-Age Europe, the Northern Lights were thought to the Nuremberg Chronicle published over 500 years ago, in 1493. The be refl ections of heavenly warriors. According to legend, soldiers who Nurmberg Chronicle (Liber Chronicarum) was written by the Nuremberg gave their lives for their king and country were allowed to battle on the physician Hartmann Schedel and was printed by Anton Koberger. skies forever, as a posthumous reward. (Reproduced from Photographic Atlas of Auroral Forms published by the International Geodetic and Figure 2 Papua New Guinea: the land of dancing masks. A photograph Geophysical Union, Oslo, 1930.) of an Asaro Mudman seen wearing his mask, in the Eastern Highlands of Papua New Guinea. Just as masks cover or shroud the human face, Figure 7 The grandeur of the Milky Way Galaxy celebrated by a group so too is our perception of the night sky inextricably intertwined by the of Aboriginals in Australia during a “walkabout.” Writes Aboriginal art- presence of cosmic masks. (Photograph: David L. Block.) ist Collette Archer: “Our people always use the stars to fi nd their way on walkabouts during the nights … Our people celebrate the full moon Figure 3 Customs in Papua New Guinea have remained unchanged for and dance with happiness. They always admire the stars as do myself.” centuries. Photographed near the town of Goroka is a group of Asaro (Artwork: Collette Archer, of the tribe Djunban in Far Northern Mudmen, wearing their haunting masks. In astronomy, cosmic dust grains Queensland, Australia.) act as enormously effective masks – much like a fog on Earth. An awesome new view of the cosmos unfolds as these cosmic masks are “penetrated” Figure 8 A stellar nursery, the Rosette Nebula, in our Milky Way Galaxy. using state-of-the-art infrared technology. (Photograph: David L. Block.) Young stars born toward the central regions of the Rosette Nebula have evacuated a grand cosmic cavity or “hole.” Seen silhouetted in the Figure 4 From the land of Papua New Guinea where masks still dance, a Rosette are numerous dark and imposing “elephant trunk” structures of human face is partially covered in a painted mask. The full moon itself is a cosmic dust. (Photograph: David L. Block.) mask, for it masks (or hides) myriads of fainter stars. In its brilliant light, only the very brightest of stars are seen. (Photograph: David L. Block.) Figure 9 Another view of the Rosette Nebula, secured at the European Southern Observatory on a mountain in the Atacama desert in north- Figure 5 What a foreboding sight the dancing Northern Lights, the ern Chile. The image has been photographically enhanced, to reveal Aurora Borealis, must have been, in an era when no scientifi c explana- features of exceptionally low surface brightness which are not appar- tion was known. (Reproduced from Photographic Atlas of Auroral Forms ent upon inspection by eye of the original glass negative. The Rosette published by the International Geodetic and Geophysical Union, Oslo, Nebula presents myriads of globules of cosmic dust. (Photograph: David 1930.) L. Block.) Figure Captions 405 Figure 10 The Seagull Nebula. Towering dynamics are at work here; a grains in interstellar space and photons from young, energetic stars gradu- veritable cosmic sculpture in the making. Bright rims of gas form ridges ally eroding the dark, dusty clouds. (Photograph: David L. Block.) upon dark clouds of dust. The Seagull’s head is located on the border of the constellations of Monoceros and Canis Majoris and it, too, is char- Figure 16 Resembling a seahorse, the Horsehead Nebula in the con- acterized by a prominent dark ridge of cosmic dust. (Photograph: David stellation of Orion is not a mere hole or chasm in the sky, but rather a L. Block.) distinct physical entity of swirling gas and cosmic dust. The Horsehead Nebula (of approximate dimensions 2.7 × 1.8 light years) is gradually Figure 11 The dark Universe. The dusty Universe. An area of star for- being eroded by the intense radiation of an energetic, nearby star; its mation in the constellation of Carina, spawning dark, opaque globules estimated lifetime is about 5 million years. (Photograph: European of cosmic dust. Dark globules are often the sites for protostars – stars in Southern Observatory.) the process of being born. Some globules may have grotesque shapes whereas others are almost spherical. The latter may have diameters less Figure 17 Shrouds of the Night: The enigmatic spiral galaxy known than 10 000 times the Earth–Sun distance; others may span diameters of as the “Sleeping Beauty,” struts its dark lanes of cosmic dust in a most a few light years. (Photograph: David L. Block.) dramatic fashion. Our challenge was to penetrate these dusty shrouds or masks and unveil cold (minus 210 degrees Centigrade) and very cold Figure 12 A spectacular star-forming region in the constellation of (minus 250 degrees Centigrade) cosmic dust grains in galaxies beyond Carina, known as NGC 3576 (object number 3576 in the “New General the Milky Way. (Photograph: John Kormendy.) Catalogue”). Gargantuan arcs of glowing hydrogen gas are evident. This object was discovered by Sir John Herschel during his visit to the Cape Figure 18 Shrouds of the Morning: Early morning mists in Canberra, as of Good Hope, South Africa. He recorded it as “Faint; oval.” The image photographed from the slopes of Mount Stromlo. The obscuring effects has been photographically enhanced to reveal the intricate beauty of the of the mist are extremely pronounced – hiding much of the valley below arcs as well as the dark globules of cosmic dust. (Photograph: David L. – even though the mist itself may be of negligible mass. (Photograph: Block.) David L. Block.) Figure 13 Clouds of dust lie sprawling across this wide-fi eld image of Figure 19 A bushfi re in Australia.

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