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CHAPTER ONE Introduction For thousands of yean men have looked into the sky. long with wonder and fear but eventually with comprehension. The regular motions of the sun and stan. the wandering of the moon and the planm. provided early insights Into cause and effect and the regularity of nature. With under- standing came the hope of controlling nature and the beginning of science and of technology. In this century, the rapid growth of science and tech- nology has increased the depth of our insight and also our wonder; al- though we have found much, we still have too few explanations. We know from past history that much new is yet to be found. Navigators and explor- ers of the terrestrial globe found new conti.nents inhabited by strange and different peoples. The explorers of the sky, however, have an almost un· limited sample of nature to study. They have found not merely interesting new details about individual stars or other objects but entirely new c.lasses of objects undreamed of ten years ago. As each new technology was ap- plied to study light (photons) of different colors or energetic particles of different charge and mass (cosmic rays, neutrinos), new types of worlds were revealed. The previously ..-ell-organized universe, whieh for ancients was a planetary system centered on the earth, exploded into a bewildering universe of new types of objects, large and small, with exotic new names and marvelous new natures. Technology, theoretical insight. deeper un- derstanding of the properties of matter, and the large computer. together with hard work, have made the last decade of astronomy one of the truly greatest periods in its history. Man has landed on his first planet-the moon. But hi.s mind and eye have traveled billion.s of light years into the

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2 ASTRONOMY AND ASTROPHYSICS FOR THE 1970's past and in the next decade will penetrate unimagined new worlds. Astronomy is a union of the science of the very small and of the very large. Astronomers are interested in the properties of nuclei. atoms, mole· cules. solids, planets. interstellar maner. and stars. But stars are them- selves units in larger aggregates-galaxies (Milky Ways) that agglomerate into clusters and extend throughout space as far as we can probe. There are more stars in our Milky Way (200 billion in number) than there are people who ever have lived on earth. How many other "earths" and what other types of' intelligent beings exist out there? There are probably nearly as ntany galaxies in the observable universe as there are stars in our Milky Way. What strange new types of objects do they contain? Are there forces and energies at work that we do not yet know of? We are bathed from all directions by weak radio signals, apparently a remnant of the creation of the universe, degraded from an enormous burst of light at the beginning o f time ten billion years ago. What was it like then? Does time stretch backward forever. or was there a beginning? What. if anything, came be- fore? Where do energy and matter come from? Is the total amount o f en ~ ergy and matter constant in time? The astronomer's daily life deals with such difficult questions. How many other planetary worlds are there. are they inhabitable. and are any inhabited? How long will the sun shine and the earth survive? The actual universe is stranger than lhat of science fiction; its explora- tion is one of the nobler adventures of the human mind. Like a child at play. the astronomer busies himself with strange toys-white dwarfs and red giants. pulsars and quasars-and in his theories moves the building blocks of atoms about to model something like the world he sees. with an imagination and a courage like a child's but with the resources of modern science and technology. It is fortunate that the pleasure he finds in the profession and the excitement of his discoveries are joys of science that are still communicable to the public. The optimism accompanying the ex- ploration of our own West ended with the disappearance of the frontier; but exploring the external frontier of the heavens is endless. and its reward is knowledge, a more humbling wealth. Most astronomers have worked from the ground. through a thin but unsteady a1mosphere. using 'isible light. near· and far-infrared radiation. and radio frequencies. With technological development of balloons, rock- ets. and satellites. we first rose above our turbid atmosphere to observe the different radiation from the sky-gamma rays, x rays, and ultraviolet ra- diation-that are invisible from the surface of the earth. Soon we will ob- serve stars and galaxies extensively at the far-infrared wavelengths that are also blocked from reaching the surface of the earth, as are long radio wavelengt.hs. We will grow high-accuracy, high-resolution, x-ray eyes. The high cost of space technology and the initial relatively short life of sa tel·

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Introduction J lites, compared with the cost and lifetime of ground-based instruments, make astronomy in space seem risky and expensive but fully rewarding in its fantastic panoply of discovery. The present survey of astronomy attempts to cover the entire range of astronomy, ground-based and space-based. Allowing for the broadened scope of enquiry, we report on a wider range of topics than did the Whit- ford report. The scientific hopes expressed in that report underestimated what has been found in seven years. The facilities proposals of the Whit- ford report have in part been fulfilled by construction of two 150-in. telescopes for the national observatories in the northern and southern hemispheres. In radio astronomy. the large facilities proposed were not built. Nevertheless, radio astronomy made startling advances because of the ingenuity of the observers and the success of higher-frequency re- ceivers. Especially active now is the new field of the chemistry of interstel- lar space; in a brief period, 22 new molecules and 7 isotopes were dis- covered. Modern technology, the large computer. and existing facilities combined to produce muc.h of this recent progress. The universe is much more surprising than we thought it would be; technology improved more than was expected in that period. Objects were found that had not been thought of. and explanations based on new fields of physics were ad· vanced. We firmly expect that the decade for which our program is pre- pared will be at least as exciting. We can almost certainly guarantee that there will be more surprises than we contemplate and even more novel explanations of the mysterious universe into which our eyes and minds are just beginning to penetrate. There has been at least one central theme of the last seven years, which makes it like the age of Galileo. It is the discovery of the existence, almost omnipresence, of a high -energy, explosive universe. Much of our program is concerned with this new and violent world. Two universes coexist- hot and cold. The "hot" involves phenomena of explosion; very high tempera- ture; energetic cosmic rays; strange events in galaxies; new types of hot, dense, possibly young galaxies. By "cold" we mean ordinary stellar and interstellar matter, with temperatures from 50 million degrees down to a few degrees above absolute zero. Radio, cosmic-ray and x-ray observa- tions, gravitational waves, and large parts of optical and infrared astrono- my relate to the hot universe. Stellar. galactic, and extragalactic astronomy. in the large. refer to a cold universe. Much of what is found in the infrared points to even colder stars. dust. and gas than we had ex- pected would exist. The most rapid and currently exciting growth is in the realm of the hot universe. But over 90 percent of the mass of stars is in cool K and M dwarfs. a hundred times fainter than the sun. which can live uneventfully for hundreds of billions of years. From the time of the ancient Greeks to the mid-twentieth century, the

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4 ASTRONOMY AND ASTROPHYSICS FOR THE 1970's universe was conceived as an unchanging. or at best slowly changing. cos- mos of fixed stars. The first few decades of this century replaced this view with a steadily expanding universe of galaxies-each galaxy a majestic, slowly rotating collection of stars intertwined with dust and gases. As- tronomers searched for origins and life histories of stars (including our sun) with time scales of billions of years. The last decade of exciting discovery has added to that picture a general cosmic violence, exploding galaxies and quasars, an almost universal presence of high-energy particles and magnetic fields, and events suggest- ing relativistic collapse. Much of this new knowledge derives from years of observations with radio and optical telescopes and interpretations with theories from modern physics. The discovery of these explosive events has been made possible by a dramatic growth in the tools and techniques of observational astrophysics. In 1972, we can observe the universe in virtually any part of the electro- magnetic spectrum. from gamma radiation to long-wave radio radiation. We measure Oux of high-energy particles and may even have detected neutrinos and gravitational waves. In 1963. the Whitford report addressed itself to the needs of optical and radio astronomers, with a sidewise glance at the field of space astrenomy, then barely under way. The present study evaluated research programs using the complete range of observational techniques. many of which did not exist a decade ago. Space-based gamma-ray telescopes are measuring radiation from the center of our gal- axy. X-ray instruments are observing a pulsar and many variable, myster- ious x-ray stars. Some disturbed galaxies are strong x-ray emitters. An ultraviolet stellar space observatory has operated for four years. yielding new information on a previously inaccessible region. Advanced electronic methods of photon detection are used on optical telescopes to make ob- servations in minutes that required hours a decade ago, thereby ma king possible nn order-of-magnitude increase of information on very faint ob- jects. Cryogenically cooled bolometric and solid -state devices Oy in bal- loons and stratospheric aircraft, to measure invisible infrared heat pho- tons. They find that some energetic objects radiate most of their power at these wavelengths. Millimeter-wave radio telescopes have discovered com- pletely unexpected complex organic molecules in the interstellar medium, not unlike essential constituents of biologically active tenutrial mole- cules. Centimeter-wave radio telescopes halfway around the world from • each other operate together as interferometers to give much higher resolu- tion than the finest optical photographs. They re•·eal features in the struc- ture of quasars that change their appearance in a few months. Radar sys- tems make topographic maps of the invisible surface of the planet Venus, detecting mountains less than 1 km in height. Space solar telescopes study

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Introduction S the outer solar atmosphere where the temperature suddenly rises to tens of millions of degrees in hot spots in the extended solar corona. What do we say about the future? Chapter 2 contains our major recom- mendations. as selected from the extensive programs of our technical pan· els. These programs are presented in full detail with scientific justification in Volume 2 of this report. The cost breakdown of new programs follows., roughly separated into space and ground-based and by experimental or theoretical techniques. The costs of the new programs given are incre- mental to those of the existing programs of the National Aeronautics and Space Administration, the National Science Foundation. the Department of Defense. the Smithsonian Institution, and private and state universities and foundations, details of which costs are found in Chapter 4. One essential aspect of the future should be discussed prior to con- sideration of financial requirements. If the epigraph of these pages has any meaning. it is that the human mind vivifies science. creates and uses the instruments. rides in space, guides the telescope, the computer, or the theoretician's pencil. Does the required high-quality manpower exist? Do we have too much? The details of our study (see Chapter 4) show that the quality is high indeed. the diversity of training and experience wide, and the numbers adequate. But any further increase in the rate of production of new PhD's or of the numbers of institutions offering that degree should be encouraged only as an increase in the foreseeable employment demand justifies it. The excitement of the field of astronomy has been a major fac- tor in attracting many brilliant young men and women into the ranks of its professionals. The rate of production of new PhD's in astronomy has in- creased by a factor of 10 in the last decade. At latest count more than half of the PhD's working in astronomy received their degrees in other disci- plines-primarily in physics, recently some in chemistry. All in all, the current rate of production of highly qualified astronomers is better than adequate to meet the foreseeable needs of this country during the next decade, even if our entire set of new programs recommended in this report were to be carried out on schedule. The supply would be adequate. indeed, for the demands of known astronomy-related areas, as well as a reserve for new ones that might open up in the coming decade. The failure or federal support to increase significantly during the past few years has' had a particularly great impact on the support for young as· tronomers. In addition to large-scale facilities, we most strong,ly recom- mend increased funding of modest research grants to young people, as well as support of optical telescope auxiliaries and novel experimental facilities and programs in radio astronomy. We hope that this program will pem>it smaller research groups and younger scientists to remain com· petitive in some areas with larger institutions.

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6 ASTR ONOMY AND ASTROPHYSICS FOR TIIF 1970's From our entire study. we conclude that a balanced elTon is essential. It muS1 contain ground ·bascd optical and rad io telescopes and auxiliaries, which greatly increase their efficiency. There should be a well·planned space·astronomy program. one ultimate goal of which is a large space telescope. It must pr