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Astronomy and Astrophysics in the New Millennium 1 Recommendations
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Astronomy and Astrophysics in the New Millennium INTRODUCTION ASTRONOMY AND ASTROPHYSICS IN THE NEW MILLENNIUM The new millennium marks a turning point in the history of efforts to understand our place in the universe. The heavens have been a source of fascination for humanity for thousands of years, but only in the last few centuries has it been possible to take the measure of the stars—and only in the last few decades, to take the measure of the entire universe. The scientific and technical revolution that has enabled this enormous progress is accelerating. We can anticipate major new discoveries in the early decades of the new millennium, but more importantly we can anticipate major advances in our understanding of the universe—its origin, its evolution, its ability to support life, its destiny. What is the nature of the matter and energy in the universe? What happened at the dawn of the modern universe, when the first stars and galaxies formed? How are black holes formed? How do stars and planets form, and how do planets evolve to create habitats suitable for life? How does the astronomical environment affect Earth? These questions are all part of the fabric of science, cutting across traditional disciplines and government agencies and connecting the universe from the smallest to the largest scales. Addressing them will require interactions of astronomy with many other disciplines, including physics, mathematics, computer science, and biology. The interaction with physics is particularly important since all objects in the universe—and indeed the universe itself—are governed by the same fundamental physical laws. Answering these questions will alter the perception of our place in the universe, just as the advent of the heliocentric theory did centuries ago. The search for the answers can also capture the imagination of the public and inspire interest in science, thereby helping to create a more scientifically literate citizenry. ACCOMPLISHMENTS OF THE 1990S The past decade saw an unprecedented number of important astronomical discoveries. Some highlights include: Discovery of planets orbiting other stars; about three dozen are now known.
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Astronomy and Astrophysics in the New Millennium Determination of the interior structure of the Sun from observations of its seismic activity. These results confirmed theoretical models of solar structure throughout most of the Sun to within 0.1 percent and support the hypothesis that the observed deficit in the number of neutrinos from the Sun arises because they have a non-zero mass. Discovery of the Kuiper Belt, a large group of small, primitive bodies in the outer solar system predicted by theory. The Kuiper Belt is probably the source of most short-period comets and contains a unique fossil record of how the solar system formed. Observation of the impact of Comet Shoemaker-Levy 9 on Jupiter, providing a dramatic illustration of the potential effects of such impacts on Earth. Discovery of “brown dwarfs,” cool stars too small to sustain nuclear reactions in their interiors. Discovery of the theoretically predicted phenomenon of gravitational microlensing, in which the brightness of background stars is amplified by the gravitational effects of intervening objects of stellar mass. Discovery that gamma-ray bursts originate in the very distant universe and that they produce afterglows at other wavelengths, as had been predicted theoretically. Discovery of massive black holes in the nuclei of galaxies, including our own Milky Way, thereby confirming theoretical predictions that such massive black holes must be common. Discovery of young galaxies at redshifts greater than 3, revealing the dramatic evolution of galaxies from the early universe to the present. Discovery of theoretically predicted tiny fluctuations in the background radiation left over from the Big Bang on scales from 100 million to 10 billion light-years, the seeds of subsequent structure formation. Measurement of the expansion rate of the universe to an accuracy approaching 10 percent and determination that there is not enough matter to stop the expansion of the universe. At the end of the decade of the 1990s, evidence suggesting both that the universe is “flat,” as expected in inflationary cosmologies, and that its expansion is accelerating owing to the presence of “dark energy.” THE LEGACY OF THE PREVIOUS DECADAL SURVEY Planning and investment over the past decade are now providing ripe opportunities for advancements and discoveries in the near future. All of the large and many of the moderate programs recommended in
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Astronomy and Astrophysics in the New Millennium the report of the previous Astronomy and Astrophysics Survey Committee, The Decade of Discovery in Astronomy and Astrophysics (NRC, 1991; known as the Bahcall report and referred to in the current report as the 1991 survey), have been initiated. The top priority, the Space Infrared Telescope Facility (SIRTF), is scheduled for launch in 2002. SIRTF is the last of the Great Observatories, begun with the Hubble Space Telescope in the 1980s and successfully continued with the Compton Gamma Ray Observatory and the Chandra X-ray Observatory in the 1990s. SIRTF’s remarkable sensitivity in the infrared will enable it to make fundamental advances in the study of brown dwarfs, in tracing the formation and evolution of galaxies, and in better understanding quasars. The first of the two ground-based Gemini optical-infrared telescopes was completed in 1999, and the second is scheduled to open in 2001. Each telescope mirror has a diameter of 8 m. These telescopes will enable study of some of the same sources as SIRTF, but at shorter wavelengths and with much finer angular resolution. The Millimeter Array, which has become part of the more powerful Atacama Large Millimeter Array (ALMA), is nearing the end of its design phase with construction poised to start. ALMA will trace the processes by which interstellar gas turns into stars, on small scales in our galaxy and on much larger scales in the distant universe. Adaptive optics, the 1991 survey’s top-priority moderate program, advanced substantially during the 1990s and received a major boost with the selection of the Center for Adaptive Optics as a National Science Foundation (NSF) Science and Technology Center. By eliminating the smearing effects of the atmosphere, adaptive optics will enable astronomers to see fainter objects and far greater detail with existing ground-based telescopes. The Astrometric Interferometry Mission has evolved into the far more capable Space Interferometry Mission (SIM). Measuring positions on the sky with unprecedented precision, SIM will enable the discovery of planets much more similar to Earth in mass and orbit than those detectable now, and it should permit astronomers to survey the Milky Way Galaxy 1,000 times more accurately than is possible now. Through the National Optical Astronomy Observatories, the NSF has contributed to two new 4-m-class telescopes, providing powerful new tools for astronomical investigations. Studies of the cosmic microwave background radiation, the top priority of the Task Group on Space Astronomy and Astrophysics (NRC, 1997), are being pursued through NASA’s Microwave Anisotropy Probe (MAP), the European Space Agency’s Planck Surveyor mission, and a vigorous ground-based and
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Astronomy and Astrophysics in the New Millennium suborbital program. These studies will determine the large-scale properties of the universe and the fundamental cosmological parameters with remarkable precision. The dramatic increases in computer power foreseen a decade ago have been realized, enabling enormous advances in astrophysical simulation. We must begin planning now to take advantage of the discoveries these new facilities will make possible. Continued progress requires new ideas for the next generation of facilities and innovative plans for operating them most effectively. APPROACH AND SCOPE IMPLEMENTATION OF THE CHARGE To help carry out its charge (stated in full in the preface), the committee established nine panels with a total of 105 members.1 These panels developed the cases for all the projects and almost all the policies that were then evaluated and prioritized by the committee according to the criteria given below. The chairs of the panels participated in almost all the deliberations of the committee, but as advocates for their disciplines they did not vote on priorities. The majority of the panels were organized on the basis of observational technique rather than scientific subdiscipline, so as to facilitate selection of the projects to be considered by the committee. To treat issues that did not fit neatly into the panel organization, cross-panel working groups were established in four areas: (1) astronomical surveys, (2) extrasolar planets, (3) laboratory astrophysics, and (4) NSF-funded national observatories. The comments of these working groups provided input to the panels and to the committee. The committee also benefited from the National Research Council report Federal Funding of Astronomical Research (NRC, 2000), which addressed demographic and funding issues raised in previous astronomy surveys. In their deliberations, the panels and the committee received input from a broad cross section of the community. Sessions were held at two meetings of the American Astronomical Society (AAS), each attended by more than 300 people. The AAS also organized the Decadal Issues Discussion Forum on the World Wide Web, which attracted a number of thoughtful contributions. More than 100 individuals made presentations to the panels. Members of the committee and panel chairs organized
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Astronomy and Astrophysics in the New Millennium more than 20 meetings in their local institutions to gather further input. Hundreds of e-mail messages were received by the panels and the committee. Members of the committee consulted with representatives of the funding agencies and of the Office of Management and Budget and with congressional staff. Eight distinguished members of the international astronomical community2 attended most of the second meeting of the committee, adding valuable insights to the deliberations. International astronomers contributed to the work of the panels as well. The members of the panels and of the committee all share a primary expertise in astronomical science, and the scientific merit of the proposed programs was the primary basis for determining priorities. However, the committee also considered technical readiness, cost-effectiveness, impact on education and public outreach, and the relation to other projects, both in the United States and abroad. The committee made a careful attempt to define the boundary between projects it would consider and those it would not. First, judging that the Explorer and Discovery programs at NASA are suitably peerreviewed, the committee did not make any recommendations on individual projects in these programs. Second, for evaluation of two NASA projects under consideration that will make both in situ measurements and remote observations—Solar Probe and Interstellar Probe—the committee decided to defer to the Committee on Solar and Space Physics of the Space Studies Board. Third, in the case of the interdisciplinary field of particle astrophysics, the committee evaluated projects that use particles as tools for remote observation, but not projects that focus on the physics of the particles themselves. Finally, based on informal discussions with the Committee on Gravitational Physics of the Board on Physics and Astronomy, the committee did not evaluate possible future upgrades to the Laser Interferometer Gravitational-wave Observatory (LIGO) project. This project is discussed in the NRC report Gravitational Physics: Exploring the Structure of Space and Time (NRC, 1999). PURPOSE AND CONTENT OF THE TWO VOLUMES This astronomy and astrophysics survey includes the report of the survey committee (this volume) plus a separate volume, Astronomy and Astrophysics in the New Millennium: Panel Reports (NRC, 2001), comprising the reports of seven of the nine panels. The reports of the Panel on Astronomy Education and Policy and the Panel on Benefits to
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Astronomy and Astrophysics in the New Millennium the Nation from Astronomy and Astrophysics have been incorporated into this volume. This volume reflects the consensus of the Astronomy and Astrophysics Survey Committee; each chapter in the Panel Reports reflects the consensus of the corresponding panel. Every effort has been made to ensure that the recommendations in the two volumes are consistent; if any discrepancy between the report of the committee and a report of a panel remains, the report of the committee takes precedence. The purpose of the panel reports is to describe the new initiatives in more detail, to provide more extensive justification for the priorities, and to give additional priorities, applying typically to small projects, appropriate for individual subfields of astronomy and astrophysics. The committee’s primary recommendations for new initiatives are summarized in the remainder of the present chapter. Chapter 2 describes the scientific case underlying each recommendation. Programs already in operation or that have been recommended in previous astronomy surveys are summarized in Chapter 3, which also gives full explanations of the proposed new initiatives. Chapters 4 through 6, respectively, describe the benefits that astronomy and astrophysics provide to the nation, discuss the role of astronomy in education, and offer policy recommendations aimed at maintaining the health of the discipline and enhancing its contributions to science in general. A glossary of technical terms and a list of abbreviations and acronyms are included in an appendix to this volume. OPTIMIZING THE RETURN ON THE NATION’S INVESTMENT IN ASTRONOMY AND ASTROPHYSICS The United States has made and continues to make a significant investment in exploring the universe. In exchange, the nation deserves the maximum scientific return for this investment and widespread dissemination of the results. The astronomy and astrophysics enterprise depends on highly trained and motivated people, on technologically sophisticated facilities and missions, and on institutions properly equipped to manage them. How can this system be optimized to address the frontier scientific problems most effectively, both now and in the future?
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Astronomy and Astrophysics in the New Millennium BALANCING NEW INITIATIVES WITH THE ONGOING PROGRAM The first step in optimizing the program is to achieve a proper balance between new initiatives and the ongoing program. Congress specifically asked the committee to address this issue, and its response and discussion are given in Chapter 6. Many of the policy recommendations discussed there are directly relevant to the question of balance. The committee reaffirms the recommendations of the 1991 Astronomy and Astrophysics Survey Committee (NRC, 1991) by endorsing the completion of the Space Infrared Telescope Facility (SIRTF), the Millimeter Array (MMA; now part of the Atacama Large Millimeter Array, or ALMA), the Stratospheric Observatory for Infrared Astronomy (SOFIA), and the Astrometric Interferometry Mission (now called the Space Interferometry Mission, or SIM). Consistent with the recommendations of the Task Group on Space Astronomy and Astrophysics (NRC, 1997), the committee stresses the importance of studying the cosmic microwave background with the Microwave Anisotropy Probe (MAP) mission, the European Planck Surveyor mission, and ground-based and balloon programs. A particular attraction of SIM is its dual capability: It enables both the detection of planets through narrow-angle astrometry and the mapping of the structure of our galaxy and nearby galaxies through wideangle astrometry. It is critical that an accuracy of a few microarcseconds for wide-angle measurements be achieved in order to address a wide variety of fundamental problems throughout the decade. The committee endorses U.S. participation in the European Far Infrared Space Telescope (FIRST), which gives U.S. astronomers the chance to observe the entire far-infrared and submillimeter regions of the spectrum with no impediments from the residual atmosphere that can hinder observing from airborne platforms. The committee also endorses NASA’s decision to continue to operate the Hubble Space Telescope at a reduced cost until the end of the decade to maintain the capability for critical space-based ultraviolet and optical observations. To achieve the full scientific potential of a new facility, it is essential that, prior to construction, funds be identified for operation of the facility, for renewal of its instrumentation,
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Astronomy and Astrophysics in the New Millennium and for grants for data analysis and the development of associated theory. NASA follows the spirit of this recommendation in large part by including the costs of Mission Operations and Data Analysis (MO&DA) in budgetary planning for new missions. The wisdom of this approach is manifest in the wealth of discoveries and new interpretations published during the prime years of NASA missions. The committee recommends that funds for closely related theory be included in MO&DA as well; a specific proposal for “Theory Challenges” is outlined below. The committee further recommends that the NSF include funds for (1) operations, (2) facility instruments and other capabilities that enable full exploitation of the new facility, and (3) grants for the ground-breaking research—both observational and theoretical—enabled by the new facility during its early, highly productive years. These recommendations are consistent with those of the 1991 survey. Based on the experience with several recently completed facilities, the committee has budgeted operations at 7 percent of the capital cost per year and instrumentation at 3 percent per year for the first 5 years of operation (see Chapter 6); the actual percentages should be based on the particular circumstances of the individual facility. To enable observers and theorists to explore and develop the full capabilities of new facilities, the committee recommends budgeting “facility grants” for research associated with major facilities at about 3 percent of the capital cost per year for the first 5 years. A cost-effective and competitive grants program for moderate facilities requires a somewhat higher percentage, and the committee recommends that facility grants for such facilities be budgeted at about 5 percent per year. No facility grants are recommended for small projects since the funds available would be too small. Funds for operations, instrumentation, and facility grants for a period of 5 years are included in the committee’s cost estimates for most ground-based initiatives (see the section below, “Proposed Priorities for Ground- and Space-Based Initiatives”). Adequate funding for unrestricted grants that provide broad support for research, students, and postdoctoral associates is required to ensure the future vitality of the field; therefore new initiatives should not be undertaken at the expense of the unrestricted grants program. A strong grants program is critical both to realize the full science value from state-of-the-art facilities and to ensure the future health of the
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Astronomy and Astrophysics in the New Millennium field. On the basis of the NASA experience, the committee believes that grants associated with new ground-based facilities, as proposed above, should address the data analysis and science needs for those facilities as well. Such grants should also support some postdoctoral associates and graduate students. However, past experience shows that it is often the individual investigator grants that are not tied to a specific facility or program—the unrestricted grants—that support the innovative new research that drives the future directions of astronomy. Previous decadal astronomy surveys have also emphasized the importance of unrestricted grants in advancing the field. STRENGTHENING GROUND-BASED ASTRONOMY AND ASTROPHYSICS The United States is fortunate to enjoy substantial state and private funding for ground-based optical and infrared facilities and, to a lesser extent, radio and solar facilities. To optimize the return on federal investment in ground-based astronomy, the committee recommends that: U.S. ground-based optical and infrared facilities, radio facilities, and solar facilities should each be viewed by the National Science Foundation and the astronomical community as a single integrated system drawing on both federal and nonfederal funding sources. The NSF must draw on the strengths of the independent observatories to achieve its goals in ground-based astronomy. Independent observations are playing their appropriate roles effectively in both radio and solar astronomy, but less so in optical and infrared astronomy. Several of the committee’s recommendations should help to build the partnership between federal and independent observatories in both radio astronomy (the Combined Array for Research in Millimeter-wave Astronomy and the Square Kilometer Array technology development) and optical and infrared astronomy (the Telescope System Instrumentation Program). Effective national organizations are essential to coordinate, and to ensure the success and efficiency of, these systems. These national organizations should work with the universities and independent observatories in developing the next generation of telescopes. The National Radio Astronomy Observatory (NRAO) and the
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Astronomy and Astrophysics in the New Millennium National Astronomy and Ionosphere Center (NAIC) currently fulfill the committee’s recommended role for radio astronomy, and the National Solar Observatory (NSO) does so for the solar physics community. The National Optical Astronomy Observatories (NOAO) as currently functioning and overseen does not fulfill this role for the community of ground-based optical and infrared observers. A plan for the transition of this organization should be developed, and a high-level external review, using appropriate criteria, should be initiated (see Chapter 6). As part of the effort to develop effective systems of telescope facilities, universities and independent observatories should work with the national organizations to develop coherent strategic plans for each system (optical, solar, and radio) and to develop those facilities that are too large or expensive to fit within the resources of a single institution or consortium. Universities should assume the responsibility for purchasing, instrumenting, and operating small telescopes needed for their students and faculty. Optimizing the overall program also requires a mechanism to achieve the correct balance among existing facilities to address the important scientific problems as they evolve. Cross-disciplinary competitive reviews should be held about every 5 years for all NSF astronomy facilities. In these reviews, it should be standard policy to set priorities and consider possible closure or privatization. New facilities should undergo their first competitive review between 5 and 10 years after they become operational. NASA holds a senior review of its MO&DA programs every 2 or 3 years; the greater frequency is appropriate in view of the shorter lifetime of space missions. The recommended 5-year reviews should provide input to NSF’s Division of Astronomical Sciences (AST), enabling it to adjust its entire portfolio to meet changing scientific priorities and to satisfy its strategic plan. The Department of Energy (DOE) supports a broad range of programs in particle and nuclear astrophysics and in cosmology. Such investigations probe the fundamental forces and the nature of matter in ways that directly complement accelerator-based experiments and basic theoretical research. DOE research in plasma physics also has many synergies with astrophysics. The scientific payoff of these programs
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Astronomy and Astrophysics in the New Millennium telescopes in the United States. The top priority for moderate projects for the new decade is TSIP, an NSF program that will maximize the scientific effectiveness of these telescopes by instrumenting them and by making them accessible to the entire astronomical community. It will have a multiplier effect by encouraging the continuation of substantial nonfederal investments, while at the same time helping to bring the national and private observatories together as a coherent research system. Under this initiative, the NSF would fund the construction of peer-reviewed new instrumentation at private observatories in exchange for telescope time or other equally valuable benefits for the community at large. The value of the observing time (determined from the cost of operations and the amortized investment) should be 50 percent of the granted funds. Gamma-ray Large Area Space Telescope. GLAST, the second priority for moderate projects, is a powerful gamma-ray telescope with a sensitivity 30 times greater than that of its predecessor, the Energetic Gamma Ray Experiment (EGRET) instrument on the Compton Gamma Ray Observatory. GLAST will study powerful jets from the supermassive black holes in the centers of distant galaxies, the acceleration mechanisms of cosmic rays, and the origin of tremendous bursts of gamma-ray radiation from the distant universe. GLAST has the potential for breakthrough discoveries, such as by observing gamma rays from dark matter annihilation. It will detect gamma rays in the photon energy range between 10 MeV and 300 GeV with unprecedented positional accuracy. The committee applauds the crucial technical contributions of DOE to this important NASA mission. Laser Interferometer Space Antenna. LISA is unique among the recommended new initiatives in that it is designed to detect the gravitational radiation predicted by Einstein’s theory of general relativity. The direct measurement of gravitational radiation from astrophysical sources will open a new window onto the universe and enable investigations of the physics of strong gravitational fields. LISA consists of three spacecraft spaced 5 million km apart in an equilateral triangle, with lasers accurately monitoring their separation. It will be sensitive to gravitational-wave frequencies between 10−1 to 10−4 Hz, frequencies too low to be detected by the ground-based LIGO. For the first time, it will be possible to observe evidence of the coalescence of supermassive black holes as distant galaxies merge, and the gravitational radiation from white dwarf
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Astronomy and Astrophysics in the New Millennium binaries in our own galaxy. It is assumed that LISA will be a joint mission between NASA and ESA, with costs shared approximately equally. Advanced Solar Telescope. AST will observe solar plasma processes and magnetic fields with unprecedented resolution in space and time. It will provide critical information needed to solve the mysteries associated with the generation, structure, and dynamics of the surface magnetic fields, which govern the solar wind, solar flares, and short-term solar variability. AST is a ground-based, 4-m-class, adaptive-optics-equipped facility that will operate in the wavelength band from 0.3 to 35 µm. It is proposed as a joint project with international partners, in which the United States would provide about half the costs. Square Kilometer Array Technology Development. The SKA is an international ground-based centimeter-wave radio telescope array with 106 square meters of collecting area that will enable study of the first structures and the first luminous objects to form during the dawn of the modern universe, and will provide unprecedented images of protostellar disks and the neutral jets launched by young stars. SKA’s sensitivity will be a factor of 100 greater than that of existing centimeter-wave facilities. The increase in sensitivity has great discovery potential, and SKA will revolutionize the study of objects and phenomena that are currently undetectable at centimeter wavelengths. The U.S. SKA development program will, in collaboration with the international radio astronomy community, aggressively pursue technology and technique development in this decade that will enable the construction of the SKA in the following decade. Solar Dynamics Observatory. SDO will probe the outer layers of the Sun to determine the connections between the interior dynamics and the activity of the solar corona, the origin of sunspots and solar active regions, and the origin of coronal mass ejections and solar flares. SDO is a space-based mission that will carry a number of instruments and small telescopes to monitor the Sun continuously at ultraviolet and optical wavelengths (0.02 to 1 µm). Combined Array for Research in Millimeter-wave Astronomy. CARMA is the planned combination of the Berkeley-Illinois-Maryland Association (BIMA) and the Owens Valley Radio Observatory (OVRO) millimeterwave arrays at a superior site along with the addition of new, smaller
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Astronomy and Astrophysics in the New Millennium antennas. The resulting hybrid array will have unique imaging qualities, sensitive to both small and large scales. It will study star formation at all epochs, and it will measure the small distortions in the cosmic (Big Bang) microwave background caused by the hot gas in distant clusters of galaxies along the line of sight. Its Northern Hemisphere location will provide sky coverage complementary to ALMA. Of the construction costs, 60 percent will come from nonfederal sources. Energetic X-ray Imaging Survey Telescope. EXIST will survey the entire sky every 90 minutes to search for weak and often time-variable astronomical sources of 5- to 600-keV x-ray photons. Such x rays emanate from many sources, including supermassive black holes in the centers of galaxies, stellar mass black holes, neutron stars, and embedded supernovae in our galaxy, and the mysterious distant sources of gamma-ray bursts of radiation. Attached to the International Space Station, EXIST will survey sources 1,000 times weaker than the sources in the previous hard x-ray survey by the High Energy Astronomical Observatory (HEAO-1). EXIST’s repeated surveys of the entire sky in the hard x-ray region will complement those by LSST at optical wavelengths. Very Energetic Radiation Imaging Telescope Array System. VERITAS will perform the first sensitive sky survey for astronomical sources of extremely energetic photons—those with energies from 100 to 10,000 GeV. VERITAS will complement GLAST and EXIST in studying the cosmic sources of relativistic particles such as supermassive black holes, gammaray burst sources, pulsars, and supernova remnants. Making use of the established technology of the 10-m reflector at the Whipple Observatory, VERITAS consists of an array of seven 10-m-diameter reflectors that will achieve more than an order-of-magnitude improvement in sensitivity and have a far greater ability than existing instruments to locate sources. Advanced Radio Interferometry between Space and Earth. ARISE is a sensitive, Earth-orbiting radio antenna with a diameter of about 25 m that will improve the angular resolution of the ground-based Very Long Baseline Array by a factor 6. It will probe the regions near supermassive black holes, which are thought to produce relativistic jets, and will enable the study of maser sources, both in the Milky Way and in the nuclei of other galaxies.
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Astronomy and Astrophysics in the New Millennium Frequency Agile Solar Radio Telescope. Radio waves from the Sun bring information about the heating of the corona, the nature and evolution of coronal magnetic fields, the structure of the solar atmosphere, and the origin of the solar wind. FASR will analyze this radiation over a frequency range from 0.3 to 30 GHz, and it will improve on existing facilities by operating at hundreds of frequencies and providing a factor-of-10 better spatial resolution. South Pole Submillimeter-wave Telescope. The SPST will take advantage of the superb atmospheric transmission conditions between wavelengths of 200 µm and 1 mm at the South Pole to survey the dusty universe, study small variations in the background radiation emanating from the early pregalactic universe, and identify primordial galaxies. OTHER PROJECTS Two areas in which the committee considered it premature to set priorities are cosmic microwave background experiments and particle astrophysics. In both disciplines, projects are often experiments rather than observatories. As a result, it is difficult to plan far in advance, since the best strategy may depend critically on the outcome of ongoing experiments. Observations of the cosmic microwave background can determine the large-scale properties of the universe and reveal the tiny fluctuations that were the seeds of all the structure we see today. These observations are of fundamental importance to both astronomy and physics. Together with ground-based and balloon experiments, NASA’s MAP mission, to be launched in spring 2001, will revolutionize knowledge of the microwave background, and the committee believes that no decision on the next major or moderate microwave background project should be made until the results from that mission are available. ESA’s Planck mission later in the decade will also provide important information, but it will be possible to decide on the next step before its results are available. Together, MAP and Planck will test the most promising ideas about the very early universe as well as determine cosmological parameters to high precision. The next frontier is to measure the polarization of the cosmic microwave background, which has the potential of probing even earlier times, close to the Big Bang itself. Particle astrophysicists view the universe through different eyes than
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Astronomy and Astrophysics in the New Millennium do most astronomers: Instead of photons, they observe energetic particles, and they search for exotic new particles that could account for the dark matter. The committee decided that it was too early to prioritize the Northern Hemisphere Auger project or Telescope Array for ultrahigh-energy cosmic rays and the Ice Cube experiment for high-energy neutrinos. In each case, ongoing experiments—the Southern Hemisphere Pierre Auger Observatory project and the Antarctic Muon and Neutrino Detector Array (AMANDA) experiment at the South Pole—will provide critical information that will enable an informed decision to be made soon. The decision on how to pursue future searches for dark matter will be guided by the outcome of experiments now just starting. SMALL INITIATIVES National Virtual Observatory. The NVO is the committee’s top-priority small initiative. NVO involves the integration of all major astronomical data archives into a digital database stored on a network of computers, the provision of advanced data exploration services for the astronomical community, and the development of data standards and tools for data mining. It will create a powerful resource for public education and outreach by making near-real-time observations accessible over the Internet. NVO will enable professional astronomers, educators, and the public to take full advantage of the wealth of data from existing and planned surveys such as LSST. NVO is made possible by huge advances in the past decade in computer speed, widespread access to high-speed networks, a dramatic decrease in the cost of computing and data storage capabilities, and an ongoing revolution in techniques to extract science from a large data set. The committee recommends coordinated support from both NASA and the NSF, since NVO will serve both the space- and ground-based science communities. Additional Small Intiatives. The remaining recommendations for small initiatives are listed alphabetically and are not prioritized, but they represent a number of exciting opportunities for making a relatively small investment to potentially achieve a major gain in capability and scientific return. Several of these opportunities span both space- and ground-based astronomy, like NVO. To facilitate the interpretation of the tremendous harvest of data throughout the decade, the committee recommends (1) augmentation of NASA’s Astrophysics Theory Program and (2) initiation of a NASA- and NSF-funded National Astrophysical
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Astronomy and Astrophysics in the New Millennium Theory Postdoctoral Program that would award 10 portable 3-year postdoctoral positions each year. In view of the tremendous increase in the volume and complexity of the spectroscopic data to be gathered across the electromagnetic spectrum by new facilities over the course of the decade, the committee recommends the establishment of a Laboratory Astrophysics Program funded by both NASA and the NSF. The Ultralong-Duration Balloon (ULDB) program offers the prospect of carrying payloads that weigh several tons to roughly 40-km altitudes for flights that last several months. For certain types of experiments, this program offers an alternative to small space experiments at a fraction of their cost. The committee recommends an augmentation of the ULDB program for the development of a steering capability that would increase both the duration and the probability of success of the balloon flights. The Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS) will measure the spectrum and composition of cosmic rays with energies up to 1,000 TeV. This experiment will provide unique data for studying the origin of cosmic rays and the mechanism by which they are accelerated. The Low Frequency Array (LOFAR), a joint project now under way between the Netherlands Foundation for Research in Astronomy and the U.S. Naval Research Laboratory, provides a 100- to 1,000-fold improvement in sensitivity and resolution over existing radio telescopes in the wavelength range from 2 to 20 m. It has the potential to discover the hydrogen clouds out of which the first galaxies formed. The committee recommends that the NSF contribute to LOFAR so that it will be available to the entire astronomical community. Expansion of the Synoptic Optical Long-term Investigation of the Sun (SOLIS) from one station to a three-station network would permit continuous, 24-hour monitoring of magnetic fields on the solar surface. An expanded SOLIS promises crucial data for understanding the magnetic origin of solar variability and a far greater capability to forecast the space weather that so adversely affects space satellites. TECHNOLOGY Technological innovation has often enabled astronomical discovery. Most of the major discoveries listed at the beginning of this chapter were possible only because of the remarkable advances in technology in the past two decades. Continued investment in technology in this decade is required for many of the initiatives recommended in this report: For example, GSMT and AST require advances in adaptive optics, and TPF
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Astronomy and Astrophysics in the New Millennium requires the development of space interferometry. For the space-based initiatives, technology investment as specified in the existing NASA technology road map is an assumed prerequisite for the cost estimates in Table 1.1. It is essential to maintain funding for the planned technology development if NASA is to keep these missions on schedule and within budget. Targeted technology programs involving a joint effort between engineers and scientists will be essential to success in these projects. As noted above, the committee endorses NASA’s policy of completing the technological development of a mission prior to starting it. The NSF is applying a similar approach the design and development of ALMA, a policy the committee endorses. Longer-range investments in technology in this decade are needed to enable the major projects in the next decade—and to make them more cost-effective. Space-based projects that could be started in the decade 2010 to 2020 include a large 8-m-class ultraviolet telescope, a far-infrared interferometer, an x-ray interferometer, and an x-ray telescope with an effective area of 100 square meters. The best-defined ground-based project for the decade 2010 to 2020 is the Square Kilometer Array, for which the committee has recommended technology development. Other possible ground-based projects for that decade include the next step beyond GSMT in optical telescopes and large interferometers that operate at infrared wavelengths. To make these projects feasible in the decade 2010 to 2020, the committee recommends investing in the technologies listed in Table 1.3; priorities for these technologies have not been established. For ground-based astronomy, the committee recommends development of very large, high-speed digital correlators for radio astronomy; infrared interferometry; and specialized dark-matter detectors. Space-based astronomy requires investments in spacecraft communication to enable high rates of data transmission from distant telescopes to ground-based stations. The estimated cost for the development of a suitable radio transmitter is listed in Table 1.3. In addition, the committee suggests that NASA consider establishing an optical communications link at “L2,” the proposed site for NGST and other future NASA missions. The committee recommends investing in the development of x-ray interferometry, which has the potential of actually imaging the event horizon of a black hole, and in technology for the next generation of space observatories: energy-resolving array detectors for optical, ultraviolet, and x-ray wavelengths; far-infrared array detectors; refrigerators to maintain the cryogenic temperatures needed by these detectors; large, lightweight optics (some-
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Astronomy and Astrophysics in the New Millennium TABLE 1.3 Technology Development for Future Initiatives and Estimated Costs Technology Initiative Decade Cost ($M) Ground-based Megacorrelators 10 Infrared interferometry 40 Dark matter detectors 12 Subtotal for ground-based technology 62 Space-based Spacecraft communication 70 X-ray interferometry 60 Technology for next-generation observatories: Energy-resolving array detectors 40 Far-infrared array detectors 10 Refrigerators for space experiments 50 Large, lightweight optics 80 MeV detector technology 10 Subtotal for space-based technology 320 TOTAL 382 times referred to as “gossamer optics”) for infrared, optical, ultraviolet, and x-ray wavelengths; and sensitive gamma-ray (MeV) detectors. These proposed technology developments are discussed in greater detail in the Panel Reports (NRC, 2001). ASTRONOMY’S ROLE IN EDUCATION Astronomers have a vital role to play in contributing to the development of science education in the United States. Among scientists, astronomers make a disproportionately large contribution to the improvement of public science literacy relative to the comparatively small size of the astronomical community because of the broad appeal of astronomical concepts and ideas. Astronomy resonates with some of the most basic questions of humanity: When did the universe begin? How has it evolved? What will be its ultimate fate? Is there life elsewhere?
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Astronomy and Astrophysics in the New Millennium How will the universe around us affect the development and continued existence of the human species? Astronomy provides a gateway for increased public understanding of humanity’s place in the universe and of the nature of science. Each year 28 million visits are made to planetariums in the United States. More than 200,000 college students take an astronomy course each year. Thus, roughly 10 percent of all U.S. college students will take an astronomy course before they graduate, and for many of these astronomy will be the only science course they ever take. Astronomy is heavily covered by the media, has attracted millions of people on the Web, and enjoys the support of hundreds of thousands of amateur astronomers. The committee recognizes the tremendous importance of improving the scientific literacy of the nation. Recommendations to enhance astronomy’s role in education are discussed in Chapter 5. The key recommendations are as follows: The engagement of astronomers in outreach to the K-12 community should be expanded and improved by ensuring (1) appropriate incentives for their involvement; (2) training and coordination for effective and high-leverage impact; (3) careful scrutiny of major initiatives and widespread dissemination of information regarding their successes and failures; and (4) recognition of the value of this work by the scientific community. More universities with both astronomy and education departments should establish pilot partnerships to bring scientists, educators, and experienced teachers together to design exemplary astronomy-based science courses for preservice teachers, with the goal of contributing to the achievement of long-term systemic reform in K-12 science education. Federal agencies charged with increasing the contribution of professional scientists to educational initiatives should work with astronomers and educators to develop a common set of goals, pathways to achieve them, and mutually accepted standards for measuring success.
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Astronomy and Astrophysics in the New Millennium NSF should invest additional resources in improving public recognition of the achievements of all NSF-funded facilities and projects. Astronomy, with its wide public appeal, could provide a starting point. Achieving better recognition for NSF-sponsored successes would require that a stronger interface be established between the media and the NSF through the efforts of dedicated press officers. The NSF also should develop a stronger presence on the Internet. NSF centers and facilities should develop informative Web pages, maintain state-of-the-art visitors centers, and expand outreach into the local communities. NOTES 1. Panel members are listed in the front matter. 2. Catherine Cesarsky, DSM Orme des Merisiers, now Director General, European Southern Observatory; Edward van den Heuvel, University of Amsterdam; Don Morton, Herzberg Institute of Astrophysics, National Research Council of Canada; Luis Rodriguez, Instituto de Astronomiá, National Autonomous University of Mexico; Yasuo Tanaka, Institute of Space and Astronautical Sciences, Japan, and Max-Planck-Institut für extraterrestrische Physik; Reinhard Genzel, Max-Planck-Institut für extraterrestrische Physik; Sami Solanki, ETH Zürich Institute of Astronomy, Switzerland; and Roger Davies, Durham University, United Kingdom.
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Representative terms from entire chapter: