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General relativity also predicts the existence of gravitational waves, which travel at the speed of light. Our understanding of gravity waves has improved recently to include solving the relevant equations when gravity is strong, thanks to theoretical breakthroughs in numerical relativity. Astrophysicists now have the ability, in principle, to calculate the complete waveforms that should be observed from most types of powerful sources. To date, the effects of gravitational radiation have been observed only indirectly using sensitive measurements of spinning magnetized neutron stars, or pulsars, when they have orbiting stellar companions. These measurements are consistent with the theory, but the goal of detecting gravitational waves directly has not yet been met. The first of these ripples in space-time likely to be detected will probably arise from the death spiral of a binary neutron star. Sustained international investments over the last 20 years would culminate with the mid-decade completion of the advanced Laser Interferometer Gravitational Wave Observatory (LIGO), which should make regular detections of this and many other types of sources at relatively short wavelengths. However, the ultimate goal is to measure the full gravitational waveform for direct comparison with theoretical expectations. To accomplish this, measurements are needed at longer wavelengths to test the theory by means of sustained observations of merging black holes. This is the primary purpose of LISA, from which the signals will be of such high quality that the full gravitational waveform can be measured. A key recent development has been the solution of the theoretical problem of calculating the signals that should be seen from merging black holes. The results will test current understanding of general relativity and provide accurate measurements of the spin and mass of the merging black holes. These are vital parameters for understanding the origins and growth of the most massive black holes in the universe. We should also witness the capture of stars by massive black holes with signals of such long duration and fidelity that the space-time of the black hole can be directly mapped. In summary, this survey recommends supplementing our current ability to use the universe as a giant cosmic laboratory to study dark energy, inflation, and black holes. Success in this endeavor would provide critical constraints on the laws of physics and the behavior of the universe that would inform efforts to realize a unification of gravity and quantum mechanics through string theory or other approaches; see Box 7-3. THE LARGER SCIENCE PROGRAM The three primary science objectives motivated the difficult prioritization choices the committee had to make. They represent goals against which progress and prospects for individual facilities can be assessed over the coming decade. However, there is much other science outlined in Chapter 2 that is also important and timely. The proposed activity program of Astro2010 also advances this larger research program, cast here as in Chapter 2 in terms of cross-cutting themes in astronomy and astrophysics research. Einstein Program Advisory Committee. While it would address important science goals, the high estimated cost of $2.4 billion, well over 10 times the cost indicated in the preceding AANM decadal survey report, ruled it out for further consideration, and it is no longer recommended. PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION 7-12
Box 7.3 Implementing the Physics of the Universe Science Plan . • Continue theoretical investigations of models of dark energy and inflation. • Combine observations with LSST, WFIRST, and GSMT to measure nearby distant supernova explosions and map the expansion of the universe. • Use WFIRST and LSST to find traces of the residual sound waves produced in the first moments of the universe by mapping the distribution of galaxies and making an independent measurement of the rate of expansion of the universe. • Measure the shape distortions of distant galaxies caused by weak gravitational lensing, using WFIRST and LSST to help characterize the properties of dark energy. • Find and study distant clusters of galaxies to measure the rate of growth of structure in the universe using IXO and microwave background observations. • Complete the theoretical calculations of waveforms from merging black holes. • Detect bursts of gravitational radiation from merging black holes using LISA. • Study the epoch of inflation by measuring the imprint of gravitational radiation on the cosmic microwave background. • Observe X‐rays from gas orbiting close to the event horizon of black holes using IXO and relativistic jets produced by black holes using ACTA. • Gather indirect evidence using ACTA to show that dark matter comprises a new type of elementary particle by detecting the gamma rays it may emit. Discovery Anticipating research results in a rapidly changing field is demonstrably hard, and comparisons between expectations and actual scientific results are both humbling and exhilarating. For example, when the Keck Observatory, the Hubble Space Telescope, and the Spitzer Space Telescope were designed astronomers had no evidence that there were planets around nearby stars or that gamma-ray bursts were at cosmological distances. These observatories, both independently and when used together to study the same objects, have been invaluable in advancing knowledge in unpredictable directions. Astronomy is still as much based on discovery as it is on predetermined measurements. The committee emphasizes that its recommended activities have the capacity to find the unexpected and the versatility to engage in follow-up observations. For example, WFIRST and LSST as recommended here would open up the time domain to reveal remarkable surprises and enable the creation of massive databases that will be mined for decades. It would be unprecedented in the history of astronomy if the gravitational radiation window being opened up by LISA does not reveal new, enigmatic sources. Most of the observing time on GSMT, IXO, and ACTA would not be allocated according to a preordained strategy; rather, individuals and teams would compete for time to explore new scientific approaches and pursue recent discoveries. The broadly based and balanced suite of facilities that are recommended is flexible and resilient enough to make and exploit the many unanticipated and thrilling discoveries that are sure to come during the coming decade. Many of the most fundamental advances in astronomy and astrophysics have resulted from theoretical discoveries that could not have been anticipated in any planning exercise—the theory of inflation is one example⎯but the recommended Theoretical and Computational Network program and augmentations in individual investigator grants programs at NSF and NASA will help to enable such discoveries. PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION 7-13
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PREPUBLICATION COPY
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THE NATIONAL ACADEMIES PRESS 500 Fi
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COMMITTEE FOR A DECADAL SURVEY OF A
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Panel on Stars and Stellar Evolutio
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DOUGLAS FINKBEINER, Harvard Univers
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SPACE STUDIES BOARD CHARLES F. KENN
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activities 2 that have emerged from
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In addition to the 27 panel meeting
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Acknowledgment of Reviewers This re
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The Accelerating Universe 2-26 The
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APPENDIXES A Summary of Science Fro
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light up the universe, marking the
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RECOMMENDED PROGRAM Maintaining a b
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TABLE ES.4 Space: Recommended Activ
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Cosmic Dawn: Searching for the Firs
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this imprint would both probe funda
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important outcome will be to open u
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estimated to be on the order of $20
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observatories. For NASA an annual b
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surveys of large fields, enabling s
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RECOMMENDATION: U.S. investors in a
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departments and the community as a
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dominate spending; (2) private-publ
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us was certainly evident during the
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BOX 2-1 Other Worlds Around Other S
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FIGURE 2‐2 The source 3C 75, show
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FIGURE 2‐3 Numerical simulation o
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FIGURE 2‐4 Left panel: Image of t
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FIGURE 2‐6 Top: Schematic of the
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Most stars with masses smaller than
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BOX 2-2 The Origin of Planets After
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send material raining into the cent
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BOX 2-4 Lifecycles in Galaxies One
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Stars Stars are the most observable
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ubiquitous high-energy charged-part
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The Nature of Inflation As describe
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FIGURE 2‐11 Pie chart showing the
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An important clue to the nature of
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Studying the properties of neutron
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FIGURE 2‐14 A possible pathway is
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partners and makes recommendations
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As astronomy research has blossomed
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are increasingly relevant. The Euro
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TABLE 3-1 Currently Operating OIR F
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29% 1990 44% US Priv US Fed Other E
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CONCLUSION: Complex and high-cost f
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Space Observatories The Laser Inter
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Physics Division (PHY); the Mathema
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4 Astronomy in Society Astronomy of
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FIGURE 4‐2 The dust sculptures of
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FIGURE 4‐5 President Obama takes
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Astronomy Inspires in the Classroom
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teaching the scientific method. The
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where the fraction of astronomers h
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Percentage of AAS Membership by Fie
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0.4 0.3 0.2 0.1 PL SO IM AG SF IN S
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FIGURE 4‐12 Number (top panel) an
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Professional training needs to acco
Page 121: assistant and associate professor p
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Page 126 and 127: THEORY Emerging Trends in Theoretic
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Page 130 and 131: TABLE 5‐2 Support for astrophysic
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Page 134 and 135: FIGURE 5‐7 Highly cited HST publi
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Page 138 and 139: FIGURE 5‐8 Number of PhDs per yea
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Page 163 and 164: FIGURE 7.1 Survey time line showing
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Page 209 and 210: PLANETARY SYSTEMS AND STAR FORMATIO
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CFP CHIPSat CIP CGRO CMB CMU CoBRA
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NRC NSB NSF NSF-AGS NSF-ARC NSF-AST
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