Particle and nuclear astrophysics and gravitational-wave astronomy offer tremendous discovery potential in the next decade and beyond. The direct measurement of gravitational waves from astrophysical sources will open new investigations in both astrophysics and the physics of strong gravitational fields. High-energy charged particles and gamma rays as well as neutrinos carry unique information about the high-energy universe that is complementary to information obtained by more traditional astronomical approaches. The quest to identify the dark matter is of the utmost importance for astrophysics and cosmology as well as for elementary particle physics.
The Panel on Particle, Nuclear, and Gravitational-Wave Astrophysics of the Astronomy and Astrophysics Survey Committee recommends that highest priority be given to the Laser Interferometer Space Antenna (LISA) because of the fundamental and novel exploration of the gravitational-wave universe it can accomplish, including the observation of massive black holes coalescing in colliding galaxies and the study of white dwarf binaries in our own galaxy. The panel’s highest recommendation among ground-based projects (and second overall) is the Very Energetic Radiation Imaging Telescope Array System (VERITAS), which together with the Gamma-ray Large Area Space Telescope (GLAST) will study many rapidly variable energetic sources, including nuclei of active galaxies, and will map the gamma-ray sky with unprecedented precision. An attractive small-scale opportunity is the Advanced Cosmic-ray Composition Explorer for the Space Station (ACCESS), which will be able to measure directly the spectrum of particles to 1000 TeV and for the first time to distinguish the spectrum produced by the cosmic accelerators from energy-dependent effects of propagation in the Galaxy.
In setting priorities, the panel used three criteria: scientific importance, technological readiness, and budgetary reality. In some cases, however, where the path forward depends on results of investigations just now starting, it is not yet possible to evaluate a project even though it addresses an extremely important problem and is likely to be ready within the coming decade. The panel therefore recommends a broad program of particle astrophysics building on the important new initiatives of the past decade, including solar neutrino observatories, giant air shower detectors, neutrino telescopes, and searches for dark matter.
The scientific interest and importance of all the projects of this panel