In addition to these two international collaborations, American physicists are involved in the development of a sophisticated experiment, Borexino, which will also be installed in Gran Sasso and will probe intermediate-energy solar neutrinos. This field of neutrino astronomy came of age in 1987 with the detection of the neutrinos from a supernova in three detectors across the world. This observation spectacularly confirmed our theoretical understanding of stellar collapse and the role played by the neutrinos in the process. Should a supernova occur in our galaxy during the operation of the solar neutrino detectors soon coming on line, important information will be obtained on the mass of the muon and tau neutrinos. Finally, recent detection by the Fly's Eye detector in Utah of an event with energy in excess of 1011 GeV gives a new incentive to develop detectors that can greatly improve the sensitivity to these fascinating high-energy events, some of which may originate outside our galaxy.
Particle astrophysics addresses issues that bear on the whole field of particle physics.
It is reasonable to anticipate that the number of particle physicists working in this field will grow during the coming decade and that the devices for further advancing this basic field will also grow in size and cost, estimated to be in the range of several tens of millions of dollars for some of the facilities discussed above. Strong collaboration among relevant U.S. funding agencies, such as the Department of Energy, the National Science Foundation and the National Aeronautics and Space Administration, will be important for the future of this field.