Astronomy and Astrophysics for the 1980's, Volume 2 Reports of the Panels (1983) / Chapter Skim
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III. Science Opportunities in the 1980's
III. Science Opportunities in the 1980's
Pages 119-134
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From page 119... ...
Solar Nonradial Pulsations and Seismology The unexpected discovery that the solar atmosphere has radial wave motions with a 5-min period led to major theoretical studies of the generation, propagation, and damping of acoustic, gravity, and magnetic waves in stellar atmospheres. Theory indicates that the oscillations observed at the solar surface are manifestations of standing, nonracial p-mode oscillations of the outer convection zone and predicts a well-defined observable relation between the temporal and spatial power spectra of the 5-min oscillations.
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From page 120... ...
The Very Large Array (VLA) radio telescope, constructed in stages over the past decade, is now becoming fully operational; two new 4-m optical telescopes have gone into operation at Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory; and Space Telescope (ST)
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From page 121... ...
During the coming decade, the variety of approaches available for the detailed study of our Galaxy should produce a more coherent picture of the stellar system in which we live. Utilizing observations from ST and the recommended 15-m facility, dynamical studies of faint halo stars, distant globular clusters, and outlying satellite galaxies will delineate the extent and the mass of the Galactic system; spectroscopic studies will determine chemical evolution as a function of age and of position; and radio, millimeter, and submillimeter observations of molecular clouds will identify regions of star formation and help us to learn their histories and dynamics.
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From page 122... ...
For dwarfs, giants, and globular clusters, a detailed map of the halo, complete with distances, composition, abundances, and space motions will be forthcoming and will be the ultimate test of models of halo formation and the possible presence of nonluminous matter in the outer regions of our Galaxy. m e composition of the inner spheroidal bulge; star-bystar studies of the nuclear bulge; and details of the physics, chemistry, and dynamics of interstellar molecules in the Galactic nucleus will also emerge from observations in the optical, W
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From page 123... ...
It now appears that the two major components are a hot intercloud medium and the dense molecular clouds discussed above. Observations of diffuse soft x rays made with rockets and with HEAD-1 and observations of W absorption lines made with Copernicus demonstrate that a substantial fraction of the local interstellar medium is filled with hot (T = 10V K)
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From page 124... ...
The degree of "patchiness" of the halo gas will be determined. All of this information is relevant to the absorption lines seen in quasar spectra, because the likelihood of seeing absorption lines through halos of foreground galaxies depends on these same properties in galaxies along the lines of sight to the quasars.
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From page 125... ...
Are the outer atmospheres of most stars heated by wave processes, the dissipation of magnetic fields of magnetohydrodynamic waves, or radiative instabilities? Also, why do the cool luminous stars appear not to have hot coronas?
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From page 126... ...
Major photometric programs aimed at detecting faint halo stars must be pursued, as well as new dynamical tests for unseen matter. Important facilities here include the 21-cm capability of VLA, as well as improved optical techniques involving multiplexing red-shift detectors, additional 3- to 5-m-class telescopes, larger optical telescopes,
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From page 127... ...
b. Quasars The fundamental problems for the 1980's are the structure of the central energy source in quasars and active galactic nuclei and the physical processes involved in the energy release.
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From page 128... ...
Direct observational evidence on the nature of the central energy source at high spatial resolution can currently be obtained only with VLBI observations. Because of its much shorter working wavelength, optical interferometry offers significant potential gains over radio techniques for receivers operating on identical baselines.
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From page 129... ...
The Cosmic Background Explorer (COBE) satellite will provide excellent measurements of the spectrum and of the large scale anisotropy (angular scales of about 5 deg or more)
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From page 130... ...
To augment existing astrometric programs and provide more uniform coverage, an astrometric instrument (2-m class) will be required in the southern hemisphere, and improved detectors (focal-plane detectors and interferometers, for example)
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From page 131... ...
The fundamental properties of the solar core, in particular its rotation rate, chemical composition, temperature distribution, and details of the processes of nuclear energy generation.
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From page 132... ...
(c) The processes involving small-scale velocity and magnetic fields and the wave modes that determine the thermodynamic structure and dynamics of the solar photosphere, chromosphere, and corona and their implications for stellar atmospheres.
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From page 133... ...
Research in the 1980's should extend current work and, most importantly, initiate fundamental new treaments of the problem, such as detailed studies of the effects of magnetic fields on the dissipation of all possible wave modes. Recent measurements by OS0-8 indicate that acoustic waves generated in the solar convection zone carry insufficient energy to heat the corona.
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From page 134... ...
(f) The structure and plasma dynamics of the solar corona, including the processes involved in heating various coronal structures and initiating the solar wind; the origin of coronal transients; the three-dimensional structure of the interplanetary medium and its implications for cosmic-ray modulation; and the implications for stellar coronas and winds and other astrophysical flows e Two outstanding discoveries of solar physics during the past decade are (1)
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