Astronomy and Astrophysics for the 1980's, Volume 1 Report of the Astronomy Survey Committee (1982) / Chapter Skim
Currently Skimming:
1 INTRODUCTION
1 INTRODUCTION
Pages 3-12
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 3... ...
Through modern astronomy, we now know that we are connected to distant space and time not only by our imagination but also through a common cosmic heritage: the chemical elements that make up our bodies were created billions of years ago in the hot interiors of remote and long-vanished stars. Their hydrogen and helium fuel finally spent, these giant stars met death in cataclysmic supernova explosions, scattering afar the atoms of heavy elements synthesized deep within their cores.
|
From page 4... ...
The 1960's saw the discovery of quasars, x-ray sources outside the solar system, the cosmic microwave background radiation, pulsars, high-energy celestial gamma rays, large-scale inhomogeneities in the solar corona, and polyatomic molecules in interstellar clouds. The rapid pace of discovery continued in the 1970's: 1970: Uhuru, the first satellite x-ray observatory, is launched; it reveals that many bright Galactic x-ray sources are neutron stars accreting matter from nearby companion stars and that many
|
From page 5... ...
1973: Observations by the Skylab satellite confirm earlier indications that high-velocity solar-wind streams flow from "coronal holes," solar regions of much reduced x-ray and ultraviolet emission; these streams are later recognized as the source of many geomagnetic disturbances on the Earth. 1974: Radio observations of the pulsar PSR 1913 + 16 show that it orbits a companion star every 6 hours; precise measurements of this binary pulsar later confirm the prediction of the General Theory of Relativity that a binary-star system radiates energy in the form of gravitational waves.
|
From page 6... ...
satellite is launched; observations establish temperature scales for hot stars, reveal resemblances between quasars and Seyfert galaxies, and show that mass loss from stars at rates high enough to affect stellar evolution is nearly universal. 1979: Isotopic analysis of cosmic rays shows conclusively that they constitute a sample of matter with a nucleosynthetic history different from that of the Sun.
|
From page 7... ...
The development of highly efficient detectors for optical astronomy permitted the study of extremely faint and previously inaccessible objects with large telescopes and enabled smaller facilities to become major research tools. New technologies for telescope construction employing thin mirrors or mirror segments, ultrashort focal lengths, lightweight support structures, and innovative designs for domes or housings-made it both technically and economically feasible to build much larger telescopes for optical and infrared studies.
|
From page 8... ...
Another example of impressive progress recorded during the 1970's is our increased understanding of the structure and energy balance of the interstellar medium. Ultraviolet spectroscopy provided by the Copernicus and JUE satellite observatories, coupled with x-ray observations from rockets and satellites, has revealed that large regions of interstellar space are filled with gas heated to hundreds of thousands of degrees by shock waves from supernova explosions; other ultraviolet studies have shown that mass loss is a feature of normal stellar evolution.
|
From page 9... ...
Stars are born in clouds of gas and dust that form at low temperatures and radiate predominantly in the infrared and millimeter wavelength regions of the spectrum. Despite the great improvements in detectors and ground-based instrumentation in these wavelength regions during the 1970's, a new generation of observational facilities both in space and on the ground will be required to furnish the increases in spatial and spectral resolution needed for detailed comparison of regions of star formation with increasingly sophisticated theoretical models.
|
From page 10... ...
The technological developments of the 1970's permit these problems to be attacked now, with a high degree of effectiveness, and at reasonable cost. The maturing of space astronomy, advances in detectors, reduction in cost of computers, and new technologies for constructing telescopes have already been mentioned; to these developments must be added more specialized advances, such as the refinement of radio Vim; short-wavelength antenna design and fabrication; new approaches to the detection of cosmic rays, neutrinos, and gravitational waves; and infrared interferometry.
|
From page 11... ...
A different and still more wonderful view of the cosmos will almost surely be revealed to us in the years ahead. The discoveries of our generation have brought us to the threshold of a revolution in physical thought, in which the properties of elementary particles may hold the key to understanding the early history of the Universe and in which the quantum properties of gravitation, unrecognized in the theories of Newton and Einstein, may play a central role in understanding cosmic evolution.
|
From page 12... ...
A 2-,um infrared image of the center of the Galaxy, hidden by 30 magnitudes of optical extinction. (Photo courtesy of G
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.