Astronomy and Astrophysics Space Science in the Twenty-First Century -- Imperatives for the Decades 1995 to 2015 (1988) / Chapter Skim
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2. Science Objectives
2. Science Objectives
Pages 8-18
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From page 8... ...
Temperatures, pressures, magnetic field strengths, and radiation densities range similarly across extremes. A practical consequence of this great variety of conditions is a huge range of cosmic sizes, of velocities, and of time scales on which dynamic processes take place.
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From page 9... ...
Higher angular resolution, as well, is needed to focus on extremely compact sources. Such compact sources will also need to be studied both at high spectral resolution and across the widest possible dynamic range to reveal internal motions and chemical composition.
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From page 10... ...
The Early Universe, Unidentified Matter, and the Origin of Galaxies "Big bang" cosmology the theory espousing the explosive origin of the universe met a crucial experimental test with the 1965 discovery of the cosmic blackbody background radiation. That measurement yielded a ratio of photons to protons in the universe and permitted calculation of the abundances of light elements produced in the first few minutes after the big bang.
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From page 11... ...
SIRTF will search for cold matter, such as brown dwarfssubstelIar bodies emitting energy by virtue of a slow contraction that liberates gravitational potential energy. This search for cold matter by SIRTF will set limits on the baryonic composition of the dark matter component in our galaxy.
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From page 12... ...
. _ The Physics of Collapse and Strong Fields The discovery of radio pulsars, neutron stars, and candidate black holes in x-ray binary stellar systems demonstrated that some stars collapse beyond the density of atomic nuclei.
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From page 13... ...
Astronomers have identified several objects believed to be stellar black holes in orbit around a normal stellar companion. With the aid of computer simulations, theorists are now studying the accretion process near rotating black holes.
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From page 14... ...
Such observations will be of extraordinary interest in testing the black hole mode} of active galactic nuclei and in studying the novel relativistic effects expected in the vicinity of black holes. Both the Long-Baseline Optical Space Interferometer (LBOSI)
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From page 15... ...
We also know through observations of secondary photons in the radio, and sometimes in the gamma-ray region, that powerful particle acceleration must occur in almost all classes of extragalactic objects. In fact, the nonthermal radio spectra of most bright spiral galaxies seem to have almost identical slope, indicating that some common, but as yet poorly understood, mechanism governs the acceleration and propagation of the parent electrons in these galaxies.
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From page 16... ...
Our instruments have so far been unable to detect any of the manifestations of such bodies: reflected light, infrared reradiation of stellar light, wobble on the plane of the sky, or periodic radial velocity variation. It should be possible in the 1990s to undertake a meaningful search for extrasolar planets by using special high-resolution spectrographs to look for the radial velocity variations in a parent star produced by planetary gravitational pulls.
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From page 17... ...
Instruments specifically designed for this purpose, with spatial resolution of the order of 10-3 to 10-4 arcsec, could obtain images of other solar systems. Furthermore, they could carry out spectrophotometric analyses of the chemical composition of the planetary atmospheres.
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From page 18... ...
Studies of the magnetic activity of stars, and even direct imaging of stellar surfaces, enable us to extrapolate physical theories of solar activity and magnetic dynamos to objects like our Earth. Eventually, these studies may contribute to a deeper understanding of climatic variations on Earth, of the terrestrial dynamo action (including periodic reversals of the Earth's magnetic field)
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