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Optical and Radio Information

Published online by Cambridge University Press:  30 March 2016

Hugh M. Johnson
Hugh M. Johnson*
Affiliation:
Lockheed Missiles and Space Company

Extract

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The six or eight optically identified X-ray sources comprise starlike objects and extended supernova remnants in the Galaxy, well as as a radio galaxy and a quasar. Both X-ray and radiofrequency radiation penetrate the entire galactic plane, but only two or three galactic radio sources have been identified with X-ray sources. This has led Hayakawa et al. to postulate that detectable X-ray sources are not farther than 1 kpc. However, other studies suggest that there is a cluster of a few intrinsically bright sources actually near the galactic nucleus and a scattering of weaker sources near the sun.

The distances of X-ray sources can be estimated from extinction by interstellar gas or intergalactic gas on spectra above 10 Å, but the method ultimately depends on the radio and optical data of the gas. Conversely, interstellar densities of certain elements with large photo-ionization cross-sections may be determined from the absorption of X-rays, after calibration of source distances by the methods of optical astronomy.

Type
Joint Discussions
Information
Highlights of Astronomy , Volume 1: Highlights of Astronomy. As presented at the XIIIth General Assembly of the IAU, 1967 , 1968 , pp. 206 - 209
Copyright
Copyright © Reidel 1968

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