Radio Observations of Interstellar Hydroxyl Radicals

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Science  25 Aug 1967:
Vol. 157, Issue 3791, pp. 881-889
DOI: 10.1126/science.157.3791.881


The discovery of the radio frequency lines of OH gave the first positive evidence of the existence of OH in the interstellar medium. In the 3½ years that have intervened, many observations have revealed totally unexpected anomalies in the radio-spectral properties of interstellar OH. As a result, no reliable astrophysical information has been derived from the OH observations, but a large body of information is waiting to be unraveled. The interpretations of the data which have been made, such as the values derived for OH/H abundance ratios or for the kinetic temperatures of interstellar gas clouds, must be viewed with caution. They may turn out to be drastically in error, once the origin of the OH emission and absorption is fully understood.