On the Ratio of the Total to Selective Absorption
The ratio of total to selective absorbtion, R, has been found to remain constant as dust is processed in clouds from low to high density, through H II regions and open clusters, and returned to the interstellar medium. R has the same value in dense dust clouds as it has in H II regions of different ages. Variations in R values obtained from stars in H II regions may be due to errors in special type classification. Globular cluster diameters show no tendency to increase with distance from the Sun when R=3.2 is used. Large grains evidently do not exist in the interstellar medium. There is no evidence for neutral extinction in the Galaxy at large.
KeywordsInterstellar Medium Open Cluster Spectral Type Globular Cluster Dust Cloud
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