Published in Helvetica Physica Acta, Vol. 6, p. 110-127, 1933.

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(Die Rotverschiebung von extragalaktischen Nebeln)

Fritz Zwicky

(Translated by H. Andernach heavily editing a raw translation from

Abstract: This gives a description of the most essential characteristics of extragalactic nebulae, as well as of the methods used to investigate these. In particular, the so-called redshift of extragalactic nebulae is discussed in detail. Various theories which have been proposed to explain this important phenomenon, are briefly discussed. Finally, it will be indicated to what extent the redshift promises to become of importance for the study of cosmic rays.

Table of Contents

Special terms were interpreted as follows:

- Nebel = nebula (not galaxy, to preserve the original flavor of the text)

- Fluchtgeschwindigkeit = recession velocity (not escape velocity, as there is no escape here...)

- Perioden-Helligkeits-Beziehung = Period-Brightness Relationship (not period-luminosity, to preserve the original word "Helligkeit")

- penetrating radiation = cosmic rays