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

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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

• INTRODUCTION
• DISTANCES AND GENERAL CHARACTERISTICS OF EXTRAGALACTIC NEBULAE
• Distance Determination with the help of the Period-Brightness Relationship for Cepheids
• Statistics of the brightest stars of a nebula
• Distance determination of nebulae using their total apparent magnitude
• THE REDSHIFT OF EXTRAGALACTIC NEBULA. RELATIONSHIP BETWEEN DISTANCE AND REDSHIFT
• SPECULATIONS CONCERNING THE REDSHIFT
• Cosmological theories
• Direct influence of existing matter in space on the frequency of light
• COMMENTS ON THE VELOCITY DISPERSION IN THE COMA CLUSTER OF NEBULAE
• COSMIC RAYS AND REDSHIFTS

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