Carl Wilhelm Wirtz was an astronomer who spent his time between Germany and the Observatory of Strasbourg.

He observed a systematic redshift of nebulae, which was difficult to interpret in terms of a cosmology in which the Universe is filled more or less uniformly with stars and nebulae.

He used the equivalent in German of K-correction. The term continues to be used in present-day observational cosmology, but Wirtz's observational evidence that the Universe is expanding is not often mentioned.

It is unclear whether or not he was aware of the cosmological implications of his empirical result.

External links

• Search for Carl Wilhelm Wirtz's work [NASA Astrophysics Data System (ADS)]

• Wirtz, Carl Wilhelm, 1918, Astronomische Nachrichten, volume 206, p.109 - article with first known use of the term K-correction - missing from the ADS (adsabs.harvard.edu) database but present in any good astronomical library