His dissertation (1920) was titled: The relations of the globular clusters and spiral nebulae to the stellar system.

Lundmark's work contributed to the later famous Great Debate over whether nebulae were galaxies or concentrations of glowing gas.

He also often appeared in the Swedish national radio with programs on popular astronomy and the history of science.

[1] The Wolf-Lundmark-Melotte Galaxy is named after Lundmark, Max Wolf and Philibert Jacques Melotte.

A recently found publication from 1930 shows Knut Lundmark to be the first to realise that the universe must contain much more mass than we can observe, now known as dark matter.