Editor's Summary

23 October 2008

Galactic structure: a simple answer

At first glance a galaxy looks pretty complicated: each contains billions of stars subject to many influences including gravity, rotation and radiation. The hierarchical theory of galaxy formation — currently fashionable — holds that they are assembled from smaller pieces, through many mergers of cold dark matter, and that the properties of an individual galaxy are determined by six independent parameters. Now a survey of 200 individual galaxies suggests that things are simpler than that, and that galactic structure is controlled by one single parameter. Though frustratingly, it is not yet clear which parameter that is. This level of organization is at odds with hierarchical galaxy formation and the predictions of cold dark matter cosmology.

News and ViewsAstrophysics: How do galaxies form?

A study of galaxies indicates that galaxy formation may be regulated by a single parameter. This unexpected finding shows that prevailing views on the process could need revision.

Sidney van den Bergh


LetterGalaxies appear simpler than expected

M. J. Disney, J. D. Romano, D. A. Garcia–Appadoo, A. A. West, J. J. Dalcanton & L. Cortese