Kennicutt–Schmidt law

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In astronomy, the Kennicutt–Schmidt law (or simply Schmidt law) is an empirical relation between the gas density and star formation rate (SFR) in a given region. The relation was first examined by Maarten Schmidt in a 1959 paper where he proposed that the SFR surface density scales as some positive power of the local gas surface density.[1] i.e.


In general, the SFR surface density is in units of solar masses per year per square parsec and the gas surface density in grams per square parsec . Using an analysis of gaseous helium and young stars in the solar neighborhood, the local density of white dwarfs and their luminosity function, and the local helium density, Schmidt suggested a value of (and very likely between 1 and 3). All of the data used were gathered from the Milky Way, and specifically the solar-neighborhood.

In 1989, Robert Kennicutt found that the H intensities of every galaxy in a sample of 7 could be fit with the Schmidt law.[2] More recently, he examined the connection between gas density and SFR for nearly 100 nearby galaxies to estimate a value of .[3]


  1. ^ Schmidt, Maarten (1959). "The Rate of Star Formation". The Astrophysical Journal. 129: 243. Bibcode:1959ApJ...129..243S. doi:10.1086/146614.
  2. ^ Binney, James; Merrifield, Michael (1998). Galactic Astronomy (1st ed.). Princeton, NJ: Princeton University Press. p. 524. ISBN 978-0-691-02565-0.
  3. ^ Kennicutt, Robert C., Jr. (1998). "The Global Schmidt Law in Star-forming Galaxies". The Astrophysical Journal. 498 (2): 541–552. arXiv:astro-ph/9712213. Bibcode:1998ApJ...498..541K. doi:10.1086/305588.CS1 maint: Multiple names: authors list (link)