Tip of the Red Giant Branch

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The Tip of the Red Giant Branch (dt Translation:. Tip of the Red giant branch ) is a method of astronomy to determine the distance of star clusters and galaxies . It is based on the fact that all red giants have an identical brightness when the helium flame ignites in the infrared.

In the evolution of stars of medium mass, the ashes of hydrogen burning collects in a helium core in the center of the stars. While the hydrogen burning moves outwards in a bowl , the star in the Hertzsprung-Russell diagram moves upwards along the giant red branch. In the degenerate core, the helium fuses explosively , the luminosity being dependent on the mass of the core and only slightly dependent on the metallicity . Since the ignition of the helium nucleus depends mainly on the density, the helium flash occurs in all stars between 4 and 12 billion years old with the same nuclear mass.

The luminosity of the red giants at this point in time only differs by 0.05 mag in the mid-infrared, and this spectral range is only slightly influenced by the extinction . The method is available for all star systems with stars of the old population II , which are present in all types of globular clusters and galaxies. In order to be able to determine the tip of the giant branch with a high degree of accuracy, about 100 stars within 1 mag are required at the top of the red giant branch.

literature

  • Myung Gyoon Lee, In Sung Jang: The Tip of the Red Giant Branch Distances to Type Ia Supernova Host Galaxies. II. M66 and M96 in the Leo I Group . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1306.2306v1 .
  • GA Tammann, B. Reindl: The supernova Ia 2011fe in M101, its tip of the red-giant branch (TRGB) distance, and the value of H_0 . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1112.0439v1 .
  • M. Bellazzini: The Tip of the Red Giant Branch . In: Astrophysics. Solar and Stellar Astrophysics . 2007, arxiv : 0711.2016v1 .