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Messier 81 , a galaxy with spiral arms on the outside and bulge in the central area.

As Bulge ( Engl. Bulge , "bulge", "bulge") is called in astronomy the dense central region of a spiral galaxy . The bulge stands out clearly from the rest of the galaxy . On the one hand, it appears much brighter due to its high density , on the other hand, it usually bulges far beyond the plane of the pane . For galaxies very distant, the bulge is often the only thing that can be seen of the galaxy. A bulge is similar to an elliptical galaxy .

According to recent research, there is often a black hole inside the bulge , including in the center of our Milky Way . The ratio between the mass of the bulge and that of the black hole (in other words “the mass fraction of the bulge that is in the black hole”) is 0.2% (according to Ho, 1999 and Wandel, 1999) and 0.6% % (according to Kormendy and Richstone, 1995) constant for different galaxies. The sizes of the percentages are controversial in research.

See also

Individual evidence

  1. Luis C. Ho: Supermassive Black Holes in Galactic Nuclei. In: S. K. Chakrabarti (Ed.): Observational Evidence for the Black Holes in the Universe. 1999, p. 157.
  2. ^ A. Change: The Black Hole-to-Bulge Mass Relation in Active Galactic Nuclei. In: The Astrophysical Journal. 519, pp. L39-L42, 1999, doi : 10.1086 / 312106 .
  3. John Kormendy, Douglas Rich Stone: Inward Bound - The Search for Supermassive Black Holes in Galactic Nuclei. In: Annual Review of Astronomy and Astrophysics. 33, 195, pp. 581-624, doi : 10.1146 / annurev.aa.33.090195.003053 . bibcode : 1995ARA & A..33..581K .
  4. ^ Max Camenzind: Compact objects in Astrophysics. White Dwarfs, Neutron Stars and Black Holes. Springer, Berlin 2007, ISBN 978-3-540-25770-7 , p. 465.
  5. ^ Andreas Eckart, Rainer Schödel, Christian Michael Straubmeier: The black hole at the center of the Milky Way. Imperial College Press, London 2005, ISBN 1-86094-567-8 , p. 218.