Testing the no-hair theorem with observations of black holes in the electromagnetic spectrum

Tim Johannsen, Dimitrios Psaltis

Research output: Contribution to journalArticle

18 Scopus citations


According to the no-hair theorem, astrophysical black holes are uniquely described by their mass and spin. In this paper, we review a new framework for testing the no-hair hypothesis with observations in the electromagnetic spectrum. The approach is formulated in terms of a Kerr-like spacetime containing a quadrupole moment that is independent of both mass and spin. If the no-hair theorem is correct, then any deviation from the Kerr metric quadrupole has to be zero. We show how upcoming VLBI imaging observations of Sgr A as well as spectroscopic observations of iron lines from accreting black holes with IXO may lead to the first astrophysical test of the no-hair theorem.

Original languageEnglish (US)
Pages (from-to)528-532
Number of pages5
JournalAdvances in Space Research
Issue number3
Publication statusPublished - Feb 1 2011



  • Accretion, accretion disks
  • Black hole physics
  • Galaxy: center
  • Gravitation
  • Gravitational lensing: strong
  • Line: profiles

ASJC Scopus subject areas

  • Aerospace Engineering
  • Space and Planetary Science

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