Can we determine the rotation speed of a black hole?

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SUMMARY

The discussion centers on the determination of a black hole's rotation speed, specifically referencing Kerr black holes, which possess a theoretical rotation due to angular momentum conservation. Direct measurement of this rotation is impossible due to the event horizon's properties. The conversation highlights a theory suggesting that emitted light from a black hole's surroundings, particularly in x-ray binaries, can provide insights into the black hole's spin, with ultrasoft x-ray components potentially indicating the spin's strength. However, skepticism remains regarding the effectiveness of current methods to derive intrinsic spin accurately.

PREREQUISITES
  • Understanding of Kerr black holes and their properties
  • Familiarity with angular momentum conservation principles
  • Knowledge of x-ray binary systems and their significance in astrophysics
  • Basic grasp of event horizons and their observational limitations
NEXT STEPS
  • Research the methods for calculating black hole spin using x-ray emissions
  • Study the implications of angular momentum in astrophysical contexts
  • Explore the characteristics of ultrasoft x-ray components in black hole studies
  • Investigate the limitations of current theories regarding black hole spin measurement
USEFUL FOR

Astronomers, astrophysicists, and students interested in black hole research and the complexities of measuring cosmic phenomena.

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Is it possible to calculate the rotation speed of a black hole? Idid not find anything on this on google.

thanks
 
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A Kerr black hole has a theoretical rotation component due to conservation of angular momentum. It cannot be measured directly as we cannot observe anything occurring inside the event horizon. I doubt it's meaningful to talk about rotataion with respect to the event horizon. For discussion, see
http://science.howstuffworks.com/black-hole.htm/printable
 
I heard in class of a theorie that would use the light emmited from the black hole surroundings to calculate the rotation speed, anyone familiar with these theories?
thanks
 
I heard about that. In an x-ray binary in which a black hole is believed to be the compact object, it has been suggested that the strength of an ultrasoft x-ray component is directly related to the black hole's spin.
Check out section 8.2 of the following:
http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.astro.44.051905.092532
 
Good link, maria, but, I am unconvinced the authors have derived an effective way to derive the intrinsic spin of a black hole.
 
thank you for this link.
 

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