Institute of Astronomy

Accretion disc temperatures

Published on 07/01/2014 
Question: 

Hi, I've been looking everywhere online trying to find out what the roughly average temperature you would expect to find in the acceleration disk of a black hole. Nearly every scientific document published that I can find doesn't go into anymore detail than "hot enough to produce x-rays". Thanks for your time.

As you may know the colour something hot appears changes depending on how hot it is, starting from a very dull red, to a brighter red then orange, yellow and white as it gets hotter.  This is because as an object gets hotter the wavelength at which it emits light most strongly moves to shorter wavelengths and higher energies.  For very high temperatures scientists tend to think in terms of what this peak wavelength is rather than the temperature itself, this is why everything that you have found just says 'hot enough to produce X-rays'.  To be hot enough for the peak of emission to be in the X-ray range the material would have a temperature of around 300,000-300,000,000K.

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Page last updated: 7 January 2014 at 12:33