Calculating the Feeding Rate of Supermassive Black Holes to Power Quasars

AI Thread Summary
Quasars are powered by supermassive black holes consuming gas and stars, with typical masses around 10^7 solar masses and luminosities of about 10^39 W. The discussion focuses on calculating the feeding rate required to sustain this luminosity using the equation L = GM/R * deltaM/deltaR. Participants express confusion about the variables deltaM and deltaR and how to apply them in calculations. There is a request for clarification on the algebra involved in substituting the Schwarzschild radius into the luminosity equation. The conversation emphasizes the need for understanding the units of deltaM/deltaR to solve the problem accurately.
amt2124
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Homework Statement


Quasars arise when supermassive black holes swallow nearby gas, or even
entire stars. Their masses are typically 10&7 solar masses, and their luminosities are
typically around 10&39 W. Hide the children! Roughly how many stars must one of
these monsters eat per year, in order to power that luminosity?

Homework Equations



L = GM/R * deltaM/deltaR

The Attempt at a Solution


So far I can find deltaM/deltaR like the professor said we should. I am having trouble understanding where we go from there.
 
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amt2124 said:
So far I can find deltaM/deltaR like the professor said we should. I am having trouble understanding where we go from there.
Perhaps you can expound a bit upon what deltaM and deltaR are, and how you have found them?
 
gneill said:
Perhaps you can expound a bit upon what deltaM and deltaR are, and how you have found them?
I assumed that I am able to plug in the schwarzschild radius for the radius, G is a constant, and I am given the luminosity and mass. When I plug those in I can solve for deltaM and deltaR (which is the rate of accretion).
 
Can you show the algebra that you did, plugging the Schwarzschild radius into your luminosity equation?
 
gneill said:
Can you show the algebra that you did, plugging the Schwarzschild radius into your luminosity equation?
 

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Okay. Now what are the units on your ΔM/ΔR value?
 
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