Calculating the Feeding Rate of Supermassive Black Holes to Power Quasars

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Homework Help Overview

The discussion revolves around calculating the feeding rate of supermassive black holes to power quasars, focusing on the relationship between mass, luminosity, and the rate of accretion. The subject area includes astrophysics and gravitational physics.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the equation relating luminosity to mass and the rate of change of mass with respect to radius. There are attempts to clarify the definitions of deltaM and deltaR, as well as how to apply the Schwarzschild radius in calculations.

Discussion Status

The discussion is ongoing, with participants seeking clarification on the algebraic steps involved in the calculations. Some guidance has been offered regarding the use of the Schwarzschild radius and the need to understand the units of the derived values.

Contextual Notes

Participants are navigating the complexities of the problem, including assumptions about constants and the definitions of variables in the context of the equations provided. There is an emphasis on understanding the physical implications of the calculations.

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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