How Long Could Gravitational Contraction Power the Sun?

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Homework Help Overview

The discussion revolves around the gravitational potential energy of the Sun and how it relates to the timescale over which gravitational contraction could power the Sun's luminosity. The original poster seeks hints regarding the calculation of this timescale using the formula involving gravitational potential energy and luminosity.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the definition and value of the Sun's luminosity (L_sun) and its role in the calculation. There is an emphasis on plugging in values into the equation provided by the original poster.

Discussion Status

The discussion is ongoing, with participants seeking clarification on the hints provided and the specific values needed for the calculations. Some guidance has been offered regarding the use of L_sun in the equation, but there is no explicit consensus on the next steps.

Contextual Notes

Participants are navigating the need for specific values and definitions, particularly regarding L_sun, to proceed with the calculations. There is an indication of confusion about the hints given, suggesting a need for clearer communication of ideas.

Tuugii
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Homework Statement


The gravitational potential energy W of a self-gravitating sphere of mass M and radius R depends on the detailed distribution of mass within the sphere, but it is generally of order of magnitude -GM^2/R. For the Sun, W_sun = -2G(M_sun)^2/R. What is the timescale
t = -(1/2)(W_sun)/(L_sun) over which gravitational contraction could have supplied the power radiated by the sun at it's present rate?

please give some hints, thanks a lot.
 
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what is L_sun ?

(iknow that it is Luminosity, but try to find the value)
 
malawi_glenn said:
what is L_sun ?

(iknow that it is Luminosity, but try to find the value)


thanks for the reply. But I didn't understand what was your hint... :)
 
Tuugii said:
thanks for the reply. But I didn't understand what was your hint... :)

I meant, have you tried just to plug in the value of L_sun into that eq?
 

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