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Sun can absorb almost 200,000 more Suns? 
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#1
May1014, 11:51 AM

P: 42

The maximum massenergy allowable inside a sphere to ensure a static Star is obtained from Buchdahl’s Theorem:
M(max)=4/9*R/G*c^2 Calculations show that Sun can absorb almost 200,000 more Suns and remain it its current radius and stay away from collapsing. Is this correct? 


#2
May1014, 12:21 PM

Mentor
P: 11,837

With 200 000 times its mass, the sun would be a black hole where the event horizon would be roughly at the current surface of sun. For realistic objects, this is certainly beyond a collapse.
If you try to produce such an object by adding more and more mass from the outside, however, you produce a star with extremely strong stellar winds that will prevent more mass from getting added. 


#3
May1014, 01:09 PM

P: 42

How much massenergy could fit into the current radius of Sun, referring to the condition of a static Star obtained from Buchdahl’s Theorem, which sets the upper limit. 


#4
May1014, 05:40 PM

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Sci Advisor
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Sun can absorb almost 200,000 more Suns?



#5
May1014, 06:35 PM

Mentor
P: 16,321

Pretty much the only conditions of the theorem that the sun satisfies are that it has a mass and a radius.



#6
May1114, 12:17 AM

P: 42

Let me quote from Sean Carroll in his book Spacetime and Geometry.
After introducing the maximum massenergy allowable equation on page 234 he writes: "Thus, if we try to squeeze a greater mass than this inside a radius R, general relativity admits no static solutions; a star that shrinks to such a size must inevitably keep shrinking, eventually forming a black hole. We derived this result from the rather strong assumption that the density is constant, but it continues to hold when that assumption considerably weakened." 


#7
May1114, 03:15 AM

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The point that the theoretical upper limit given by the theorem wouldn't be reached if you used the hydrogen/helium/other mix that the sun uses is the point I was trying to convey. 


#8
May1114, 03:22 AM

P: 42




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