How Can We Determine the Size of a Black Hole?

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SUMMARY

The size of a black hole is theoretically determined by its mass, with 1 solar mass equating to approximately 5.9 kilometers in diameter. Current measurements of black hole diameters are not available, but future observations may provide data on the black hole at the center of the Milky Way. The size of a black hole is typically expressed as the size of its event horizon, which can be calculated, while the singularity itself is understood to have zero volume. The event horizon serves as the boundary of the black hole, based on prevailing theories of black hole interiors.

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Is there any way to determine how big a black hole is? I googled the question but I didn't find any answer.
 
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If you mean its diameter, you can determine it theoretically from its mass:
1 solar mass = 5.9 km,
1000 solar masses = 5900 km and so on.
AFAIK, there are no actual measurements of a diameter. Maybe within the next 10 years, they will have measurements of the BH in the center of the Milky Way.
 
Black hole size is usually expressed as the size of its event horizon, which is pretty easy to calculate.
 
yes, but it should be noted that the EH is an effect caused by the BH. the actual BH itself has no size, ie, the singularity proper has zero volume.
 
jnorman said:
yes, but it should be noted that the EH is an effect caused by the BH. the actual BH itself has no size, ie, the singularity proper has zero volume.

That's only if a certain picture of black hole interiors is correct. Several different theories are available with quite different outcomes. Thus the event horizon is the boundary as far as we know or close to.
 
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