# Question about black hole sizes

• fillipeano
In summary, determining the size of a black hole can be done theoretically based on its mass, but there are currently no actual measurements. The size of a black hole is typically expressed as the size of its event horizon, which is relatively easy to calculate. However, there are different theories about the interior of black holes, which means the event horizon may not be the actual boundary. Ultimately, the singularity at the center of a black hole has no size.
fillipeano
Is there any way to determine how big a black hole is? I googled the question but I didn't find any answer.

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.

Last edited:

## What is a black hole?

A black hole is a region in space where the gravitational pull is so strong that not even light can escape from it. It is formed when a massive star dies and collapses under its own gravity.

## How big can a black hole be?

The size of a black hole is determined by its mass. As more matter is pulled into the black hole, its size and gravitational pull increases. Some black holes can be as small as a single atom, while others can be millions or even billions of times the size of our sun.

## What is the largest known black hole?

The largest known black hole is known as TON 618 and is estimated to have a mass of 66 billion times that of our sun. It is located in a distant galaxy and is about 10.4 billion light years away from Earth.

## Can black holes merge together?

Yes, black holes can merge together in a process known as a "black hole merger". This occurs when two black holes orbit each other and eventually merge into one larger black hole. This phenomenon has been observed by scientists through the detection of gravitational waves.

## What happens when an object enters a black hole?

Once an object crosses the event horizon (the point of no return) of a black hole, it will be pulled towards the center of the black hole. As it gets closer, it will experience extreme tidal forces and will eventually be torn apart and added to the mass of the black hole.

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