# B Calculating Weight and mass of entire black hole

1. May 7, 2018

### hyunxu

Its pretty tough to calculate the entire mass and weight of entire black hole.But how we will give a approximate value? How we will calculate its mass and weight?

Could you list some stuffs that caught into the black hole?

Has any scientist ever visited a black hole and collected data on it?

Do each black hole have their own name?

Last edited by a moderator: May 7, 2018
2. May 7, 2018

### davenn

how about you do some reading and YOU list some things that might get drawn into a black hole

what do you think would be the answer to that and why ?

some have names

Dave

3. May 7, 2018

### Drakkith

Staff Emeritus
The easiest way is to measure the orbital period of objects that are in orbit of the black hole, a relatively straightforward calculation depending on what method you are using to measure the object with. Alternatively you could use General Relativity if you observe a gravitational lensing effect, but that is much, much harder to calculate.

No. The nearest black hole is hundreds of light years from Earth if my memory serves. No one has even been outside of the solar system yet. Heck, we haven't even been to another planet yet.

4. May 7, 2018

### hyunxu

The easiest way is to measure the orbital period of objects that are in orbit of the black hole, ---> do black holes have orbits?

5. May 7, 2018

### Drakkith

Staff Emeritus
Certainly. We could replace the Sun with a 1-solar mass black hole and the planets would continue on their merry way in their present orbits.

6. May 7, 2018

### Staff: Mentor

Pretty much everything in space is orbiting something or has something orbiting it. Watching stars orbit something invisible is one of the only ways to know a black hole is there!

7. May 9, 2018

8. May 9, 2018

### hyunxu

9. May 28, 2018

### rbelli1

No so merry for us!

Weight doesn't really have meaning in this context.

BoB

10. May 30, 2018

### JMz

Quite true, but (Keplerian) mass certainly does and is the usual meaning of "weight" when discussing astronomical objects.

11. May 30, 2018

### rbelli1

The OP specifically called out both mass and weight:

BoB

12. May 30, 2018

Good point!