# What does a black hole orbit?

• B
• Timothy Schablin
In summary, the conversation discussed an interesting interactive experiment about black holes and their orbiting behavior. It was mentioned that black holes orbit around the center of mass of the BH + Star system, also known as the barycentre. It was also clarified that black holes are not magical star-gobbling machines, but rather compact masses subject to gravity. They can have a similar mass to a large star and behave in the same way. However, due to their compact size, one can get much closer to a black hole than a regular star, causing a significantly stronger gravitational force.

#### Timothy Schablin

Found this interesting interactive experiment.
http://hubblesite.org/explore_astronomy/black_holes/encyc_mod3_q14.html

In the interactive, it looks like the black hole is orbiting around something. What would it orbit around? Or am I looking at it wrong?

The center of mass of the BH + Star system.

davenn
berkeman said:
The center of mass of the BH + Star system.
yup, or more commonly known as the barycentre

https://en.wikipedia.org/wiki/BarycenterDave

davenn said:
yup, or more commonly known as the barycentre
Show-off!

berkeman said:
Show-off!
hahaha

berkeman
It's orbiting around a plan ol' star.

Black holes are not magical star-gobbling machines. They are compact masses, subject to gravity, just like any other mass. More to the point, they act on other things like a regular mass does.

If the Sun were replaced by a black hole of the same mass, Earth and the other planets - even Mercury would all happily continue on their merry way as if nothing had changed.

Black holes can easily have a mass similar to a large star, and so will behave like a star in every way. The only tricky bit to dealing with them is that you can get a lot closer to them than you can to a regular star.

For example, you cannot get closer to the sun than its surface - which is 400,000 miles from its centre. But a BH of one solar mass would be less than 13 miles in radius. So you could get 399,983 miles closer to that same one solar mass. And gravitational force squares as you halve the distance - making it about 10 million times greater - when you're that close.

That's where you start to run into problems.

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Delta2

## 1. What is a black hole?

A black hole is a region in space with a gravitational pull so strong that nothing, including light, can escape it. It is formed when a massive star dies and its core collapses.

## 2. What does a black hole orbit around?

A black hole does not orbit around anything. Instead, objects orbit around the black hole due to its strong gravitational pull.

## 3. How does a black hole affect nearby objects?

A black hole's strong gravitational pull can distort the space and time around it, causing nearby objects to orbit around it or even be pulled into it.

## 4. Can a black hole have multiple objects orbiting around it?

Yes, a black hole can have multiple objects orbiting around it, similar to how planets orbit around a star.

## 5. Can we see a black hole orbiting another object?

No, we cannot directly see a black hole orbiting another object as light cannot escape it. However, we can observe the effects of its gravitational pull on surrounding objects.