Blackhole Movement

[Deepwater6]

Do blackholes move independently or are they just moving along with their Galaxy? If so are they propelled by the gravitational forces of the stars near them? If there are no stars near a blackhole are they stationary? Since there are millions of blackholes in our Galaxy can we axpect one to wander into our solar system some day other than the Andromeda collision? thx

[CraigD]

Do blackholes move independently or are they just moving along with their Galaxy? If so are they propelled by the gravitational forces of the stars near them? If there are no stars near a blackhole are they stationary?

Gravitationally, black holes affect and are affected by neighboring massive bodies no differently than stars of the same mass, so black holes have the same galactic orbits as the stars of which they’re remnants.

 

It’s not uncommon for black holes to be found as one of the stars in a binary star system – Cygnus X-1, generally considered the first confirmed observed black hole, is such as system. Though at about 6000 ly, we can’t image Cygnus X-1 in much detail, we’re pretty sure that up close, it’s would be a spectacular sight to the naked eye.

 

Since there are millions of blackholes in our Galaxy can we axpect one to wander into our solar system some day other than the Andromeda collision? thx

We should no more expect a close encounter with a black hole than with a visible star.

 

It’s helpful to understand that black holes come in 3 basic sizes: star-mass ones, with masses of about 3 to 20 (or perhaps as much as 40) times our Sun’s; supermassive ones, with masses of 100,000s to 1,000,000,000s (billions) of solar masses, which it appears are found in the core of every galaxy; and intermediate-mass ones, masses 30 to 1,000,000 SMs , which are essentially supermassive BHs that formed in smaller star formations like globular clusters, where there just aren’t enough stars to make a supermassive BH. Stellar BHs formed from the collapse of individual stars (which must be at least about 20 SMs, or no BH). Bigger BHs must form from the combining of Stellar BHs or BHs and ordinary stars.

[Cyberia]

Deepwater6. As the galaxy spins, so the stars in it move (apparently there is some "up and down" movement as well as around the centre). So black holes just being "dead stars" move too. Stars do not move uniformly and over very long time periods there are encounters with other stars and black holes but nothing in any future that matters to mankind.

 

The collision with Andromeda is some billions of years away so nothing we will ever know about. But stars are generally so far apart that there will not be that many collisions, but by the same token, it does give a good chance for new planet formation from close encounters and even from the debris of encounters. Of course, with a black hole involved, all you are going to end up with is a larger black hole. It might have some trouble swallowing a much larger star but it'll get there eventually.

[maddog]

Deepwater,

 

The other point is that it is now currently thought that all Black Holes spin. Conditions could arrive that if otherwise we wouldn't like.

 

maddog