[Lewis Thomson (OP)]

Listener David submitted this cosmic conundrum to The Naked Scientists in a hope to find the answer.

"How are black holes formed and why are they often at the centre of galaxies?"

Do you know the answer? Discuss your research in the comments below...

[evan_au]

It is known that galaxies do collide, and the supermassive black holes at their centers merge to form even larger black holes.
- The chaos of a galaxy merger transfers angular momentum between the two groups of stars, resulting in a rush of stars settling in closer & closer to the central black hole(s), causing it to grow faster, by accretion

In today's universe, "small" black holes (1.5-10x the mass of our Sun) form from the collapse of stars at the end of their life.
- It is thought that the early universe was almost all hydrogen and helium, so these hypothetical "Population III" stars would have behaved a bit differently than today's  "metal-rich" stars, forming many giant stars perhaps 100 times the mass of our Sun, and forming black holes that were larger - perhaps 30x the mass of our Sun
- It is known that these "stellar mass black holes" can collide to form larger black holes - the LIGO/VIRGO gravitational wave detectors have detected a number of events which formed black holes 60x the mass of the Sun.

However, the universe is not old enough for the stellar-mass black holes to grow into supermassive black holes (millions to billions of times the mass of our Sun) by individual collisions
- So it is a mystery how the supermassive black holes grew so fast in the early universe, forming the quasars that are visible at high redshift
- It is hoped that the new James Webb Space Telescope, with its ability to view distant/very old galaxies may shed some (infra-red) light on the subject.

See: https://en.wikipedia.org/wiki/Supermassive_black_hole#Formation

[vdblnkr34]

One day I watched a video about how black holes and planets are formed. And the voice in the video mentioned that all planets and black holes begin with a spin. Something happens and everything starts to rotate in one place (like pool water going to the drain) until certain temperatures met and then planet is formed. For black hole to appear needs a lot of heat thousands of degrees. Dont remember. For a planet to form needs less, like 18,000 C. What happens during this, no idea. What spins around in that place, no idea. Why it start to spin, no idea.

[Lewis Thomson (OP)]

This question has now been answered and you can listen to it through this link.
https://www.thenakedscientists.com/podcasts/question-week/why-are-black-holes-centre-galaxies

[Zer0]

Very Nicely explained indeed.
Thank You Dr Becky Smethurst!
👍
imho - BHs are neither Black nor Holes.

[lindsaykarny]

They are believed to be at the center of every galaxy because they have such gravitational power and strength that they can pull the rest of the dust, asteroids, planets, and suns close to them.

I work as a spam removed

[JLindgaard]

 If 2 black holes interacted or collided, they'd destroy their galaxies. What happens when none existent space is below absolute 0? Space is empty so there is no time dilatation or distortion allowed. There is simply no inverse function to matter existing. Why math is so much fun. It simply does not allow for a physical inverse function.
 We all know 4^-1 is 1/4, right? Yet there is no functional relationship in that expression. Kind of why math doesn't allow for dark matter.

[Kryptid]

 If 2 black holes interacted or collided, they'd destroy their galaxies.

That seems unlikely. No only are the energies not large enough, but the energy released is primarily in the form of gravitational waves (which mostly pass through matter unabsorbed).

[Colin2B]

If 2 black holes interacted or collided, they'd destroy their galaxies. What happens when none existent space is below absolute 0? Space is empty so there is no time dilatation or distortion allowed. There is simply no inverse function to matter existing. Why math is so much fun. It simply does not allow for a physical inverse function.
 We all know 4^-1 is 1/4, right? Yet there is no functional relationship in that expression. Kind of why math doesn't allow for dark matter.

This gibberish is why you were confined to only posting in new theories, you were warned that you would be banned if you ignored that restriction.

[evan_au]

If 2 black holes interacted or collided, they'd destroy their galaxies.

Galaxy collisions are fairly common, across the universe - in fact, the Milky Way and Andromeda galaxies are expected to collide in about 5 billion years (but the collision will occur over several billion years).

The collision of two galaxies causes many stars to be flung into the void; these stars are hard to see as they have low surface brightness. Other stars will be swallowed by the two central black holes.

It is thought that two orbiting black holes will tend to clear out a space around them, out to about twice their orbital radius - by adding those stars to their accretion disks, or by flinging them out of the way (or both).
https://en.wikipedia.org/wiki/Interacting_galaxy#Galaxy_collision

But there are galaxies which appear to have experienced a black hole merger, and the surrounding galaxy is still intact. These galaxies show a jet whose direction suddenly changes.
https://en.wikipedia.org/wiki/X-shaped_radio_galaxy