Super Massive Black Holes - Some Myths
What are they?
What evidence is there that they exist?
Lets start with a disclaimer, I’m not an astrophysicist, and have only ever done one course fully on astrophysics… and this is quite ‘new’ so there may be problems with this post, if anyone notices any PLEASE TELL ME!!!
These are black holes, that are at the centre of most galaxies (as far as we can tell).
That doesn’t sound very bad or confusing does it? You can imagine that everything eventually slows and falls to the centre of the galaxy and is sucked into a black hole until it would become quite large.
A supermassive black hole has a mass between 
and solar masses! That’s 100,000 suns, at the small end!
There’s 4 main ideas for how they form, the first is basically the one mentioned above. The second is the creation of a single star of a few thousand solar masses from a large dust cloud which then collapses, this star would then undergo another callapse straight into a black hole without having to go supernova. The third model is for a dense group of stars called a stellar cluser, which would callapse. And finally the fourth idea is quite simply that they’re left over by the big bang due to some unknown effect.
Now why isn’t one of these hypothesis prefered to the others, well mainly because there just isn’t enough evidence, we know they exist (see below), but that’s about it. The first two have a couple of holes which even as a non-expert I can see quite clearly, the first idea, if this was true we’d expect to see a range of black hole sizes from stellar sized up to 
, but we don’t they’re either small (a few solar masses) or supermassive. The problem with the other approaches is all pretty similar you need to have enough mass in a small enough area without it haivng so much angular momentum that it wont callapse. With the cloud callapse method there would be the problem that you’ve got to over come fragmentaion which happens to reduce the Jeans mass to create normal every day stars….
OK then, so these things seem pretty wacky, there’s not many of them about, how the **** do we know they exist?
Well we’ve measured the dopplar shift of matter very close to the centre of close by galaxies, and wow the stuff is spinning fast! So fast infact that the only way it could be possible is if there was a supermassive black hole at the centre.
There’s also be quite alot of work to try and find the one at the centre of our very own galaxy, and it’s supposed to have a mass of about 3.7million suns! That’s alot of mass! There’s a research group at UCLA which has published a significant amount of data in this area, lots of information can be found on their website:
http://www.astro.ucla.edu/~ghezgroup/gc/
And of course there’s always wikipedia!
http://en.wikipedia.org/wiki/Supermassive_black_hole
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