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Feb7-09, 05:28 PM
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Quote Quote by v2kkim View Post
Regarding the bright bar in our Galaxy Dave is right. we are looking at our galaxy from side not top view. But some photons can orbit BH though unstable. Remember that the space time is so greatly bent near BH that the light can make a circular orbit, which also can be considered as an extreme case of gravitational lensing, but these photons does not have strong density and maybe theoretical calculation so far.
By the way, I do not understand what causes our galaxy contract ? due to gas and material collision etc ?
Yes, energy loss due to heating of gasses and collisions. Also, because of the simply massive amount of stars orbiting, the perturbations introduced by random close encounters tends to destabilize the orbits over time.

Quote Quote by dj1972
So lets create a mess. Clouds of gas and debris and what nots starts to billow in the middle of nowhere. (Isnt this a nebula? And isnt a nebula an exploding star?) Well, in the center of this mess starts a so called galaxy we'll call dj020709 (LOL I made it so I can name it whatever) Stars are forming towards the center from these clouds of gas and debri and what nots from collapses of gas and gravity and friction packing itself into a ball of huge gas. (I know its more technical then this but hey) Well they start to orbit each other or whatever and over a few billion years one explodes. A massive one. Lets say over 10 SM. And wah lah a large BH is formed, starts to eat up stuff and at the same time more stars are being formed just packing the center because its the best place to get stars because of all the gases and debri and such, they want to be where the action is.
There are a few things that would work to make this model not as simple as you've stated. Yes, stars would form towards the center of this dense cloud of gas and dust, but solar wind usually clears out the surrounding disk of material relatively soon. So, for all intents and purposes, the stellar systems (be they lone, binary, etc.) are essentially alone in their local neighborhoods, even in areas of relatively "high" density. The most that happens when one turns into a black hole is it begins to accrete matter from its companion star. It will not gobble up everything in the nucleus, for as we have said, it behaves (gravitationally, and non-locally) exactly the same as a star on the grand scale of things. And stars almost never collide or interact on more than light year scales.