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The Center of Galaxys

  1. Oct 27, 2005 #1
    When I see a picture of deep outer space and it shows a lot of galaxys flying around there is always a big "Sun" like, center of gravity that pulls all the many solar systems around it what is that? a red giant or some type of supernova?
  2. jcsd
  3. Oct 27, 2005 #2
    I believe what you are talking about is the Black Hole that is theorized to be at the center of each galaxy. It is supposed to be a supermassive type.
  4. Oct 27, 2005 #3


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    Actually, I think s/he's talking about the galactic bulge, not the black hole at its centre. The bulge is merely a collection of stars so numerous and densely packed that it looks like one giant ball of light.

    http://sspp.gsfc.nasa.gov/hh/freestar/images/galaxy.jpg" [Broken]
    http://www.eso.org/outreach/press-rel/pr-2000/phot-07a-00-normal.jpg" [Broken]


    http://www.science.ankara.edu.tr/astronomy/astro/turkce_ast/ders/genel_ders/ders_gif/lec19_04.gif" [Broken]
    http://atropos.as.arizona.edu/aiz/teaching/a204/images/gal_schematic.gif" [Broken]
    http://tycho.bgsu.edu/~laird/phys655/class/milky_way_schematic.gif" [Broken]

    http://en.wikipedia.org/wiki/Galactic_bulge" [Broken]

    If that's *not* what you mean, can you elaborate - perhaps with some examples?
    Last edited by a moderator: May 2, 2017
  5. Oct 29, 2005 #4
    exactly, What causes these nuclear bulges to pull stars and dust to their center,and when these bulges cause galaxys to merge is there a chance of two universes colliding with one another.
  6. Oct 29, 2005 #5


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    It's not simply the bulges that cause galaxies to collide, it's the sum total of the gravity of all the individual stars.

    When galaxies collide, there isn't really a lot of stellar collision - the stars mostly pass each other. But their paths are drastically affected, destroying the structure of the galaxy. Google "colliding galaxies". It really doesn't have anything to do with "universes".
  7. Oct 30, 2005 #6
    The Gravity of what(what starts it)
  8. Oct 30, 2005 #7
    The stars clump together there because of the galaxy's supermassive black hole at its center. As said, "It's not simply the bulges that cause galaxies to collide, it's the sum total of the gravity of all the individual stars." Also, when galaxy's collide, it has nothing to do with two universes. During the collision it is actually more of a peaceful dance, although I'm not saying there arn't any collisions, but a lot less then you would think. Then the two supermassive black holes at the center of each galaxy would collide and merge together.
  9. Oct 30, 2005 #8


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    Hmm, that's putting the cart before the horse. The stars initially clump together due to their mutual gravitational attraction, then the material closest to the center compacts enough to form a supermassive black hole.
  10. Oct 31, 2005 #9


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    Hi Janus! Well, I think in the case of galaxy formation we are not yet in the position of knowing which is the cart and which is the horse.

    The problem of large scale structure, galactic halo and galaxy formation is a problematic one at the moment. The standard idea is the hierarchial model, yet observations of very large galaxies at high red shift HUDF-JD2, a 6 x 1011Msolar galaxy at z = 6.5, when the universe was 860 Myrs old, (age given by Ned Wright's calculator allowing for DE), and massive quasars with high iron abundancy, would indicate that perhaps they might have formed the other way round!

    Last edited: Oct 31, 2005
  11. Nov 3, 2005 #10
    Somebody please can give some references to the "Black holes in the center of galaxies" issue?, some standard reference articles?
  12. Nov 6, 2005 #11
    I doubt that gravity causes galaxies to collide, they have to already be pretty much moving towards each other.
  13. Nov 7, 2005 #12


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  14. Nov 9, 2005 #13


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    Gravity is pretty much the only thing that can induce a true galaxy collision. Otherwise, the galaxies would just pass through one another -- they're mostly empty space!
  15. Nov 9, 2005 #14


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    Last edited by a moderator: Apr 21, 2017
  16. Nov 9, 2005 #15


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  17. Nov 18, 2005 #16
    I just thought that I would add my 2 cents worth on this topic. I'm not a physicist and I don't know much about galaxy collisions or what a typical galaxy collision consist of but I would have to agree that even when galaxies are drawn together that the occurances of collissions among individual stars would likely be very small.

    I'm a 3d animator and technical artist. A few months ago out of curiosity I decided to create a true scale model in Maya (3d modeling and animation application) of our solar system and several surrounding stars. When you navigate a true scale 3d model of our solar system ore even a very small section of our galaxy you begin to realize how truly empty space really is. The volume of intergalactic bodies such as stars and planets are so small compared to the distances that seperate them that the chances of stars actually colliding would most likely never occur if it weren't for gravity and the large number of bodies involved. If Maya was a more commonly available application I would upload my models for those who are curious to check out. I even created an animation of a vessel traveling from Earth to Mars just for fun. I think I gave it a speed of 0.1 c. At that rate I think it still took my ship about 4 1/2 minutes to reach Mars. I locked a camera to the rear view of the ship, which I thought would be a dramatic effect, but believe me, it was pretty boring to watch the trip.


    Actually, now that I think about it I had to increase the speed to c in order to compress the animation from 43 1/2 minutes to 4 1/2 minutes so I could actually watch it. Initially I created the animation at 0.1 c but decided I didn't want to watch a ship flying through space for over 43 minutes.
    Last edited: Nov 18, 2005
  18. Nov 20, 2005 #17
    Hello Raziel

    When you see a picture of a distant galaxy, it is important to rememeber that the image you see covers a vast region of space. Also remember that the picture you see like the one in the link below for the Sombrero galaxy, contain many millions or even many billions of individual stars.


    So when you see pictures like this it is virtually impossible for individual stars to be resolved, that is seen. Therefore they appear as one very bright region.

    (galaxies are given catalogue numbers, so that they can be identified easily, M104 (NGC 4594), and assigned a morphological type, this describes some of the visual features of the galaxy, the Sombrero galaxy is hubble type Sa,and is found in Virgo),

    At the centre of the Sombrero galaxy you can see what looks like a very big bright star. This is in fact a collection of a vast number of stars and is called the 'bulge'. The bulge is only found in galaxies that have spiral arms, the outer regions of the bulge are dominated by the light from old stars, usually called 'Population II stars'. The exact mechanisms for the formation of bulges in galaxies is still a matter of debate. Without doubt though is that these bulges need gravity to form, but they may also need the merger of other smaller galaxies to help form them.

    This brings us to your next point.

    Galaxy merger is believed to have been happening since galaxies first formed in fact they are still on-going processes. There are some wonderfull images available of this happening,

    http://www.space.com/scienceastronomy/astronomy/hubble_stephans_010719.html [Broken]

    It's also important to remember that these events do not just happen in remote regions of our universe, they happen to our Galaxy too,


    The picture above shows that our own Galaxy, the Milky Way, is currently undergoing a "collision" with another galaxy. This other galaxy is called the Sagittarius Dwarf galaxy. I use the term 'collision' losely as it is very unlikely that any stars/matter will collide. (If you do some research from the sites above you will see why they don't really collide).

    I hope some of this helps you understand what is going on out there!
    Last edited by a moderator: May 2, 2017
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