Janus Posted April 14, 2019 Share Posted April 14, 2019 22 hours ago, MaximT said: Is a sum of mass orbiting a Black Hole, could contribute to the gravity force maintaining the rotation in orbit around the center of the galaxy, to make that galaxy objects spin around the center? Is that sum of mass (all orbiting objects) could reduced the theoretical mass of the Black Hole itself, creating a empty, cannot be seen, zone around it, at the place of dilating it's volume to achieved the same density? Can objects orbit a common center of gravity? Yes. Can this explain or effectively reduce the predicted mass of the central black hole? No. It's not just the orbital speeds involved, but the shapes of the orbits. When you look at the plot of the orbits of those stars you will note that since they are very elliptical, sometimes a given star will be closer to the center than other stars and sometimes further away. Any star that is further from the center than you are will not contribute to the force you feel pulling you towards the center.* By plotting the shape of the orbit as well as its speed at different points, you can calculate just how much of the total mass of the entire system has to be actually be located at the center. This is what gives you the mass of the BH. * An extreme example of this would be a spherical cloud of stars with a hollow at it center. For any star in that cloud its orbit is determined by the stars as close or close to the center than it is, the other stars have no effect. An object that wandered into the central hollow, would be behave as if there were no stars surrounding the hollow at all. 1 Link to comment Share on other sites More sharing options...
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