OT: Runaway black hole!

Perrin · #1 November 20th, 2002, 06:18 PM

MSNBC Article

Ragnarok · #2 November 20th, 2002, 06:25 PM

Very interesting read.

Ed Kolis · #3 November 20th, 2002, 10:11 PM

Oh, good, I was afraid your galaxy map had started rearranging itself on its own!

Never knew there were any black holes this near by, though... should make for some good scientific study!

Kamog · #4 November 22nd, 2002, 08:17 AM

That is a very interesting article. I wonder how they were able to figure out the path the black hole takes through the galaxy? Even though it is moving at high speed, it must take billions of years to complete one cycle through the galaxy. Given that we have observed the object for only a tiny fraction of time relative to its orbit, it must be extremely difficult to deduce its complete path.

Hmm, well, I suppose that if they are able to determine the object's speed and direction, we should be able to calculate its path. They probably modeled the galaxy to be a radially symmetrical disk with a bulge in the center and thinning out at its edges. Similarly, there will be a mass density gradient that is high at the center and decreasing toward the edge. At any particular point in the black hole's trajectory, the influence of gravity from the galaxy can be modeled as a single point in the center containing all the mass within the circle drawn from the center to the radius of the black hole's current location. As the black hole moves along, the radius will change, so the force of gravity will continuously have to be re-calculated at small increments. Of course, we will have to assume that the black hole never comes close enough to any stars or other objects to significantly alter its smooth path through the galaxy.

Will · #5 November 22nd, 2002, 10:37 AM

Remember, there's a lot of stuff moving around out there. In order to predict the orbit of the black hole, you can look at the movement of other stellar bodies in the black hole's immediate path. That will allow you to refine the path, so you can look ahead a little further, allowing you to refine a little more, so you can look a little further... and so on. They don't have to (wrongly) assume that the galaxy is homogeneous. There are spots with lots of clusters, and spots that are fairly empty.

oleg · #6 November 22nd, 2002, 07:14 PM

Quote:

Originally posted by Kamog:
That is a very interesting article. I wonder how they were able to figure out the path the black hole takes through the galaxy? Even though it is moving at high speed, it must take billions of years to complete one cycle through the galaxy. Given that we have observed the object for only a tiny fraction of time relative to its orbit, it must be extremely difficult to deduce its complete path.

Hmm, well, I suppose that if they are able to determine the object's speed and direction, we should be able to calculate its path. They probably modeled the galaxy to be a radially symmetrical disk with a bulge in the center and thinning out at its edges. Similarly, there will be a mass density gradient that is high at the center and decreasing toward the edge. At any particular point in the black hole's trajectory, the influence of gravity from the galaxy can be modeled as a single point in the center containing all the mass within the circle drawn from the center to the radius of the black hole's current location. As the black hole moves along, the radius will change, so the force of gravity will continuously have to be re-calculated at small increments. Of course, we will have to assume that the black hole never comes close enough to any stars or other objects to significantly alter its smooth path through the galaxy.

You can estimate speed from Dopler shift and distance from paralax.