You know how the planets orbit the sun more slowly, the farther away they are? Well the stars in the galaxy do the same thing. The problem of predicting their speeds is more difficult than with the planets because the mass of the galaxy is much more dispersed. Consequently, the gravitational effects are variable because of the differing amounts of matter as you move away from the center.
What they do is measure the speed of stars believed to be at certain distances from the center. Then they graph a line representing those speeds, from the center out to the edge. This would be the gravitational curve of a galaxy. Of course it will start high and come down, but it is usually not a perfect curve. It serves as a kind of gravitational fingerprint for the particular galaxy.
Edit: Okay, thumber, I think the rotational curve for our galaxy shows pretty much what we would expect if it had NEITHER a supermassive black hole NOR dark matter. Maybe a central black hole a hundred or a thousand solar masses. Not billions.
b6473d82e47c479ca94a81a5daeff14If our photograph voltaic device which incorporates our planet Earth is an element of the Milky way, how is it achieveable for us to look up interior the nighttime sky and see the Milky way interior the very a strategies distance? QUOTE because of the fact a million) the Milky way is somewhat large (greater than our photograph voltaic device); 2) the Milky way surrounds the photograph voltaic device; 3) we are able to degree the distances of stars interior the Milky way, and it confirms that we are interior the disk; 4) many stars exist interior the Milky way; 5) different galaxies that are stated have their disks constituted by skill of stars; 6) there is no reason to think that the solar would be so specific that it could be separated from something of the Universe. we are rather plenty interior the Milky way.
The simple answer is that the rotation curve of our galaxy strongly implies that there's more mass present than can be accounted for, i.e., "dark matter."
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You know how the planets orbit the sun more slowly, the farther away they are? Well the stars in the galaxy do the same thing. The problem of predicting their speeds is more difficult than with the planets because the mass of the galaxy is much more dispersed. Consequently, the gravitational effects are variable because of the differing amounts of matter as you move away from the center.
What they do is measure the speed of stars believed to be at certain distances from the center. Then they graph a line representing those speeds, from the center out to the edge. This would be the gravitational curve of a galaxy. Of course it will start high and come down, but it is usually not a perfect curve. It serves as a kind of gravitational fingerprint for the particular galaxy.
Edit: Okay, thumber, I think the rotational curve for our galaxy shows pretty much what we would expect if it had NEITHER a supermassive black hole NOR dark matter. Maybe a central black hole a hundred or a thousand solar masses. Not billions.
b6473d82e47c479ca94a81a5daeff14If our photograph voltaic device which incorporates our planet Earth is an element of the Milky way, how is it achieveable for us to look up interior the nighttime sky and see the Milky way interior the very a strategies distance? QUOTE because of the fact a million) the Milky way is somewhat large (greater than our photograph voltaic device); 2) the Milky way surrounds the photograph voltaic device; 3) we are able to degree the distances of stars interior the Milky way, and it confirms that we are interior the disk; 4) many stars exist interior the Milky way; 5) different galaxies that are stated have their disks constituted by skill of stars; 6) there is no reason to think that the solar would be so specific that it could be separated from something of the Universe. we are rather plenty interior the Milky way.
The simple answer is that the rotation curve of our galaxy strongly implies that there's more mass present than can be accounted for, i.e., "dark matter."