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- Thread starter exmarine
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Vanadium 50

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Note that while MOND does well on galactic scales, it does not do well at larger scales.

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Are we – our solar system – on the flat part of our own galaxy’s rotation curve? Are we rotating “too fast” about the galaxy center?

Is our solar system then permeated with Dark Matter? If so, wouldn’t that require reformulation of Newton dynamics / Kepler’s laws?

What distribution of DM is suspected in our galaxy, and within our solar system?

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Bandersnatch

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Here are example graphs with plotted approximated mass distribution and its contribution to rotation curves in the MW (precision is exaggerated):Are we – our solar system – on the flat part of our own galaxy’s rotation curve? Are we rotating “too fast” about the galaxy center?

The sun is at approx. 8 kpc from the centre. As you can see, it's a roughly flat curve at that distance.

The graph on the right shows that there's approx. 25% more dark matter than baryonic (i.e. Disc+Bulge) matter enclosed within the radius of the orbit of the Sun. However, unlike baryonic matter DM does not clump, so its density in any given region of space is extremely low - so low that any effect it might have on the dynamics within the solar system is negligible.Is our solar system then permeated with Dark Matter? If so, wouldn’t that require reformulation of Newton dynamics / Kepler’s laws?

The graph to the right allows you to make a rough calculation of the density of DM in the solar system using simple algebra - the result being about 10

These values are too low to have a noticeable effect, unless you look extremely carefully - the first of the two papers quoted above actually attempts just that. As such, they could not affect formulation of Kepler's, Newton's and other laws or experiments with insufficient precision.

The distribution in its simplest form is shown on the graph above (right). Linear growth of enclosed mass translates to a spherically symmetric cloud whose density is falling with the square of the distance.What distribution of DM is suspected in our galaxy, and within our solar system?

Unless it turns out DM can sufficiently interact with matter (e.g. weak force), it will be freely streaming through the solar system with density corresponding to the density in the galactic DM profile at this distance from its centre.

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Thanks for the info and the papers! Fascinating subject.

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