I Dark Matter Size to be seen in our solar system

Albertgauss

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Hello,

My question is, how much dark matter (any of mass, volume, density, etc) would we have to have in our solar system for us to detect it? My guess is that we would detect the dark matter through gravitational lensing or the perturbation of planetary orbits.

On previous posts about dark matter, it was quoted that

"To expand on Bandersnatch's reply. the amount of DM in a sun-sized volume weighs only about a ton."

and also

"that at the distance from the galactic centre at which the Sun orbits, there is roughly a small asteroid-worth of DM contained within a 1 cubic AU volume of space"

I understand there is very little dark matter in a single solar system.
 
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Direct searches for dark matter (in underground detectors) could find it within a year or two.
Astrophysical searches within our solar system cannot find the amount of dark matter detected within - the uncertainties in other masses are way too large. We would a few orders of magnitude more dark matter to have a chance. These exclusion limits are a factor ~100,000 too weak.
 

Albertgauss

Gold Member
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A year or two? Wow, that's much sooner than expected that I thought. That's very interesting, and I will be on the look for that. If they can't find dark matter in these latest experiments, what will they then conclude? Are these searches geared for very specific types of dark matter?

In regards to dark matter within our solar system, I would expect it to be in our arms of the milky way or in the center, as that seems to be where it is supposed to be located. Did I read that correctly what we cannot the dark matter within our solar system? It seems like that would be the easiest dark matter to detect, since such dark matter would be closest to us. Maybe not. How is it explained that we would not be able to see dark matter in other galaxies way far away but not our own? Has anyone ever done the following tests?

Has anyone ever done any gravitational lensing of objects directly on the opposite side of the galaxy from us; as the light from the other side of the galaxy passes near the supermassive black hole at our Milky Way center on its way to us, does such light bend when it falls on our telescopes on our planet?

Does this relate to maybe that we see dark matter in other galaxies from billions of years ago, but that perhaps in our more local galactic neighborhood--and thus more recently in time that we can see--this dark matter spreads-out-more/is-distributed to not be detected. That is, does dark matter behave differently in galaxies further away in time than nearer the present.

Do stars in our own galaxy have the discrepancies in their orbital speeds around our galaxy that we find in stars of other galaxies that have dark matter?
 
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Dark matter detectors double their sensitivity every year (numbers). I don't think it is likely, but in principle a signal can appear quickly.

XENON1T has the best exclusion limit based on just a month of data-taking. If we are extremely lucky and dark matter is "just around the corner", within a year they could have a very promising signal, and a clear discovery within two years.
If they can't find dark matter in these latest experiments, what will they then conclude? Are these searches geared for very specific types of dark matter?
There are many models of dark matter, and different experiments look for different things. Weakly interacting massive particles (WIMPs) is the model that gets the most attention. See the linked article for a brief discussion. There are many other models around, and other experiments looking for those (ALPS, CAST, DAMPE, and many more).

Dark matter should form a roughly spherical halo in the Milky Way.
Did I read that correctly what we cannot the dark matter within our solar system?
Not via its gravitational influence, that is way too small on such a scale (the solar system is tiny - not much dark matter within its volume). You need something as large as a part of the galaxy to notice the additional mass. If we would see its gravitational influence in the solar system something would be wrong with the dark matter models.
All the direct detection experiments look for dark matter interacting with the detector, of course.

Microlensing with various foreground sources has been seen many times, but dark matter doesn't contribute notably to the lensing individual stars or black holes produce for the same reason.
We know the amount of dark matter in our galaxy from other measurements (most notably the galactic rotation curve).
 

Albertgauss

Gold Member
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Excellent. Thank you for taking the time to answer. I think this question is answered completely for me for the moment.
 

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