Mystery of the hidden cosmos.

[Nicolaas Vroom]

In Scientific American of July 2015 there is an article with the title:
"Mystery of the hidden cosmos."
The article starts with sentences like:
"The speed of its rotation cannot be explained by applying the laws of
physics to the disk's visible matter." and "If the visible matter was all
there was. Andromeda etc should not exist." and "Cosmologists believe that
some unseen kind of matter - dark matter - surrounds and permeates
Andromeda etc adding the necessary gravitational force to keep them
spinning as observed".
In the article they also speak about dark charge (one positive one
negative), dark photons and dark electromagnetism.
The problem is IMO there exists strictly speaking no visible matter.
The only matter to explain galaxy rotating curves are its objects i.e.
baryonic matter. Small baryonic objects are invisible. As such all earth
sized objects are invisible. They only become visible when they grow
in size, become hot both inside and outside and become visible like
our sun, because now they emit photons we humans can observe.
(which by itself is already amazing)
At the same time they also should not grow to much in size because
than they become invisible again (as black holes, which do not emit,
photons which strictly speaking may not be correct)
I'm aware that BH can be detected indirectly.
My point is that in order to explain the rotation curves you should take
care for all baryonic mass specific outside the observable disc.
The issue is partly how much baryonic matter is there in the regions
between stars. For our sun this region starts with the spherical Oort
Cloud, but in real each star has an Oort Cloud.
When this amount of matter is large it should be included in the
calculations of a galaxy rotation disc.

Anyway when our Galaxy contains lots of darkmatter why does our
own solair system not contain anything. If it does it could explain
the forward movement of the planet Mercury (which it should not?)

Nicolaas Vroom
http://users.pandora.be/nicvroom/

[[Mod. note --
1. Earth-sized and even smaller baryonic objects may be detectable by
microlensing. See, for example, arXiv:1001.3349.
2. When we use a measured galaxy rotation curve to estimate (model)
the mass distribution, we're implicitly including ALL mass that
gravitates, including the Oort clouds of all the stars.
3. When we say our galaxy contains "lots" of dark matter, that means
"enough to be dynamically significant on the scale of the galaxy".
If you do the numbers, you'll see that a dark-matter density can
be big enough to be dynamically significant on the scale of the
galaxy (i.e., significantly affect the galactic rotation curve),
yet the amount of dark matter within our solar system is still
far too tiny to be detected in planetary motions. The key point
is that the galaxy is HUGE relative to our solar system, so even
a tiny density (too small to be important within our solar system)
can add up to a significant amount of matter on a galactic scale.
-- jt]]

[Nicolaas Vroom]

Op zaterdag 11 juli 2015 20:54:24 UTC+2 schreef Nicolaas Vroom:

>
> [[Mod. note --
> 1. Earth-sized and even smaller baryonic objects may be detectable by
> microlensing. See, for example, arXiv:1001.3349.

I agree. The question is what is the total mass of the objects in our
Galaxy related to size.
See the article "The Grand Illusion" in Astronomy of November 1992 by
Ken Croswell. What the article implies is that the majority of stars in Our
Galaxy are Red and White dwarfs. That means a lot of mass comes from red
stars. My interpretation is 50%. K dwarfs 25% and all others 25%.
And that inturn means IMO that the amount of matter from even
smaller objects can be huge (which is all baryonic)

> 2. When we use a measured galaxy rotation curve to estimate (model)
> the mass distribution, we're implicitly including ALL mass that
> gravitates, including the Oort clouds of all the stars.

There are always three questions:
1. How much matter do we need to simulate a galaxy rotation curve.
2. How much baryonic matter can we observe including blackholes.
3. How much matter is missing.
4. What is the density (distribution) of this matter.
5. Could all this missing matter be baryonic ?

> 3. When we say our galaxy contains "lots" of dark matter, that means
> "enough to be dynamically significant on the scale of the galaxy".

At the same time this is also true for baryonic matter.
I have also done some simulations.
For some information go here:
http://users.telenet.be/nicvroom/dark_mat.htm

> If you do the numbers, you'll see that a dark-matter density can
> be big enough to be dynamically significant on the scale of the
> galaxy (i.e., significantly affect the galactic rotation curve),
> yet the amount of dark matter within our solar system is still
> far too tiny to be detected in planetary motions.

I fully agree with you that a certain amount of matter is missing
dynamically significant etc.
The issue is that we must be sure that it is not baryonic before
we can start to investigate something else.

> The key point
> is that the galaxy is HUGE relative to our solar system, so even
> a tiny density (too small to be important within our solar system)
> can add up to a significant amount of matter on a galactic scale.

The question is what is this missing (dark) matter density compared to
the Oort Cloud density.

The fact that there is (almost) no dark matter in our solar system
implies me to postulate that there is no dark matter around the direct
neighbourhood of any star (planetary system)

> -- jt]]

Nicolaas Vroom.

[Phillip Helbig (undress to reply)]

In article <1b14d8b8-29d6-40cb...@googlegroups.com>,

Nicolaas Vroom <nicolaa...@pandora.be> writes:

> > [[Mod. note --
> > 1. Earth-sized and even smaller baryonic objects may be detectable by
> > microlensing. See, for example, arXiv:1001.3349.
> I agree. The question is what is the total mass of the objects in our
> Galaxy related to size.
> See the article "The Grand Illusion" in Astronomy of November 1992 by
> Ken Croswell.

That is 23 years old! That is a LONG TIME in modern astronomy.

> What the article implies is that the majority of stars in Our
> Galaxy are Red and White dwarfs.

Yes.

> That means a lot of mass comes from red
> stars.

Yes.

> My interpretation is 50%.

I'm sure that there are better estimates.

> K dwarfs 25% and all others 25%.
> And that inturn means IMO that the amount of matter from even
> smaller objects can be huge (which is all baryonic)

Both red and white dwarfs shine. We have an idea how many there are.
They are not unaccounted for.

> > 2. When we use a measured galaxy rotation curve to estimate (model)
> > the mass distribution, we're implicitly including ALL mass that
> > gravitates, including the Oort clouds of all the stars.

Right. And since the resulting mass is always larger than everything we
know about, we invoke dark matter. Or MOND.

> There are always three questions:
> 1. How much matter do we need to simulate a galaxy rotation curve.
> 2. How much baryonic matter can we observe including blackholes.
> 3. How much matter is missing.
> 4. What is the density (distribution) of this matter.
> 5. Could all this missing matter be baryonic ?

Any review of dark matter can answer these questions. Maybe one could
just about manage to have all missing matter in spiral galaxies be
baryonic, pushing the limits, but there is evidence for more dark
matter, which makes it more probable that it exists in spiral galaxies
as well.

[Gary Harnagel]

On Tuesday, July 14, 2015 at 2:40:47 AM UTC-6, Phillip Helbig (undress to reply) wrote:
>
> In article <1b14d8b8-29d6-40cb...@googlegroups.com>,
> Nicolaas Vroom <nicolaa...@pandora.be> writes:
> >
> > > [[Mod. note --
> > > 1. Earth-sized and even smaller baryonic objects may be detectable by
> > > microlensing. See, for example, arXiv:1001.3349.
> >
> > I agree. The question is what is the total mass of the objects in our
> > Galaxy related to size.
> > See the article "The Grand Illusion" in Astronomy of November 1992 by
> > Ken Croswell.
>
> That is 23 years old! That is a LONG TIME in modern astronomy.
>
> > What the article implies is that the majority of stars in Our
> > Galaxy are Red and White dwarfs.
>
> Yes.
>
> > That means a lot of mass comes from red
> > stars.
>
> Yes.
>
> > My interpretation is 50%.
>
> I'm sure that there are better estimates.

I did a semi-quantitative estimate from the number of type O
through type M with their mass ranges and came up with about 41%
of the total O through M mass.

> > K dwarfs 25%

I'm close at 24%, so I agree.

> and all others 25%.

I'm talking about percentages of SHINING stars, so I get 35% for all
others, making a total of 100%.

> > And that inturn means IMO that the amount of matter from even
> > smaller objects can be huge (which is all baryonic)

Well, by extrapolating frequency and masses below type M stars, I get
about another 45% for brown dwarves and maybe another 10% for smaller
objects. The masses of even smaller objects drops to insignificance
(even though the extrapolation says they are much, much more numerous
than stars and brown dwarves.

If this extrapolation has any validity, it means that "agglomerated"
baryonic matter is far short of being able to explain the dark matter
problem. Additional gas has been detected in galactic haloes and has
been identified as supernova ejections. One would expect that ejection
should be symmetric so much of it was ejected into the galactic disk,
but this can only amount to a few percent.

> Both red and white dwarfs shine. We have an idea how many there are.
> They are not unaccounted for.
>
> > > 2. When we use a measured galaxy rotation curve to estimate (model)
> > > the mass distribution, we're implicitly including ALL mass that
> > > gravitates, including the Oort clouds of all the stars.
>
> Right. And since the resulting mass is always larger than everything we
> know about, we invoke dark matter. Or MOND.
>
> > There are always three questions:
> > 1. How much matter do we need to simulate a galaxy rotation curve.
> > 2. How much baryonic matter can we observe including blackholes.
> > 3. How much matter is missing.
> > 4. What is the density (distribution) of this matter.
> > 5. Could all this missing matter be baryonic ?
>
> Any review of dark matter can answer these questions. Maybe one could
> just about manage to have all missing matter in spiral galaxies be
> baryonic, pushing the limits, but there is evidence for more dark
> matter, which makes it more probable that it exists in spiral galaxies
> as well.

Yes, there is a real deficit problem unless the microlensing technique
can demonstrate that planet-sized objects are thicker than fleas on a dog
(i.e., my extrapolation wildly underestimates the number of these bodies
by several orders of magnitude).

Gary

[Nicolaas Vroom]

Op dinsdag 14 juli 2015 10:40:47 UTC+2 schreef Phillip Helbig:

> That is 23 years old! That is a LONG TIME in modern astronomy.

I have no more recent information

> I'm sure that there are better estimates.

You can also also claim that there are 60% Red and white dwarfs, 20% K dwarfs
all others 20% (equally divided in G stars, A+F stars and larger stars).

> > K dwarfs 25% and all others 25%.
> > And that inturn means IMO that the amount of matter from even
> > smaller objects can be huge (which is all baryonic)
>
> Both red and white dwarfs shine. We have an idea how many there are.
> They are not unaccounted for.

Correct. This defines "all" visible baryonic matter
That means, as a matter of argument, that there could exist almost the
same amount of brown stars, planet sized stars and dust
(all "invisible" baryonic matter).

> > > 2. When we use a measured galaxy rotation curve to estimate (model)
> > > the mass distribution, we're implicitly including ALL mass that
> > > gravitates, including the Oort clouds of all the stars.
>
> Right. And since the resulting mass is always larger than everything we
> know about, we invoke dark matter. Or MOND.

IMO when the calculated theoretical mass is more than the observed baryonic
mass the first candidate to invoke is baryonic grain sized mass.
To modify from Newtonic mechanics to MOND is IMO not necessary.

> > There are always three questions:
> > 1. How much matter do we need to simulate a galaxy rotation curve.
> > 2. How much baryonic matter can we observe including blackholes.
> > 3. How much matter is missing.
> > 4. What is the density (distribution) of this matter.
> > 5. Could all this missing matter be baryonic ?
>
> Any review of dark matter can answer these questions. Maybe one could
> just about manage to have all missing matter in spiral galaxies be
> baryonic, pushing the limits, but there is evidence for more dark
> matter, which makes it more probable that it exists in spiral galaxies
> as well.

In our solor system there is "no" dark matter. The line of evidence
is linked to the trajectories of known planets at each epoch.
These trajectories could not be explained by the existance of the
known planets. The missing matter was explained by the observations
of a new baryonic planet, not by invoking darkmatter
which in essence is a new kind of physics.
See: https://en.wikipedia.org/wiki/Discovery_of_Neptune.
Only in the case of Mercury a new kind of physics was required.

Nicolaas Vroom

[Jos Bergervoet]

On 7/16/2015 3:38 AM, Gary Harnagel wrote:
> On Tuesday, July 14, 2015 at 2:40:47 AM UTC-6, Phillip Helbig (undress to reply) wrote:

...

>> Any review of dark matter can answer these questions. Maybe one could
>> just about manage to have all missing matter in spiral galaxies be
>> baryonic, pushing the limits, but there is evidence for more dark
>> matter, which makes it more probable that it exists in spiral galaxies
>> as well.
>
> Yes, there is a real deficit problem unless the microlensing technique
> can demonstrate that planet-sized objects are thicker than fleas on a dog
> (i.e., my extrapolation wildly underestimates the number of these bodies
> by several orders of magnitude).

Do we actually have strong limits on the total mass
of our own Oort cloud?

(Of course it should be in the order of one solar mass
if together with similar clouds around stars it were to
influence the rotation curve. So how unlikely is that?)

--
Jos

[jacobnavia]

Le 16/07/2015 22:24, Jos Bergervoet a écrit :
> Do we actually have strong limits on the total mass
> of our own Oort cloud?

That is the problem. We know very little actually.

A new star was discovered not long ago, I reported that in this newsgroup.

<quote>
Images from the space telescopes also pinpointed the object's distance
to 7.2 light-years away, earning it the title for fourth closest system
to our sun. The closest system, a trio of stars, is Alpha Centauri, at
about 4 light-years away.
<end quote from

http://www.nasa.gov/jpl/wise/spitzer-coldest-brown-dwarf-20140425

>
That is a huge object just SEVEN LIGHT YEARS AWAY!

It is frozen cold, an old brown dwarf that has cooled to -48 Centigrade.
We detected it because even at that temperature, it shines in the
infrared and Spitzer saw it. It is one of the CLOSEST stars to the sun,
right after alpha centauri system.

And how do we detect those that are further away and cooled to maybe
-150 centigrade?

Really dark matter at those temperatures in the middle of integalactic
space...

We know nothing about deep space actually. The number of those objects
could be big.

And the comets?

As Mr Bergervoet said:

> Do we actually have strong limits on the total mass
> of our own Oort cloud?

New Horizons is going there now, having passed Pluto. Would the mass of
the cloud interfere with the flight path of the spacecraft?

Can the mass and speed of the spacecraft (that we can know very well)
allow us to detect hidden masses that change the path?

Or all those influences get destroyed by spacecraft movements to point
the antenna or whatever?

After transmitting the data, the spacecraft will go into hibernation,
and subtle influences of gravitational forces could be (maybe) measured
by determining the speed vector changes before/after hibernation with
high precision.

Or am I completely wrong?

[[Mod. note -- I think New Horizons is planning a flyby of one
Kuiper-belt object, and that flyby will probably give us a mass
measurement for that object. Apart from that, it's very unlikely that
New Horizons will come close enough to any other Kuiper-belt objects
(they're *very* far apart!) for them to have a detectable influence
on NH's trajectory. NH won't reach the Oort cloud in any of our
lifetimes.
-- jt]]

[Nicolaas Vroom]

Op donderdag 16 juli 2015 22:24:07 UTC+2 schreef Jos Bergervoet:

> On 7/16/2015 3:38 AM, Gary Harnagel wrote:
>
> > Yes, there is a real deficit problem unless the microlensing technique
> > can demonstrate that planet-sized objects are thicker than fleas on a dog
> > (i.e., my extrapolation wildly underestimates the number of these bodies
> > by several orders of magnitude).
>
> Do we actually have strong limits on the total mass
> of our own Oort cloud?
>

Maybe there are more questions.
The first question is slightly different:
What is the shape of the Oort Cloud ?
When you study the shape and size of Oort cloud
in: https://en.wikipedia.org/wiki/Oort_cloud than you can see
that its inner radius is small compared to its outer radius
which is 10 times as large.

The next question to answer is what is the mass of three times
the inner radius multiplied by the average density of the Oort
Cloud
When this number is more or less the same you get an impression
of how much baryonic matter there is in the Oort Cloud.

The third question is:
Is there really an Oort Cloud around each star with empty
space between the Oort Cloud of each star.
It is easy possible that this huge region is not empty which
can inhabitate a lot of mass.

> (Of course it should be in the order of one solar mass
> if together with similar clouds around stars it were to
> influence the rotation curve. So how unlikely is that?)
>
> --
> Jos

The numbers should demonstrate the verdict.

Nicolaas Vroom

[Nicolaas Vroom]

Op vrijdag 17 juli 2015 10:00:41 UTC+2 schreef jacobnavia:

>
> We know nothing about deep space actually. The number of those objects
> could be big.
>

And what about smaller objects?

The question of course is should we not first study
and solve (which means ?) this issue before we start
introducing a new kind of matter called darkmatter
which include dark forces (pos and neg), dark photons, dark
electromagnetism, and all types of dark particles (light and heavy)

This whole concept of dark photons is the more strange because the major
difference is that we humans can only detect type 1 but not type 2 (dark).
while in principle it is a physical issue.
In fact the whole space surrounding me is filled with photons type 1.
What happens when a type 2 photon enters in my room is a mystery.
Accordingly to the SAm article there is a clear difference between
type 1 matter and type 2 matter in the disc (proposal).
That means type 1 is in the spiral arms and type 2 (dark) outside the
spiral arms (which make the galaxy elliptical).
How this clear distinction is reached or obtained (specific after a galaxy
merge or collision) is also a mystery.

A universe consisting of almost only baryonic matter is much simpler.
(that leaves the door open of a universe consisting of only dark matter)

Nicolaas Vroom

[Gary Harnagel]

On Saturday, July 18, 2015 at 11:37:18 PM UTC-6, Nicolaas Vroom wrote:
>
> Op donderdag 16 juli 2015 22:24:07 UTC+2 schreef Jos Bergervoet:
> > On 7/16/2015 3:38 AM, Gary Harnagel wrote:
> >
> > > Yes, there is a real deficit problem unless the microlensing technique
> > > can demonstrate that planet-sized objects are thicker than fleas on a dog
> > > (i.e., my extrapolation wildly underestimates the number of these bodies
> > > by several orders of magnitude).
> >
> > Do we actually have strong limits on the total mass
> > of our own Oort cloud?
>
> Maybe there are more questions.
> The first question is slightly different:
> What is the shape of the Oort Cloud ?
> When you study the shape and size of Oort cloud
> in: https://en.wikipedia.org/wiki/Oort_cloud than you can see
> that its inner radius is small compared to its outer radius
> which is 10 times as large.
>
> The next question to answer is what is the mass of three times
> the inner radius multiplied by the average density of the Oort
> Cloud
> When this number is more or less the same you get an impression
> of how much baryonic matter there is in the Oort Cloud.

Your link says the outer (spherical) Oort cloud has an estimated mass of
about five earths. The inner (donut shaped) cloud "should have tens or
hundreds of times as many cometary nuclei as the outer halo"

So maybe a few Jupiters in terms of mass? That still less than one per
cent of the solar mass.

> The third question is:
> Is there really an Oort Cloud around each star with empty
> space between the Oort Cloud of each star.
> It is easy possible that this huge region is not empty which
> can inhabitate a lot of mass.

Your wiki link says the Oort cloud goes out two light years, which means
that huge region is not empty, but it has been accounted for (apparently)
in the five earth masses.

> > (Of course it should be in the order of one solar mass
> > if together with similar clouds around stars it were to
> > influence the rotation curve. So how unlikely is that?)
> >
> > --
> > Jos
>
> The numbers should demonstrate the verdict.
>
> Nicolaas Vroom

It appears to me that even with there being more and more stuff at smaller
and smaller diameters throughout interstellar space, their volumes (and
therefore their masses) goes as 1/r^3, so the maximum mass fraction occurs
at the red dwarf/brown dwarf level. Not nearly enough to account for dark
matter.

Gary

[Jos Bergervoet]

On 7/19/2015 5:47 PM, Gary Harnagel wrote:
> On Saturday, July 18, 2015 at 11:37:18 PM UTC-6, Nicolaas Vroom wrote:
>> Op donderdag 16 juli 2015 22:24:07 UTC+2 schreef Jos Bergervoet:
>>> On 7/16/2015 3:38 AM, Gary Harnagel wrote:
>>>
>>>> Yes, there is a real deficit problem unless the microlensing technique
>>>> can demonstrate that planet-sized objects are thicker than fleas on a dog
>>>> (i.e., my extrapolation wildly underestimates the number of these bodies
>>>> by several orders of magnitude).
>>>
>>> Do we actually have strong limits on the total mass
>>> of our own Oort cloud?
>>
>> Maybe there are more questions.
>> The first question is slightly different:
>> What is the shape of the Oort Cloud ?
>> When you study the shape and size of Oort cloud
>> in: https://en.wikipedia.org/wiki/Oort_cloud than you can see
>> that its inner radius is small compared to its outer radius
>> which is 10 times as large.
>>
>> The next question to answer is what is the mass of three times
>> the inner radius multiplied by the average density of the Oort
>> Cloud
>> When this number is more or less the same you get an impression
>> of how much baryonic matter there is in the Oort Cloud.
>
> Your link says the outer (spherical) Oort cloud has an estimated mass of
> about five earths.

That statement is accompanied by "assuming that Halley's Comet
is a suitable prototype for comets within the outer Oort cloud"
And in the same paragraph concludes by saying that we nowadays
have "lower estimates" than some time ago.

So that's why I asked if we have any strong limits at all!

...

> It appears to me that even with there being more and more stuff at smaller
> and smaller diameters throughout interstellar space, their volumes (and
> therefore their masses) goes as 1/r^3, so the maximum mass fraction occurs
> at the red dwarf/brown dwarf level.

Unless the numerical abundance goes up faster than 1/r^3 for
even smaller r. So the question remains: how is all this
restricted by experimental limits (from e.g. microlensing, or
extinction effects anywhere in the EM or particle spectrum?)

--
Jos

[[Mod. note -- The typical comet in the outer Oort cloud has never
(yet) had a close passage by the Sun. So Halley's Comet (which has
had ~25 observed passages, and probably many more before the first
recorded observations), is unlikely to be "typical".
-- jt]]

[Nicolaas Vroom]

Op zondag 19 juli 2015 17:47:09 UTC+2 schreef Gary Harnagel:

>
> Your link says the outer (spherical) Oort cloud has an estimated
> mass of about five earths.

One important document I have studied is document 3 which is mentioned
often in https://en.wikipedia.org/wiki/Oort_cloud

[[Mod. note -- I think the author is referring to
Morbidelli,
"Origin and Dynamical Evolution of Comets and their Reservoirs"
http://arxiv.org/abs/astro-ph/0512256
-- jt]]

My understanding was that the Oort Cloud contains the building blocks
of the creation of the Sun and the planets. This process continues in
the form of planets.
At the same time these same building blocks can also form larger objects
which stay inside the Oort Cloud.
Document 3 gives a much more complex description in chapter 4.
"Imagine an early time when the Oort cloud was still empty and the giant
planets' neighborhoods were full of icy planetesimals." etc.
A typical sentence in this document is at page 44:
"This requires that Jupiter and Saturn were more effective in the real
Oort cloud building process than in the simulations of [30]"
The bottom part of page 44 is important starting with: "The way out"

The document does not mention darkmatter.
To include darkmatter in this document makes everything much more complex.
Specific you have to mentioned how much dm there is in the Oort Cloud
and almost everything related to Chapter 4.

In theory there are Oort clouds around each star. Document 3 mentions
that also. See for example page 30.
The inter-Oort-cloud-space defines all space outside these Oort clouds
The question is what are its constituents ie its composition.
Its small objects are all invisible.
Is that baryonic matter or are that Wimp's or wimpsicals?

> > The third question is:
> > Is there really an Oort Cloud around each star with empty
> > space between the Oort Cloud of each star.
> > It is easy possible that this huge region is not empty which
> > can inhabitate a lot of mass.
>
> Your wiki link says the Oort cloud goes out two light years, which means
> that huge region is not empty, but it has been accounted for (apparently)
> in the five earth masses.

The Oort cloud goes to 50000 AU in document 3, based on simulations.
See page 31. I did not check the 2 ly.
IMO what is outside this 50000 AU is not accounted for.
Document 3 is highly based on simulations. In principle there
is nothing wrong with this.
These simulations for example can be very convincing if they show
the right masses and distributions of our solar system but at the same
time it does not mean that their predictions are correct towards
on the mass and size of the Oort Cloud if not confirmed by observations.
And this last part is very difficult.

> It appears to me that even with there being more and more stuff at
> smaller and smaller diameters throughout interstellar space, their
> volumes (and therefore their masses) goes as 1/r^3, so the maximum mass
> fraction occurs at the red dwarf/brown dwarf level. Not nearly enough to
> account for dark matter.
>
> Gary

When you study the 1992 article you can see that the total number of Red
and White dwarfs is much larger than the K dwarfs.
For the amount of mass the same logic applies.
My reasoning is that the R and W dwarfs are like the building blocks
for the K dwarfs and the K dwarfs are the building blocks the G stars etc.
What is missing are the building blocks of the R and W dwarfs.

The 1992 article at the end reads: "For these reasons we know that the
universe has more dark matter than luminous matter. But no one knows
what dm is. It could be faint stars, like R and W dwarfs or it could be
subatomic particles. Whatever it is dm may be the Grand Illusion in its
most sinister incarnation: the universe is full of something that our
instruments cannot see"

The SA article writes:
In addition to the normal "baryonic" matter in the cosmos, some hidden
form of matter matter must be out there, gravitationally tugging on
galaxies to keep them spinning as fast as they do and holding galaxies
together.
IMO let us first stictly investigate our own galaxy the Milky Way
and come to an agreement what the solution of the dm issue is.
This is already difficult enough.
Do we need any dm? If so how much and where should it be?
Inside the disc or outside the disc or both?
If inside the disc where? etc
Reading document 3 this whole picture becomes more complex.

Nicolaas Vroom.