Halo of hot gas found around the Milky Way

https://groups.google.com/forum/#!to...ws/QoducJjmaj0
.... to the tune of 100% of the visible mass.

There is a big chunk of Dark Matter no longer required, depending on distribution...

David A. Smith

On 24/09/2012 2:47 PM, dlzc wrote:
https://groups.google.com/forum/#!to...ws/QoducJjmaj0
... to the tune of 100% of the visible mass.

There is a big chunk of Dark Matter no longer required, depending on distribution...

Depends on how much "a big chunk" means. What percentage of Dark Matter
would it constitute? 10%, 20%, or 1%?

Yousuf Khan

Dear Yousuf Khan:

On Tuesday, September 25, 2012 5:29:20 PM UTC-7, Yousuf Khan wrote:
On 24/09/2012 2:47 PM, dlzc wrote:

https://groups.google.com/forum/#!to...ws/QoducJjmaj0
... to the tune of 100% of the visible mass.

There is a big chunk of Dark Matter no longer
required, depending on distribution...

Depends on how much "a big chunk" means. What
percentage of Dark Matter would it constitute?
10%, 20%, or 1%?

There was a paper on arxiv.org that discussed options. It said Dark Matter could be eliminated entirely, but something "special" would have to be done by the time we reached the rim.

Having a massive cloud out as far as this, is pretty special. Ultimately it is time for a new accounting, with all the information we have gained since the 1930s. Seems like the last 10 years alone has been phenomenal...

So in answer to your question, I don't know. I'd figure it is just another rather large straw for the Dark Matter camel to have to carry, and stab at 10%.

Couple this with more brown dwarves than expected, dust clouds reducing luminosity in "scaling wavelengths", non-linear luminosity with temperature (a hot center is brighter, with less mass), and now this cloud... and I'd figure we can give up on Dark Matter existing at all inside the disk of a spiral galaxy. Or at least this one.

David A. Smith

On 25/09/2012 9:01 PM, dlzc wrote:
Dear Yousuf Khan:

On Tuesday, September 25, 2012 5:29:20 PM UTC-7, Yousuf Khan wrote:
On 24/09/2012 2:47 PM, dlzc wrote:

https://groups.google.com/forum/#!to...ws/QoducJjmaj0


.... to the tune of 100% of the visible mass.

There is a big chunk of Dark Matter no longer required, depending
on distribution...

Depends on how much "a big chunk" means. What percentage of Dark
Matter would it constitute? 10%, 20%, or 1%?

There was a paper on arxiv.org that discussed options. It said Dark
Matter could be eliminated entirely, but something "special" would
have to be done by the time we reached the rim.

The "rim" of what? The galaxy's disk? The galaxy's halo? The Universe's
rim?

Having a massive cloud out as far as this, is pretty special.
Ultimately it is time for a new accounting, with all the information
we have gained since the 1930s. Seems like the last 10 years alone
has been phenomenal...

I think it's pretty special, but not so much because it may eliminate
the Dark Matter, but because it proves that galaxies have a large store
of gas that they can keep drawing on to replenish their depleting
nursery clouds, long into the future, probably for trillions of years
into the future, instead of dying out from a freezing death. Universe
will keep glowing for some longer time yet.

So in answer to your question, I don't know. I'd figure it is just
another rather large straw for the Dark Matter camel to have to
carry, and stab at 10%.

Couple this with more brown dwarves than expected, dust clouds
reducing luminosity in "scaling wavelengths", non-linear luminosity
with temperature (a hot center is brighter, with less mass), and now
this cloud... and I'd figure we can give up on Dark Matter existing
at all inside the disk of a spiral galaxy. Or at least this one.

Still the combination of this cloud (which might be categorized as a
type of pseudo-WIMP itself), and a renewed interest in MACHOs like the
brown dwarfs, may not be enough to unseat the search for new true WIMPs.
They need to discover the sterile neutrino to eliminate exotic WIMPs.

Yousuf Khan

Dear Yousuf Khan:

On Tuesday, September 25, 2012 7:36:34 PM UTC-7, Yousuf Khan wrote:
On 25/09/2012 9:01 PM, dlzc wrote:
On Tuesday, September 25, 2012 5:29:20 PM UTC-7, Yousuf Khan wrote:
On 24/09/2012 2:47 PM, dlzc wrote:

There is a big chunk of Dark Matter no
longer required, depending on distribution...

Depends on how much "a big chunk" means. What
percentage of Dark Matter would it constitute?
10%, 20%, or 1%?

There was a paper on arxiv.org that discussed
options. It said Dark Matter could be eliminated
entirely, but something "special" would have to
be done by the time we reached the rim.

The "rim" of what? The galaxy's disk? The
galaxy's halo? The Universe's rim?

The average spiral galaxy's rim.

....
Still the combination of this cloud (which
might be categorized as a type of pseudo-WIMP
itself), and a renewed interest in MACHOs
like the brown dwarfs, may not be enough to
unseat the search for new true WIMPs. They
need to discover the sterile neutrino to
eliminate exotic WIMPs.

http://iopscience.iop.org/1475-7516/2012/03/018
.... there'd have to be a whole bunch of them...

David A. Smith

On Sep 24, 11:47*am, dlzc wrote:
https://groups.google.com/forum/#!to...ws/QoducJjmaj0
... to the tune of 100% of the visible mass.

There is a big chunk of Dark Matter no longer required, depending on distribution...

David A. Smith

There's no shortage of mass, unless excluding aether.

I've estimated 5e55~5e56 kg that's available within a volumetric
sphere of 1e11 ly diameter. That's roughly suggesting at most 1e24 kg
per cubic light year, or roughly 1.18e-24 kg/m3.

In article ,
Yousuf Khan writes:
Still the combination of this cloud (which might be categorized as a
type of pseudo-WIMP itself)

Why would you think the cloud is WIMPs )or pseudo-WIMPs, whatever
those might be)? The cloud is radiating and absorbing X-rays and
therefore presumably baryonic.

As far as I can tell, the hot gas found might account for much or all
of the baryonic dark matter. (Presumably we'll have to start calling
the matter "X-ray gas" or something instead of "dark," but that's how
science moves on.) It doesn't change the overall recipe that has
about 4% of the Universe being baryonic matter.

There's a nice illustration at http://chandra.si.edu/photo/2012/halo/
and link to a brief discussion of the "missing baryon" problem, which
_may_ now be solved. However, measuring the mass of the X-ray gas is
not easy, and the result needs more evidence. If it turns out that
the X-ray gas is more than 3% or so of the critical density (stars
are 1%), then cosmology will have a problem. I don't think that's
the way to bet.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

On 28/09/2012 1:23 PM, Steve Willner wrote:
In ,
Yousuf writes:
Still the combination of this cloud (which might be categorized as a
type of pseudo-WIMP itself)

Why would you think the cloud is WIMPs )or pseudo-WIMPs, whatever
those might be)? The cloud is radiating and absorbing X-rays and
therefore presumably baryonic.

Well, until now it was invisible to our various scopes, but now we find
it's visible in some special regions of the X-ray range, thus
pseudo-WIMPs, i.e. mostly not interacting with light, thus the
electromagnetic field.

As far as I can tell, the hot gas found might account for much or all
of the baryonic dark matter. (Presumably we'll have to start calling
the matter "X-ray gas" or something instead of "dark," but that's how
science moves on.) It doesn't change the overall recipe that has
about 4% of the Universe being baryonic matter.

There's a nice illustration at http://chandra.si.edu/photo/2012/halo/
and link to a brief discussion of the "missing baryon" problem, which
_may_ now be solved. However, measuring the mass of the X-ray gas is
not easy, and the result needs more evidence. If it turns out that
the X-ray gas is more than 3% or so of the critical density (stars
are 1%), then cosmology will have a problem. I don't think that's
the way to bet.

Well, my money is with the Dark Matter turning out to be a modified
gravitational effect (Dark Energy too).

Yousuf Khan

Dear Yousuf Khan:

On Saturday, September 29, 2012 6:07:14 PM UTC-7, Yousuf Khan wrote:
On 28/09/2012 1:23 PM, Steve Willner wrote:

In ,
Yousuf writes:

Still the combination of this cloud (which might
be categorized as a type of pseudo-WIMP itself)

Why would you think the cloud is WIMPs )or
pseudo-WIMPs, whatever those might be)? The
cloud is radiating and absorbing X-rays and
therefore presumably baryonic.

Well, until now it was invisible to our various
scopes, but now we find it's visible in some
special regions of the X-ray range, thus
pseudo-WIMPs, i.e. mostly not interacting with
light, thus the electromagnetic field.

Well, this had been see before, as the "missing normal matter" between us and quasars. And WIMPs are not supposed to undergo friction, but this ionized gas will.

....
There's a nice illustration at
http://chandra.si.edu/photo/2012/halo/
and link to a brief discussion of the "missing
baryon" problem, which _may_ now be solved.
However, measuring the mass of the X-ray gas is
not easy, and the result needs more evidence.
If it turns out that the X-ray gas is more than
3% or so of the critical density (stars are 1%),
then cosmology will have a problem. I don't
think that's the way to bet.

Well, my money is with the Dark Matter turning
out to be a modified gravitational effect (Dark
Energy too).

They keep finding collections of baryonic matter, and there won't be any need for any Dark Matter (other than neutrinos). And Dark Energy is already the cosmological constant...

David A. Smith

On 30/09/2012 2:26 PM, dlzc wrote:
Dear Yousuf Khan:

On Saturday, September 29, 2012 6:07:14 PM UTC-7, Yousuf Khan wrote:
Well, my money is with the Dark Matter turning
out to be a modified gravitational effect (Dark
Energy too).

They keep finding collections of baryonic matter, and there won't be any need for any Dark Matter (other than neutrinos). And Dark Energy is already the cosmological constant...

David A. Smith

Well if Dark Energy is just the Cosmological Constant, then the question
would be why is there any Cosmological Constant at all, why it's this
value. Einstein just put it in as an afterthought.

Yousuf Khan