Milky Way Appears to be Void of Dark Matter

Milky Way Appears to be Void of Dark Matter --"The Mystery of Dark Matter Deepens --A New Solution for the Missing Mass Problem Must be Found."
http://www.dailygalaxy.com/my_weblog/20 ... or-th.html

The most accurate study so far of the motions of stars in the Milky Way has found no evidence for dark matter in a large volume around the Sun. According to widely accepted theories, the solar neighbourhood was expected to be filled with dark matter, a mysterious invisible substance that can only be detected indirectly by the gravitational force it exerts.

A new study by a team of astronomers in Chile has found that these theories just do not fit the observational facts. This may mean that attempts to directly detect dark matter particles on Earth are unlikely to be successful.

Milky Way Appears to be Void of Dark Matter --"The Mystery of Dark Matter Deepens --A New Solution for the Missing Mass Problem Must be Found."
http://www.dailygalaxy.com/my_weblog/20 ... or-th.html

The most accurate study so far of the motions of stars in the Milky Way has found no evidence for dark matter in a large volume around the Sun. According to widely accepted theories, the solar neighbourhood was expected to be filled with dark matter, a mysterious invisible substance that can only be detected indirectly by the gravitational force it exerts.

A new study by a team of astronomers in Chile has found that these theories just do not fit the observational facts. This may mean that attempts to directly detect dark matter particles on Earth are unlikely to be successful.

Odd. Steve Allen, a mere few years ago, was able to see them everywhere.

Of course Milky Way is void of Dark Matter.

It uses milk chocolate, not dark chocolate.

Get a Milky Way Dark instead.

Somebody should turn on a light.

Anybody look in the White House?

For His Dark Materials?

Astronomers from the University of Bonn in Germany have discovered a vast structure of satellite galaxies and clusters of stars surrounding our Galaxy, stretching out across a million light years. The work challenges the existence of dark matter, part of the standard model for the evolution of the universe.

Snip

Conventional models for the origin and evolution of the universe (cosmology) are based on the presence of 'dark matter', invisible material thought to make up about 23% of the content of the cosmos that has never been detected directly. In this model, the Milky Way is predicted to have far more satellite galaxies than are actually seen.

Snip

"Once we had completed our analysis, a new picture of our cosmic neighbourhood emerged," says Pawlowski. The astronomers found that all the different objects are distributed in a plane at right angles to the galactic disk. The newly-discovered structure is huge, extending from as close as 33,000 light years to as far away as one million light years from the centre of the Galaxy.

http://www.sciencedaily.com/releases/20 ... 094352.htm

ahem.
at the moment, the UNIVERSE appears void of "dark matter"
this pet invisible pink unicorn of the Grand Unification crowd annoys me.

ahem.
at the moment, the UNIVERSE appears void of "dark matter"
this pet invisible pink unicorn of the Grand Unification crowd annoys me.

Universe and Galaxy have not been interchangeable words since the Hubble expansion was discovered.

ahem.
at the moment, the UNIVERSE appears void of "dark matter"
this pet invisible pink unicorn of the Grand Unification crowd annoys me.

It's phlogiston all the way down.

ahem.
at the moment, the UNIVERSE appears void of "dark matter"
this pet invisible pink unicorn of the Grand Unification crowd annoys me.

Universe and Galaxy have not been interchangeable words since the Hubble expansion was discovered.

no shit.
however, as this galaxy is a subset of the universe, and the universe is void of these pet invisible pink unicorns...
get the point?

as this galaxy is a subset of the universe, and the universe is void of these pet invisible pink unicorns...
get the point?

Sure.

But consider this:

The astronomers found that all the different objects are distributed in a plane at right angles to the galactic disk.

So, what I get from this is that this large structure is at right angles to the (Milky Way) Galaxy. And the Solar System is at right angles to the galactic disk.

And Uranus is at right angles to the Solar Ecliptic.

So ... who's got the right angle?

(Note: It's possible there's a Z-axis component involved here as well. The literature doesn't make that possibility or its exclusion clear.)

So, what I get from this is that this large structure is at right angles to the (Milky Way) Galaxy. And the Solar System is at right angles to the galactic disk.

And Uranus is at right angles to the Solar Ecliptic.

So ... who's got the right angle?

I believe it was Stephen Hawking,
or it might have been Keith Richards,
who said, "If it was up Uranus, you'd know."

You can get them dark nowadays:

I think the word this thread is looking for is "devoid."

Some of the oldest galaxies in the Universe have three times more stellar mass, and so many more stars, than all current models of galaxy evolution predict.

The finding comes from the Atlas3D international team, led by an Oxford University scientist, who found a way to remove the 'halo' of dark matter that has clouded previous calculations.The team's analysis means that all current models, which assumed for decades that the light we observe from a galaxy can be used to infer its stellar mass, will have to be revised.

It also suggests that researchers have a new riddle to ponder: exactly how galaxies forming so early in the life of the Universe got to be massive so fast.

http://www.sciencedaily.com/releases/20 ... 211411.htm

Some of the oldest galaxies in the Universe have three times more stellar mass, and so many more stars, than all current models of galaxy evolution predict.

The finding comes from the Atlas3D international team, led by an Oxford University scientist, who found a way to remove the 'halo' of dark matter that has clouded previous calculations.The team's analysis means that all current models, which assumed for decades that the light we observe from a galaxy can be used to infer its stellar mass, will have to be revised.

It also suggests that researchers have a new riddle to ponder: exactly how galaxies forming so early in the life of the Universe got to be massive so fast.

http://www.sciencedaily.com/releases/20 ... 211411.htm

It's the sedentary lifestyle that packs on the extra weight.

We know about dark matter from the motions of stars in our galaxy. This report says that when you perform a similar measurement with just the local stars, you don't see the same behavior.

So it seems to me that the issue here has nothing to do with dark matter per se, but that two measurements of the same general type are not consistent with each other.

We know about dark matter from the motions of stars in our galaxy.

Uhm, no.

Remarkably, it turns out there is five times more material in clusters of galaxies than we would expect from the galaxies and hot gas we can see. Most of the stuff in clusters of galaxies is invisible and, since these are the largest structures in the Universe held together by gravity, scientists then conclude that most of the matter in the entire Universe is invisible. This invisible stuff is called 'dark matter', a term initially coined by Fritz Zwicky who discovered evidence for missing mass in galaxies in the 1930s.

http://imagine.gsfc.nasa.gov/docs/scien ... atter.html

Actually, yes.

Dark matter came to the attention of astrophysicists due to discrepancies between the mass of large astronomical objects determined from their gravitational effects, and mass calculated from the "luminous matter" they contain; such as stars, gas and dust. It was first postulated by Jan Oort in 1932 to account for the orbital velocities of stars in the Milky Way and Fritz Zwicky in 1933 to account for evidence of "missing mass" in the orbital velocities of galaxies in clusters.

http://en.wikipedia.org/wiki/Dark_matter

Maybe it's patchy. Like clusters of dead brown-dwarf stars. Ordinary matter that's just too dim to show up on our detectors.

Maybe it's patchy. Like clusters of dead brown-dwarf stars. Ordinary matter that's just too dim to show up on our detectors.

Here's an older picture of the distribution: http://www.cfht.hawaii.edu/News/Lensing/

I don't know if this distribution is consistent with clusters of dead stars (the Forest Lawn Distribution?)

Maybe it's patchy. Like clusters of dead brown-dwarf stars. Ordinary matter that's just too dim to show up on our detectors.

The presence of that much ordinary matter would change the relative abundances of the light nuclei from what we observe them to be. While there may be some baryonic dark matter out there, it can't be enough to explain the observations.

Maybe it's patchy. Like clusters of dead brown-dwarf stars. Ordinary matter that's just too dim to show up on our detectors.

The presence of that much ordinary matter would change the relative abundances of the light nuclei from what we observe them to be. While there may be some baryonic dark matter out there, it can't be enough to explain the observations.

Which would be a greater departure from the present level of understanding: discovery of some more baryonic matter that we just haven't observed in the past, which would force adjustment of our rankings of the relative abundances of the elements, or, discovery of the same amount of mass but in some previously unknown, non-baryonic form? I realize that either discovery would probably drive some re-thinking, I'm just wondering which would be the more major shift, in terms of overall disruption of previous understanding.

Which would be a greater departure from the present level of understanding: discovery of some more baryonic matter that we just haven't observed in the past, which would force adjustment of our rankings of the relative abundances of the elements, or, discovery of the same amount of mass but in some previously unknown, non-baryonic form? I realize that either discovery would probably drive some re-thinking, I'm just wondering which would be the more major shift, in terms of overall disruption of previous understanding.

We can't adjust our rankings of the abundances of the elements. We measure those, and they rule out the hypothesis that dark matter is baryonic. It's not close; it's off by many sigma. You'd pretty much have to overthrow quantum mechanics to make it fit. Alternatively, you could overthrow General Relativity, and say that gravity simply behaves as if there's more mass than there really is. Ah, but then you wouldn't be able to explain this new measurement, which gets back to my first point.

It's not much of a stretch to imagine a particle we are as yet unable to detect. We've been there before: neutrinos come immediately to mind. (Turns out they have mass, too, but not all of their properties are consistent with what we know about dark matter.) It's not out of the question that dark matter could either be explained by an undiscovered Standard Model particle (e.g. the axion from quantum chromodynamics) or by a simple extension to the Standard Model (e.g. the lightest supersymmetric particle, which should be stable and very hard to detect).

Fifty years from now, the histories of particle physics will make it look like we knew what dark matter was all along, but simply had a hard time proving what everybody suspected. (Similarly, current histories of particle physics make it seem as if quantum field theory was the main current of the theory of particle physics from the 40's to the 70's, glossing over the fact that other models were overwhelmingly more popular until the "November Revolution" of 1974.)