The first dark galaxy found?

[smalltalk]

A black cloud of hydrogen gas and supposedly exotic particles, devoid of stars was observed using the Arecibo radio telescope in Puerto Rico.

It appears to be rotating so fast it would fall apart unless it contains a strong, hidden source of gravity. The researchers therefore argue that the cloud must be at least 80 per cent dark matter, the hypothetical invisible substance whose gravity is supposed to explain why many objects in the cosmos move as fast as they do.


http://www.arxiv.org/abs/astro-ph/0310192
http://www.newscientist.com/news/news.jsp?id=ns99994272

 

[Riesstiu IV]

Sounds scary, ! On a more serious note, this is actually very interesting. I always thought dark matter existed in the voids between galaxies.

 

[Perfection]

Cool! I've heard many of these theories discussed before,

I just want to know how they observed it!

 

[Smidlee]

Originally posted by smalltalk [/i]

The researchers therefore ARGUE that the cloud must be at least 80 per cent dark matter...



I wonder what those researchers was arguing over ? how dark is the matter? or maybe why does it matter?

 

[Tassadar]

Some misunderstood here i think.

They didnt detect a huge cloud of dark matter, but they detect a high velocity HYDROGEN gas rotating around what is thaugh to be dark matter.

So the gravity center could be dark matter. If it was a black hole, then we will see x-ray around it, but its not the case. If it was a neutron star, then we will detect periodic flash of radio-wave but its not the case.

All that is detected, is rotating hydrogen gas ( radio-wave signature) around a dark ( no electro-magnetic emision) high gravity center.

 

[Archer 007]

Wow!

That is very impressive.

 

[polymath]

Cool, if true!

This dark matter problem is exceedingly irksome for astronomers. Like their equivalent of 'Einstein's constant'. Hopefully we can learn more about it from this.

 

[Bozo Erectus]

Originally posted by Tassadar
If it was a black hole, then we will see x-ray around it, but its not the case. If it was a neutron star, then we will detect periodic flash of radio-wave but its not the case.

X-rays are created when matter is ripped apart as it approaches the black hole, right? So what I dont understand is: if this dark matter thing at the center of the cloud is a high density, high gravity object like a black hole, why arent x-rays created as matter interacts with it? If the matter isnt being ripped apart like with a black hole, whats happening to it?

 

[polymath]

@Dumb pothead
The dark matter isn't 'like a black hole'. The only thing 'like a black hole' is another black hole.

Dark matter is called dark matter because we can't detect it, but in order for astronomers to make their sums add up (regarding gravity and the mass of the universe) it was necessary to postulate it's existence. And this finding could show that they were right, i.e. that there exists a large mass of matter in the universe previously unaccounted for because it was not readily detectable.

So it's very good news for theorists!

 

[Gothmog]

Dark matter is necessary to explain the radial velocities of most visible galaxies in terms of newtonian gravity. It makes sense that there would be dark matter galaxies that form in the same way as visible matter galaxies, in fact there should be lots of these things since it seems that there is more dark matter than visible matter.

Tassadar laided out the evidence pretty well. It doesn't say anywhere that the thing at the center of the cloud is as high density as a black hole. Remember that for an external body gravity acts as if all the mass were at a singularity at the center of mass of the object doing the attracting.

I don't think we know enough about dark matter to say what would happen to some being 'consumed' by a black hole. But given that it doesn't absorb or emit radiation under normal circumstances, it probably wont when being 'consumed'. It simply doesn't have the necessary energetic transitions available to it.

 

[Tassadar]

Dumbpothead,

Like polymath said, the dark matter density is far from beeing like a black hole or a neutron star.

The dark matter have very low interactive propriety, I think some scientist call these matter WIMP, for weakly interacting massive particule.

I dont realy know what happen when normal matter fall on dark matter. Only indirect gravitational obervation allow astronomer to detect dark matter.

Other theory talk about gravitational breakthrough within parralel univers.

Here a link about a thread i start on dark matter and dark energy:http://forums.civfanatics.com/showthread.php?s=&threadid=64774

Edit: here is good info:http://www.lbl.gov/Science-Articles/Archive/Phys-HST-supernovae-sidebar1.html

 

[Bozo Erectus]

Originally posted by Gothmog
It doesn't say anywhere that the thing at the center of the cloud is as high density as a black hole.

Thats true, youre right about that. But whatever is at the center does have high gravity. The cloud is falling in to the dark matter center, more like a dark soup than a black hole? Theres no gamma rays either? Somethings going on in there, its probably emmiting some sort of radiation we arent aware of and cant detect.
@Tassadar-good call on the WIMPs. I had heard of them but definitely needed a refresher course, I googled this:

http://zebu.uoregon.edu/~soper/Mass/WIMPS.html

This one is a good explanation of dark matter, page 4 has the pros and cons of WIMPS being the dark matter:

http://chandra.harvard.edu/xray_astro/dark_matter.html

 

[Tassadar]

Dumbpothead,


The solution to the dark matter problem may well involve something very close to a parallel universe.


From your link:http://chandra.harvard.edu/resources/faq/dmatter/dmatter-9.html

 

[Bozo Erectus]

So the dark matter is like a shadow universe thats out there but doesnt interact with us except for gravity. If it has gravity then it has mass (bear with me, Im trying to wrap my brain around this stuff). So regular matter can get sucked into it but it wont interact with it? How fast does the matter get pulled in? Could you fly a vehicle into it, since it wouldnt interact with it?

 

[Gothmog]

Yes, tough to get your mind around this stuff. We know much about radiation and would detect any high energy stuff, at the low end it would have to be very vary large wavelength for us not to detect it and so would have a tough time carrying off all the resultant energy - and violate the blackbody standard - but not totally impossible afaik.

As I say above most visible galaxies are spinning too fast at their outer reaches to be supported by newtonian gravity and the visible matter. That was the first evidence for dark matter. So it does have to interact in terms of gravity, but doesn't have to have a very high density to have a large effect. That is why I mentioned the center of mass argument. If there were nuclear interactions of the type we understand there would be high energy radiation. Same for electrostatic interactions.

 

[Tassadar]

In order to explain the motions of the stars and galaxies, it must be spread out throughout the individual galaxies, and beyond, so that a more appropriate view would be of a galaxy embedded in a large invisible ball of dark matter.


This is from a previous link. I did some then and come up with this.


Those parralel univers are like very very small closed loop, gravity only can escape the loop, while normal matter cant breach the border of the loop neither electromagnetic wave. Edit: When a black hole is born( Big star end of life) then those frontier can be broken.

So what i think is most of star if not all, hoste one of those close loop, thats why the hydrogen is condensed and start up thermonuclear reaction. The latest observation exactly talk about a rotating hydrogen gas around a gravity center. The gravity center is the very small parralel univers.

 

[smalltalk]

Originally posted by polymath
So it's very good news for theorists!

Somewhere in the links computer simulations of galaxy formation are mentioned. These simulations take account of dark matter distribution. The simulations give a number of dwarf galaxies that is four times higher that the number of dwarf galaxies that are known.

The newfound dark galaxy - remember: no stars in there - is proposed to be "the first observed representative of this population of missing objects".