Do U wana see Dark Matter ???

Look at the picture. The Dark Matter is clearly visible; And U humans r not even aware of it.
<img src="http://www.sciforums.com/attachment.php?attachmentid=3394&stc=1"></img>

 

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Nice picture,
But strangly enough the Wilkinson Microwave Anisotropy Probe ( WMAP) has been detecting microwave radiation all over the sky from a vantage point 1.5 million kilometres (930,000 miles ) from Earth, at the quasi-stable L2 Lagrange point. Its purpose is to study the cosmic microwave background, or CMB, which is the `echo` of the Big Bang.
According to WMAP scientists, non-cosmological microwaves could come from ionised hydrogen in our own Milky Way Galaxy, interstellar dust, and from the <b>fast electrons</b> found in supernova remnants.
And they have found an <i>unexplainable haze</i> that surrounds the centre of <b>our galaxy</b>, extending out to about 20º on the sky. The radiation looks like what ionised hydrogen atoms emit , but there aren't enough of those around. It also looks like what would be emitted by fast electrons in a magnetic field — but they would have to be moving near the speed of light.

A new theory suggests that these observations are the signature of dark-matter ; or rather the of annihilation darkmatter `antiparticle`. The annihilation of an `anti-neutrino` ; these neutralinos creates other particles — including pions, electrons, and positrons — that can attain near light speeds. When moving through a magnetic field, fast-moving charged particles emit synchrotron radiation of exactly the kind WMAP has detected. It is also interesting the microwave excess increases toward the centre of our galaxy nicely match the expected distribution of dark matter.

"<i>If it turns out the haze results from dark-matter annihilation, that would be a major breakthrough in understanding what dark matter is</i>."

http://www.shef.ac.uk/physics/idm2004/talks/thursday/pdfs/finkbeiner_douglas.pdf

 

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RawRhinkTank.
The dark lanes are dust clouds of varying compositions and makes this one of the greatest space images. Dark mater is not dark and maybe it should be called invisible mater, the only way we know it exists is by the motion of material around galaxies. The stars and dust orbit the galaxies faster then the mass of the visible material can account for. Hence there is something there that cant be seen (dark mater).

 

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That is not dark matter, we all know that dark matter is waste from a 3 eyed critter named Nibbler.

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It is defenitely not dark matter. Dark Matter- if it exist-
is defined as dark, meaning invissible. So let us get on to annother subject.

 

Its Dark Matter, No doubt on it.

This matter must be remnants of old stars ie. They must be cold stars.

Dead cold stars , how do U all think will U detect them if there is no light from them ?
And how many Cold stars should there be by now since start of stars in the universe ?

 

Hum, cold dead stars are made from baryonic matter, i think tht it has been shown that the universe has only about 4% of this `normal` matter.
The rest is , er, something else...non-baryonic matter.
http://map.gsfc.nasa.gov/m_uni/uni_101matter.html

"<i>23% Cold Dark Matter, 73% Dark Energy. Thus 96% of the energy density in the universe is in a form that has never been directly detected in the laboratory. The actual density of atoms is equivalent to roughly 1 proton per 4 cubic meters.</i>"

 

I may be wrong, but hasn't the dark matter been accounted for by adding the angular (orbital) momentum of all the stars in the universe???

 

Definitions of Dark matter on the Web:

The matter which is postulated to account for at least 90% of the mass of the Universe, but which has yet to be directly detected. The evidence for its existence comes mainly from observations of the dynamics of stars in galaxies and of galaxies in clusters of galaxies, from gravitational lensing and from cosmological models. Candidates for dark matter range from brown dwarfs and black holes to weakly-interacting elementary particles such as low-mass, fast-moving neutrinos or massive, slow-moving cold dark matter particles.
www.pparc.ac.uk/Ps/Psc/Gl/glossary.asp


Material that is believed to make up more than 90% of the mass of the universe, but is not readily visible because it neither emits nor reflects electromagnetic radiation, such as light or radio signals. Its composition is unknown.
www.genesismission.org/glossary.html


Theoretical non-luminous matter that has eluded detection by all present means, except through gravitational interaction with luminous objects. Astronomers and astrophysicists calculate that dark matter comprises more than 90 percent of the universe. Perhaps most of the universe exists as undetected clumps of interstellar dust and gas, plus cold dark stellar cores that collapsed billions of years ago. Others have suggested an unknown form of matter, and a small mass for neutrinos. Whatever the explanation, much of the universe has yet to be seen.
stardate.org/resources/astroglossary/glossary_D.html


–The apparently dominant form of matter in the Universe, perhaps accounting for more than 90 percent of the total mass. Unlike “normal” matter, it does not form stars and galaxies; hence, there is no mechanism for producing the radiation with which dark matter might be directly seen.
www.pa.msu.edu/soarmsu/glossary.htm


A term used to describe matter in the universe that cannot be seen, but can be detected by its gravitational effects on other bodies.
www.seasky.org/astronomy/sky1a.html


Matter that's thought to exist in the universe, but that emits no signals other than gravitational effects.
whyfiles.org/017planet/glossary.html


Mass whose existence is deduced from the analysis of galaxy rotation curves and other indirect evidence but which has so far escaped direct detection.
universe.gsfc.nasa.gov/resources/glossary.html


material that does not emit any light (or not detected yet), but has a significant gravitational effect.
www.astronomynotes.com/glossary/glossd.htm


Invisible "cosmic glue" that holds together rapidly spinning galaxies and controls the rate at which the universe expands. It is observed by watching its gravitational affect on other objects.
library.advanced.org/26220/glossary/


A nonluminous gravitational component of the universe invoked to explain the internal motions of galaxies and the motions of galaxies within clusters of galaxies.
www-glast.sonoma.edu/scitech/gru/glossary.htm


Any nonluminous astronomical object or particle that is detected only by its gravitational influence. Examples include planets, black holes, white dwarfs (because they are low luminosity) and more exotic things like weakly interacting particles (WIMPs).
wwwmain.cv.nrao.edu/imagegallery/glossary.shtml


the "missing" mass of the Universe known to exist because more mass than can be observed is needed for a universe of ours' size and stability, possibly in the form of small black holes, particles currently thought to be massless, or mass exerting gravitational forces fourth-dimensionally
people.ucsc.edu/~erowland/glossary.html

 

Guess there's not much I can add to that! Thankyou, CosmicTraveller...

The baryonic forms of dark matter (MACHOs, and dark substellar objects in the disk of our galaxy) have been detected, but so far in vastly insufficient numbers to make up 23% of the apparent mass-density of the Universe. What we're seeing in that beautiful photo of M104 is definitely dust: the Milky Way might look similar, from an appropriate external viewpoint, except that the disc would be less rigidly defined.

Hypothetical non-bayonic dark matter (WIMPs, axions, photinos etc) continue to elude detection despite decades of hopeful experiments. Either the theories which predict their properties are grossly incorrect, or they are somehow concentrated in specific parts of galaxies which exlude our own location - or they don't exist at all, and the mechanics of gravitation on an intergalactic scale are subtly different from Newtonian or Relativistic frameworks.

 

Thanks Blobrana, Cosmictraveler

how many Cold stars should there be by now since start of stars in the universe ?

If Universe is 13 billion years old, And average age of a star is 10 Billion years then most of the stars formed at the beginning must be cold by now ??? That answer depends on how much of the universe formed into stars in the beginning specially when universe was much denser than today.

 

What can we say? A dark matter is a thing which fully absorbs or fully emits everything it comes across, so it can be one since it's so bright, or not yet...

 

Actually, the vast majority of stars are much smaller than our Sun, and hence (paradoxically) their lives are far longer. Every K or M-class dwarf with less than about 0.75 Solar mass which ever formed will still be shining today, even if they were born only a million years or so after the Big Bang. As such, they do not constitute dark matter. The smallest ones can, in fact, continue shining for 10-100 trillion years - their stories have barely begun.

Really massive, short-lived stars - as well as being comparatively rare - tend to lose most of their mass whilst dying as supernovae; only a small fraction of their original matter will become part of a dark, dense stellar remnant, whilst the rest is recycled into new stars.

 

Thanks Starthane Xyzth
That was interesting
so is this 0313-192 galaxy, soorry all U blind humans
<img src="http://www.astr.ua.edu/keel/research/acs0313d.jpg"></img>

 

http://kingpin.ucsd.edu/~howk/EdgeOns/n4013.html

THE NGC 4013

U see a single pixel on this pictures are stars, so now compare the size of the dust.

The dust U can see is due to the obstructions but what about the dusts obstructed by the stars ?


<img src="http://www.spacetelescope.org/images/screen/opo0107a.jpg"></img>

 

Hum,
well, to work out how much matter there is, (i won`t got into technicalities, but) i believe that the The Keck telescope in Hawaii, was able to show that extremely distant galaxies, far away across the Universe, contain much more deuterium than the stars of our Galaxy do.
It might see a rather exotic/pointless discovery; But the intresting bit is that deuterium (er, heavy hydrogen) was made in the Big Bang, but <b>cannot</b> be made inside stars. In fact, stellar processes destroy it.
We know how much deuterium there is in stars and galaxies by measuring the light spectrum it leaves a characteristic fingerprint in the spectral lines. Because light from very distant galaxies takes a long time to reach us (sometimes, billions of years) they are seen as they were long ago.
Spectroscopic measurements of the amount of deuterium (or lithium can be used) in distant galaxies are <b>the same</b> as measuring the amount of deuterium around when the Universe was young.
<b>
The standard calculations of what happened during the Big Bang, the amount of deuterium around is very closely tied to the <i>total amount of atomic matter created</i>. (yeah, the universe was more dense) The more deuterium there is the less atomic matter there can be overall. </b>


This finding was confirmed by Researchers analysing data obtained by NASA's Far Ultraviolet Spectroscopic Explorer, or FUSE. The abundance of deuterium, in the Milky Way galaxy today also showed a consistent pattern that can be simply explained.

The total ratio of deuterium to hydrogen in gas between stars (out to 3,000 light years from the sun) is 23 parts per million. That ratio is still only slightly smaller than the best estimates of the ratio at the beginning of the universe, which was probably about 28 parts per million.
So using the new figures, of deuterium abundances, the Big Bang could have produced barely enough baryonic matter to make the stars we see today, and no room for MACHOs.
A ball park figure i guess is about 10⁸⁰ atoms for the observable universe

The inference is that any darkmatter around must be in the form of WIMPs or something equally strange.

hope that helps.

< edited for clarity>

 

We cannot see dark matter, therefore, that disk in the middle of the Sombrero galaxy is not dark matter.

It's interstellar dust and gas. The reason why it looks so dense is exactly the reason why the enormity of galaxies is so vastly underestimated.

 

To quote Gotti: It's like mind over matter, if you don't mind, it don't matter

According to some, dark matter is dark and nearly invisible because it is associated with matter in other dimensional planes/branes and only makes its presence aware by gravitons wich are according to new theories might be able to roam more freely between branes (wich would explain why gravity is such a weak force, it is actually not weak, but its power is diluted over several dimensions)

If we map the gravitons with the new gravity wave detectors, we could be actually mapping universes in other planes...?

 

So, you think that star formation is more or less finished already - or that there is no "juvenile" interstellar medium out there for new stars, only recycled gas from previous stellar generations? The amount of cold hydrogen detected by 21-cm radio emission from all over the Galaxy would seem to disagree. Not to mention that diffuse X-ray emissions from large clusters of galaxies indicate that vast quantities of ionized intergalactic hydrogen must be present within those clusters. Mainstream astronomers generally believe that star formation can continue for another 1-10 trillion years yet. At least, I hope the stellar-genic era isn't already drawing to a close - or, relatively soon in cosmic terms, nothing will shine but feeble red dwarfs, and Earth's night sky will be almost blank. The Universe will be a gloomy and depressing place indeed, and only grow gloomier over time.

@Vortexx: this could tie in with another recent thread:

http://www.sciforums.com/showthread.php?p=705467#post705467

 

LOL!

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