First dark matter galaxy discovered

Original Source

A British-led team of astronomers have discovered an object that appears to be an invisible galaxy made almost entirely of dark matter - the first ever detected. A dark galaxy is an area in the universe containing a large amount of mass that rotates like a galaxy, but contains no stars. Without any stars to give light, it could only be found using radio telescopes. It was first seen with the University of Manchester's Lovell Telescope in Cheshire, and the sighting was confirmed with the Arecibo telescope in Puerto Rico. The unknown material that is thought to hold these galaxies together is known as 'dark matter', but scientists still know very little about what that is.

The presence of dark matter in the Universe can be inferred by looking at the rotation of galaxies and measuring how fast their visible components are moving. The amount of matter in a galaxy dictates the gravitational force needed to hold it together. Astronomers have seen galaxies where the material is moving so fast that they should fly apart - as they don't, there must be a stronger gravitational force acting than can be accounted for using visible matter. This has led astronomers to believe that there is more matter unseen - the mass of this 'dark matter' can be calculated from the gravitational force that must be acting to hold the galaxy together.

Dr Robert Minchin from Cardiff University is one of the UK astronomers who discovered the mysterious galaxy, named VIRGOHI21. He explains, "From the speed it is spinning, we realised that VIRGOHI21 was a thousand times more massive than could be accounted for by the observed hydrogen atoms alone. If it were an ordinary galaxy, then it should be quite bright and would be visible with a good amateur telescope."

The ellipse shows the region of sky where the dark galaxy was found - image taken by Cardiff Astronomers using the Isaac Newton Telescope on La Palma.

The whole galaxy-sized rotating disk consisting entirely of dark matter and a small amount of hydrogen atoms (no stars!).
There is definitely more in the universe than meets the eye - literally

[edit on 28-12-2009 by Maslo]

Very nice post friend S&F!

Huh.
I'm curious...
if that area contains mass and has an intense gravitational pull that's strong enough to create a containment field of some kind of matter, then why isn't it dense enough to block the light from the stars behind it, or at the very least cause light passing through it to bend around it's gravitational field and render it somewhat visible?
Because, honestly, I'm no physicist, but all I see is a bunch of stars.
Perhaps I'm missing something?
Interesting stuff though.

I wasn't aware that anybody has actually discovered "dark matter" itself.

And here they find a whole galaxy of it?

reply to post by Matthew Dark

The presence of dark matter in the Universe can be inferred by looking at the rotation of galaxies and measuring how fast their visible components are moving. The amount of matter in a galaxy dictates the gravitational force needed to hold it together. Astronomers have seen galaxies where the material is moving so fast that they should fly apart - as they don't, there must be a stronger gravitational force acting than can be accounted for using visible matter. This has led astronomers to believe that there is more matter unseen - the mass of this 'dark matter' can be calculated from the gravitational force that must be acting to hold the galaxy together.

It's not necessarily a mysterious "thing." It's just unaccounted for matter (presumably).

reply to post by Deny Arrogance


Yeah...y'know...
I was wondering the same thing myself.
At this point, I thought it was all just theory.
Good point.

It will be cool to meet the dark matter aliens from galaxy VIRGOHI21. But I guess we'll need infrared glasses to see them.

Originally posted by Ophiuchus 13
Very nice post friend S&F!

It is a nice find.
Dude, I just checked your profile because your avatar is so cool. I have a tattoo close to that design.
And I noticed that you picked yourself as a foe.
You foed yourself, dude?

To be honest that pic is a bit of a joke. It looks like someone has just drawn an elipse over some random picture of space with a weird line pointing to what seems to be an insignificant galaxy or star inside(or behind?) that elipse.

Or maybe thats just my untrained eyes, and a physicist could tell us otherwise.

Im not saying this is a fake or anything of the sort, just that the pic is bad.


As for the implications of this amazing discovery, it seems like our understanding of the universe is moving further and further away from the idea of it being an empty baron landscape, with only a tiny percentage filled by galaxies. And instead we find things like dark galaxies!!

What I'd really love to know however, is an estimate of roughly how many galaxies are dark compared to ...light in the universe. That data could massively change astro-physics.

great thread btw.

funny that you made this thread
I just made this today
www.abovetopsecret.com...

Perhaps there are no stars, but maybe there are Dark Stars!
Stars created by dark matter and therefore invisible!

So the question is.... is a star that is invisible till a star?

Also, this may or may not be relevant but IS interesting

As soon as an interaction between holographic dark energy and dark matter is taken into account, the identification of an IR cutoff with the Hubble radius H−1, in a flat universe, can simultaneously drive accelerated expansion and solve the coincidence problem. Based on this, we demonstrate that in a non-flat universe the natural choice for the IR cutoff could be the apparent horizon radius, . We show that any interaction of dark matter with holographic dark energy, whose infrared cutoff is set by the apparent horizon radius, implies an accelerated expansion and a constant ratio of the energy densities of both components thus solving the coincidence problem. We also verify that for a universe filled with dark energy and dark matter, the Friedmann equation can be written in the form of the modified first law of thermodynamics, dE = ThdSh + WdV, at the apparent horizon. In addition, the generalized second law of thermodynamics is fulfilled in a region enclosed by the apparent horizon. These results hold regardless of the specific form of dark energy and interaction term. Our study might reveal that in an accelerating universe with spatial curvature, the apparent horizon is a physical boundary from the thermodynamical point of view.

www.iop.org...=68257366.2/0264-9381/27/2/025007

What in the world is holographic dark energy?

I bet scientists are making wrong conclusions again... similar to ingenious conclusion about the cloud of dust Solar system is passing through 'that physics says should not exist.' link

also, I thought that dark matter is invisible, how can it be that it is visible in infra red suddenly?

Originally posted by donhuangenaro


also, I thought that dark matter is invisible, how can it be that it is visible in infra red suddenly?

It is not dark matter itself that is visible in infrared, but hydrogen atoms which are influenced by it.

Originally posted by Matthew Dark
Huh.
I'm curious...
if that area contains mass and has an intense gravitational pull that's strong enough to create a containment field of some kind of matter, then why isn't it dense enough to block the light from the stars behind it, or at the very least cause light passing through it to bend around it's gravitational field and render it somewhat visible?
Because, honestly, I'm no physicist, but all I see is a bunch of stars.
Perhaps I'm missing something?
Interesting stuff though.

Yes, dark (and ordinary) matter was observed to create this gravitational lens, distorting galaxies behind it.


But strong gravitational lenses like in the picture are rare. This dark galaxy has just one tenth the mass of our Milky way, so I am sure it is not massive\dense enough to create visible distortion.

reply to post by Matthew Dark


You don't really think space is a total vacuum, do you? Nah, way I figure it, the whole place has got to be packed full of atomic particles. All those atoms individually can't have much gravity, but putting them all together? I dunno, I'm not a physicist or astronomer.

The universe has got to be full of matter. It's just that all we can see are the stars and whatever their light reflects off of.

Originally posted by ModernAcademia
funny that you made this thread
I just made this today
www.abovetopsecret.com...

Perhaps there are no stars, but maybe there are Dark Stars!
Stars created by dark matter and therefore invisible!

So the question is.... is a star that is invisible till a star?

Maybe.. In the article it is written that Dark Stars should emit gamma radiation via neutralino anihilation, so if gamma rays are detected from VIRGOHI21, it could be them. Also, they should be linked with clouds of cold, molecular hydrogen gas, so that fits.

[edit on 28-12-2009 by Maslo]

consider.... perhaps the light havend reached us yet...we see only wat goes faster than the licht...

I think it would be helpful to include a brief explanation on what Dark Matter is, at the start of your post. Just to reflect basic questions further on into this thread, that could be answered by a simple google.com search.

Edited- To include a link to a brief summary on dark matter/dark energy from the people at NASA.

nasascience.nasa.gov...

[edit on 28-12-2009 by Paradox.]

reply to post by Maslo


You do realize that was in the news nearly five years ago, right? (read date on your link)
The real recent news is that they have yet discovered more evidence supporting the dark galaxy theory:

www.dailygalaxy.com...

New evidence has been discovered by an international team led by astronomers from the National Science Foundation’s Arecibo Observatory and from Cardiff University in the United Kingdom that VIRGOHI 21, a mysterious cloud of hydrogen in the Virgo Cluster 50 million light-years from the Earth, is a Dark Galaxy, emitting no starlight

[edit on 28-12-2009 by daniel_g]

reply to post by daniel_g


Uups.. yes, I read about the new evidence, googled something more about it and didnt noticed its so old.

Originally posted by donhuangenaro
I bet scientists are making wrong conclusions again... similar to ingenious conclusion about the cloud of dust Solar system is passing through 'that physics says should not exist.' link

also, I thought that dark matter is invisible, how can it be that it is visible in infra red suddenly?

As far as I know dark mater is a term used as a placeholder for the mass that seems to be out there but we can't see directly (only measure its gravitational effects. It is not necessarily some form of exotic mater (it may or may not be something special, all we know is that it does not emit light)

I don't think infrared has been quoted as the way they "see" the dark mater. I think they have spotted this galaxy by its gravitational pull.

-rrr