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Stars, galaxies and other stuff made of ordinary matter make up only a small percentage of everything that's in the universe. Based on detailed studies of galaxies and galaxy clusters, scientists say there's six times as much mass that we can't see directly. Instead, this mysterious dark matter is detected indirectly through its gravitational effect.
Now astronomers have put out a picture from the Hubble Space Telescope that reveals in detail where the dark matter lurks in a huge galaxy cluster known as Abell 1689.
The cluster, which is 2.2 billion light-years away in the constellation Virgo, serves as a gravitational lens for light coming toward us from even more distant galaxies. Like a funhouse mirror, the cluster's lens effect creates warps, magnifications and other distortions in the images of those galaxies. The Hubble team used software to analyze distortions in Hubble's view of 42 background galaxies -- and then reconstruct how much mass had to be concentrated where in order to create such distortions.
"The lensed images are like a big puzzle," Dan Coe of NASA's Jet Propulsion Laboratory said in an online statement. "Here we have figured out, for the first time, a way to arrange the mass of Abell 1689 such that it lenses all of these background galaxies to their observed positions."
The map of dark matter, superimposed on the visible-light view of the galaxy cluster, raises new puzzles. The findings confirm that Abell 1689's core has much more dark matter than scientists would have expected for a cluster its size. At some point in the evolution of the universe, scientists believe another mysterious factor known as dark energy began driving galaxies apart -- effectively stunting the growth of all galaxy clusters.
"Galaxy clusters, therefore, would had to have started forming billions of years earlier in order to build up to the numbers we see today," Coe said in a Hubble news release. "At earlier times, the universe was smaller and more densely packed with dark matter. Abell 1689 appears to have been well-fed at birth by the dense matter surrounding it in the early universe. The cluster has carried this bulk with it through its adult life to appear as we observe it today."
The research team's findings on Abell 1689 have just been published in The Astrophysical Journal, and more revelations about the interplay of dark matter and dark energy could be on the way: Coe said more conclusive results are expected from a project called CLASH (Cluster Lensing And Supernova survey with Hubble). During the CLASH survey, the space telescope will study 25 galaxy clusters for a total of one month over the next three years.
More about dark matter:
- Has dark matter's destruction been detected?
- Galaxies unlock new secrets of dark matter
- Gallery: Dark matter revealed
- The darkest mystery of them all
- Search for dark matter on msnbc.com
In addition to Coe, authors of "The Highest Resolution Mass Map of Galaxy Cluster Substructure to Date Without Assuming Light Traces Mass: LensPerfect Analysis of Abell 1689" include Narciso Benitez, Tom Broadhurst, Leonidas Moustakas and Holland Ford.
Connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.
Leave a Comment:
We have a few ideas on what dark matter is and no good ideas on what dark energy is. Until we solve these two unknowens we won't be able to speculate in any reasonable way about the universe. I think that the nature of dark matter and dark energy has been solved many times over, -- just not by us (mankind) Time streaches before us endlessly and we will solve this. It's a matter of time perhapes decades or eons. Great thinkers are still being born and eventually someone will put it all together. When we do that we'll be on the way to the stars.
The purported existence of something known as "dark energy" is only surmised as a means of explaining the supposed increase in the rate of expansion of the universe, which is deduced from measurements of brightness of distant galaxies and their redshifts.
Could it not possible that all of these assumptions are simply wrong, and that the universe is not actually increasing it's rate of expansion and hence no need for the suppostion of mysterious unknown "dark energies"?
Could it be possible instead that the observed variations in brightness are simply due to unaccounted for amounts of interstellar and intergalactic gas and space dust, which dim the observed light from the far off sources?
Hiya MikeyMike!
The observations that infer dark energy are not due to dust, gas, and other material. We are not measuring the dimming of the light - we are measuring the doppler shift of the spectrum.
Imagine that you are outside on a dark and foggy night. A large truck goes by, and you hear the change in tone as the sound waves are first compressed (as the truck approaches) and then stretched (as the truck recedes). If there is a great deal of fog and dust in the air between you and the approaching truck, the pitch would not bend up or down - it would be more muffled. Doppler.
It's the same with the redshift we are measuring for distant supernovae; their spectral lines are being stretched as they move away from us.
Cheers! ~Michael (AFM*Radio / Astronomy.FM)
Michael,
I know what the red shift is and what it means regarding speed and implied distance. Thank you for your condescending comparison to doppler effects with sound.
As I stated:
To clarify, the dimming would affect the perceived brightness of the observed galaxies and therefore their estimated masses, not necessarily their distances, although as I understand, the observed brightness is part of the calculation of distance, not exclusively the redshift. The point is, all this is based on certain assumptions, which if wrong, throw everything off.
MikeyMike, I'm sorry you found my answer condescending. It was an honest attempt to answer your question.
I apologize for wasting your time, and mine.
Don't worry Michael, MikeyMike is obviously in a league of his own.
OK Michael,
Sorry I took offense. I'm really just trying to raise what I think is a valid question. If I'm wrong, and completely off base, fine, tell me so, just spare me the high school physics lecture.
I simply don't understand why we need to postulate the existence of massive quantities of mysterious unknown stuff and give it names like "dark matter" and "dark energy". Didn't Einstein eventually admit that the supposition of a so-called "cosmological constant" was his biggest error?
Could there not be a simpler explanation? I.E. Unaccounted for interstellar dust and rocks (or gas or other basically "regular" matter).
Does not the principle of Occam's razor apply? If we are forced to invent mysterious invisible and unknown stuff in order to explain our observations, should that not be a giant sign that there's something wrong with the calibration of our instruments?
Mikey : What you are missing is that the observation tells us is that objects are being gravitationally bound by something that cannot be seen, hence, the word "dark". If it was dust or any other normal matter, it will give off electromagnetic energy : light, infrared, radio, ultraviolet, xrays and gamma rays. The thing is, with the ability to "see" in all of these wavelengths, they cannot "see" anything. So whatever is out there, it doesn't give off electromagnetic energy, doesn't interact with normal matter ( can pass right through) and our only indication of it's existence is through gravity. Sometimes there are things that are just that complex and no amount of simplification can happen.
TReed,
I must indeed be missing something. How would low density space dust emit radiation? If it's as cold as the space it's floating in there's little infrared. There's no visible light. and forget x-rays and gamma rays, those are only going to come from highly heated or charged or gravitationally influenced sources.
Correct me if I'm wrong, but I thought I thought only stars and such would emit the types of radiation we're talking about. Sure there's quasars and rotating black holes and exotic things like that, but those aren't the issue.
Someone above mentioned brown dwarfs, which makes some sense in terms of what I'm trying so unsuccessfully to argue, because they are, if I understand correctly, failed stars which are too low in mass to ignite the fusion reaction which would cause them to emit the quantities of radiation which we would then detect at a distance, hence they are a possible candidate for the sort of thing I'm talking about, which I acknowleged, up above.
Talking in terms of seeing things, we can't even "see" the planets which orbit relatively nearby stars (with as I understand it one recent exception which has been visually imaged as a tiny 4 pixel smudge). We detect these planets by the gravitational effect and/or decreased luminosity during transit of the stars they orbit.
So if we can't "see" planets around other stars, how would we see asteroids, or their equivalent, if they existed around other stars? We can't see most of the stuff in our own Kuiper belt and in the Oort cloud, can we? Is there something I'm missing here? Can we indeed detect cold rocky icey objects in the depths of space by some means of which I'm unaware? If so, how?
And if our outer solar system is pretty packed with this type of stuff, relatively speaking (I keep saying at "low density"), then wouldn't most other stars be as well? And galaxies, on the larger sense?
Are there not huge clouds of dense dust imaged in famous photos such as the Horsehead nebula and the "Pillars of creation"? And if there is enough dust in some places and there happen to be radiant sources illuminating it in the right ways to get these types of famous pictures, then could there not be massive quantities of much more dispersed dust spread out virtually everywhere? Maybe enough to produce gravitational effects on a galactic scale?
One more question, and then I'll shut up. You mentioned:
What would do that? Neutrinos, right? These almost impossible to detect tiny little bastards that can pass right through the entire earth until they hit just the right molecule of water inside a bazillion gallon tank buried somewhere under Japan and reveal themselves in a flash of light? Yeah, I've heard of neutrinos. I'll admit that I don't understand them completely, but if you're trying to convince me that virtually massless particles could make up most of the mass of the universe, I'm sorry, but that's just nonsense.
I have thought about that as well. While dark matter has been compared to as the left over portion of the universe in which baryonic matter resides, it actually accounts for 99% of the universe. Dark matter exists (or does not exist) as massless quantum containments, better represented via the SuperString Theory. Its measure would be an absence of mass density, or degrees of negative density. It infiltrates all empty space, even the empty space within baryonic matter itself. It would appear that baryonic matter is the anomaly, and dark matter is the normal condition of our SpaceTime continuum. It is the intrusions of baryonic matter within the universe that cause displacement and warping in the SpaceTime fabric of the non-baryonic matter in which it resides; And perhaps it is even qualifying the gravitational force which is traditionally attributed to baryonic matter. But enough said, I wouldn't want to give away to much of my research before publishing.
Well said, I like this, it took me a few reads to get it.
Cool link...concerning such ponderances....
http://www.becomereal.com/quantum_relativity.htm
In the begining, space was without gravity. In the end space will be without gravity. Hard to believe that all this is all temporary. When our universe becomes a black hole and matter turns back into space, space without gravity. It is hard to imagine absolution of gravity. Gravity is what keeps thing around and the absense of Gravity lets us float away. The two are reason we have a solar system
Only 2.2 billion light years away? Geez, all I need to figure out is how to travel 2.2 billion times faster than light and be there instantly? Hmmmm, maybe or have gone backwards in time forever.
Just had another thought that galaxy cluster Abell 1689 may even be non existent by then, oops!
Actually, you would be there in one year.
great reply
On the off topic of dark energy, which always arises when talking about dark matter, there is one thing I do not understand: Red shift can be caused as light escapes a gravitional field. How can scientists accurately measure and attribute red shift to universal expansion versus the initial escape of a gravity well and the long term effects of gravity as light travels great distances? Do they account for this, and if so, how?
While the concept of gravitational redshift demonstrates a real responsive to gravitational differences, the expectation that detectable light wave/particle would remained as a longer wavelength in free space is questionable. There is no viable research that would suggest that the affected light retains its previously beleagered state; the speed of light is constant (and probably more so relative to the dark energy of our SpaceTime continuum).
Rather the expected detectable redshift is an expected measure of our motion from the object being observed. So it would have to be the gravity well of our immediate environment (i.e. plant, solar system, or galaxy) that might be responsible for this effect being observed by us. Therefore the doppler theory still makes more sense to me.
Mikey : All normal matter vibrates, unless it's at absolute zero. The coldest temperature in space is 3 degrees Kelvin, that's 3 degrees above absolute zero. Even at that temperature there is electromagnetic radiation that can be detected as long as there is enough density to be "seen" by the different telescopes. In this case, infrared and radio telescopes.
The other objects that you talked about: brown dwarfs, planets, asteroids, comets and dust, are just to small, even if they were all grouped together to be seen by visible telescopes. The dark matter objects that the article is talking about are huge. A dark matter halo around a galaxy is about twice the size of the galaxy. The cluster in the article is over 2 million light years wide for the gravitational lensing, which is where the dark matter object resides. As a point of reference, the Milky Way is just 100,000 light years across.
Now, you did make reference to neutrinos. There are three types and one has mass. Is there enough neutrinos with mass to cause the gravitational effects? That hasn't been answered yet. Neutrinos are included in the nonbaryonic particles and it is these types of particles that is believed to be dark matter. Here is a link that might help, http://atropos.as.arizona.edu/aiz/teaching/nats102/lecture23.html .