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Dark Matter Discovered 386
sebFlyte writes "Wired is reporting that scientists have come up to a solution as to where all the matter in the universe actually is. Experiments being done with Chandra, NASA's X-ray telescope have shown up a likely candidate for the solution of the dark matter problem. There are massive quantities of Baryons in a super-heated gas cloud several hundred million light years away."
Fascinating (Score:5, Funny)
There are massive quantities of Baryons in a super-heated gas gloud several hundred million light years away."
Which, IMHO, is a damn fine place for them to be, rather than here.
The absorption pattern, as detected by Chandra, is consistent with interference caused by carbon, neon, nitrogen and oxygen ions -- in other words, baryons.
It's really a neon sign on Frogstar World B announcing the construction of a restaurant to be constructed on this location in several billion years and reservations are welcome.
"Assuming that what we see is a standard portion of the universe, we extrapolated the data and derived the volume density (of baryons in all the clouds) -- and it's consistent with 50 percent," said astronomer Fabrizio Nicastro, of the Harvard-Smithsonian Center for Astrophysics and lead author of the study.
Later a two-headed, three-armed man entered and ate a piece of fairycake and destroyed their model.
Whereas baryons account for 4 percent of the total matter and energy in the universe, dark matter is thought to make up 23 percent. The remaining 73 percent of the so-called matter-energy budget consists of what scientists call "dark energy." This energy acts like an anti-gravitational force that, in theory, is causing the universe to expand rather than contract.
And here I thought it all existed somewhere along Lucas Valley Road and explained the Jar Jar character and Episodes I-III...
I knew theyd eventually find it (Score:2, Funny)
Wait a sec, this story isn't about "dark matter" (Score:5, Insightful)
In other words, if regular stuff is about 5% of the energy density of the universe, with dark matter at about 20%, and dark energy at about 75% -- the stuff in this story comes into that 5%, ie, regular stuff and not dark matter.
Re:Wait a sec, this story isn't about "dark matter (Score:3, Interesting)
Which is what they're constantly doing. I heard the theories in my astronomy class. There's plenty of them, such as brown dwarves just drifting around out there. How do you explain them? Well some star has a vector or some light appears bent (lens effect) and it's figured there's some large enough object out there not emitting light which is doing it. And who's to say i
Re:Wait a sec, this story isn't about "dark matter (Score:5, Insightful)
Math is a very useful tool in astrophysics, but there's a reason that math is a separate department from any physical science.
Re:Wait a sec, this story isn't about "dark matter (Score:5, Informative)
Re:Wait a sec, this story isn't about "dark matter (Score:2, Interesting)
Re:Wait a sec, this story isn't about "dark matter (Score:3, Informative)
It seems perfectly reasonable that there exists matter that's not formed into glowing plasma balls and is thus harder to spot.
But that presentation is kind of prosaic, and wouldn't sell lots of issues
Re:Wait a sec, this story isn't about "dark matter (Score:5, Informative)
Dark matter might yet prove to be baryonic, but since about 70% of the universe is the even weirder dark energy, why is it so impossible to believe that 25% could be a new type of matter that interacts gravitationally, but not in other expected ways?
Re:Wait a sec, this story isn't about "dark matter (Score:5, Interesting)
The story is a bit about dark matter, because there is a dark matter presence implied by the newly discovered gas clouds. But that's no surprise - the observed structure of ordinary galaxies already implies that they as well are permeated with dark matter.
Re:Wait a sec, this story isn't about "dark matter (Score:5, Interesting)
There sure is dark matter out there that we don't understand well at all, and probably more than one kind. Neutrinos are one form, since recent experiments indicate they do have some mass. Neutrinos are pretty exotic compared to normal baryonic matter. There may well be weirder stuff.
Agree with you though, that Star Trek overdoes it.
Re:Wait a sec, this story isn't about "dark matter (Score:4, Informative)
The page can be found here. [uchicago.edu]
So they say they've found the missing matter... (Score:4, Funny)
Re:So they say they've found the missing matter... (Score:3, Funny)
As my friend Paul Z. said, "Socks are the larval form of hangers."
Re:So they say they've found the missing matter... (Score:2)
And your solution for uneven fading of the socks after multiple washes is.......?
I buy multiple socks at the same time. I still end up trying to figure out what is the optimum set of matches (many partial shade matches, without too many gross shade mismatches)
Re:So they say they've found the missing matter... (Score:3, Funny)
Buy white socks.
Re:Fascinating (Score:2)
And maybe the north shore accent
*runs from menacing Oxford shirts...
Great... (Score:2)
Glouds (Score:2, Funny)
Re:Glouds (Score:2, Funny)
This is astrophysics, folks (Score:3, Funny)
Re:Fascinating (Score:4, Funny)
It's really a neon sign on Frogstar World B announcing the construction of a restaurant to be constructed on this location in several billion years and reservations are welcome.
Such a sign would not make any sense.
Obviously the restaurant willon forewhen constructed already.
Re:Fascinating (Score:5, Funny)
The metalingual speaker is conceptually at the forewhen temporal point. His subjunctive "now" is forewhen. In this referrence frame the restaurant clearly will be a retrospective actuality (willan), rather than will be a prospective actualization (willon).
The fact that you needed end the sentence with an the explicit temporal adverb 'already' is a huge tipoff, an awkward construction to bend a prospective tense onto a retrospective object. Changing the tense to willan forwhen makes that explicit temporal adverb clearly redundant. Fixing the tense and dropping the explicit temporal adverb leave the much cleaner sentence:
Obviously the restaurant willan forewhen constructed.
-
Re:Fascinating (Score:3, Funny)
Holy shit.
A grammar nazi for an entirely made up set of grammar, meant to cover a situation that can't exist, presented in fictional comedy novels.
That's AWESOME!!
Doug
Nibbler? (Score:5, Funny)
Nope... (Score:2, Funny)
Baryons (Score:4, Informative)
http://en.wikipedia.org/wiki/Baryon [wikipedia.org]
Re:Baryons (Score:2)
Re:Baryons (Score:5, Informative)
http://www.slashdot.org/ [slashdot.org]
Can I have my +5 informative now??
Re:Baryons (Score:3, Funny)
http://www.answers.com/informative&r=67
I got nuthin.
Re:Baryons (Score:2)
Re:Baryons (Score:5, Funny)
Yup, noticed that. Though I think what you wanted to say was, "In case anybody's wondering what a hyperlink [answers.com] is..."
In case.... (Score:5, Funny)
> > http://en.wikipedia.org/wiki/Baryon [wikipedia.org]
> In case anyone's wondering what slashdot is...
> http://www.slashdot.org/ [slashdot.org]
In [wikipedia.org] case [answers.com] anyone [reference.com]'s [merriam-webster.com] wondering [google.com] why [wikipedia.org] the [answers.com] hell [reference.com] am [merriam-webster.com] I [google.com] wasting [wikipedia.org] my [answers.com] time [reference.com] so [merriam-webster.com] pointlessly [google.com].... I [wikipedia.org] have [answers.com] no [reference.com] life [merriam-webster.com].
Re:Baryons (Score:2, Insightful)
1) Particle physics
2) Nucleons, Hyperons, Fermions
3) The strong nuclear force
4) Fermi-Dirac Statistics
5) The Pauli Exclusion Principle
6) Hadrons, Quarks, and Pions
Re:Baryons (Score:3, Funny)
Re:Baryons (Score:3, Insightful)
Hmm (Score:4, Funny)
Re:Hmm (Score:2)
Picture (Score:5, Funny)
Re:Picture (Score:2)
Re:Picture (Score:5, Funny)
Ummm (Score:5, Informative)
Re:Ummm (Score:4, Insightful)
If it turns out that it is normal matter after all, and we just had trouble seeing it, we have still "discovered dark matter."
Another way of putting it would be, who killed the prime minister of Georgia? If it turns out later that it was an accident from a faulty space heater, did we find out who killed him? Just becuase we were expecting a who and got a what doesn't mean the question wasn't answered.
Re:Ummm (Score:2)
For this to explain dark matter, the clouds they discovered would have to be less than ONE TENTH of the averag
Re:Ummm (Score:2)
Re:Ummm (Score:3, Informative)
Wired Magazine seems to be getting their terms confused:
But one candidate for the "dark matter" (everything we can't see) *is* "baryons" -- which is ju
Re:Ummm (Score:5, Informative)
Dark matter is the extra mass needed to explain the observed motion of astronomical bodies in terms of known forces (ie gravity) after all the known matter is accounted for. In particular, galaxies rotate like rigid bodies (the same angular velocity at all radii) whereas the distribution of known mass (eg stars) suggests they shouldn't. An enormous amount of extra mass must be within the galaxies in a specific distribution to make this happen. (The alternative, which astrophysicists dislike, is that our equations for gravity are wrong for large distances.) This cloud is outside of a galaxy, so it isn't the missing matter.
Now, there may be other discrepancies between what we can see and what we can compute should be there, and this cloud could explain some of those.
Wired (perhaps) isn't confused. You (perhaps) are. (Score:5, Informative)
Distinguishing between baryonic matter -- stuff that bears any resemblance to everything around you, whether it is visible or not -- and other "dark" matter that does not fall into that category, is actually pretty commonplace in astrophysics. This seems like semantics, but turns out to be an important distinction.
The point is that the fraction of baryonic matter in the universe is, we think, reasonably well constrained (by both observations of light element abundances in conjunction with Big Bang nucleosynthesis models, and by measurements of fluctuations in the cosmic microwave background) to be only about 5% of the total mass/energy density. Yet there's an additional matter component (accounting for about 25% of the total density) that we know little about -- this is what most astronomers mean when they say "dark matter" these days.
This article says nothing at all about that 25%. It does, however, provide some clues towards a more complete accounting of the 5% that is "normal" (i.e. baryonic) matter. This is a very significant result, but the slashdot writeup and most of the comments to this article are completely distorting it.
The puzzle regarding the "normal" 5% was this: in the local universe (redshifts less than 2), only 10% or so of it is luminous matter, stars and galaxies and the like. More (40% or so) has been accounted for by studies of cool clouds of gas residing between stars, but this still left 50% in an unknown reservoir of baryons. Theory/simulation had suggested that one such reservoir might be the "warm/hot intergalactic medium" -- gas that is heated to millions of K.
The problem is that detecting low-density gas at that temperature is quite difficult, partly since most bound electrons have been lost. Only the more massive elements retain any electrons, and so can be visible in absorption in the FUV or X-rays.
What the paper discussed here (published today in Nature) does is to describe a plausible-looking detection of such filaments of "warm-hot" gas, through X-ray absorption. They use this detection to extrapolate a matter density of this WHIM component, and find that it could account for 30-50% of the baryonic mass, and so constitute the "missing" baryonic matter.
Note that this says nothing at all new about the 25% of truly "dark" non-baryonic matter.
One fairly large quibble is that the 30-50% number represents an extrapolation from just two absorbers, over a comparatively short distance, to infer the WHIM density in the whole universe. That's sort of a big jump, in case that part wasn't obvious. But you can't do this sort of analysis for very many sightlines -- you need a really bright emitting object on the other side of the WHIM clouds if you're going to see them, and such objects are few and far between -- so for right now that's what you get.
If you happen to be somewhere that has a subscription to Nature (most universities do), you can check out the two articles related to this in today's edition:
There's a "news and views" article [nature.com] by Mike Shull that's a nice summary of the issues involved. And there's the full research article [nature.com] by Nicastro et al.
Hope that clears at least a few things up. If I have time later tonight, I'll try to come back and respond to some of your other points.
cheers.
Re:Ummm (Score:5, Informative)
Dark matter isn't mysterious or unordinary. Dark matter is usually extremely cold but otherwise ordinary matter. Because it's so cold, it can't emit light, hence "dark" matter. So, while they did discover dark matter in the sense that most astrophysicists use the term, they did not discover the really weird stuff.
You have, however, picked up on an important distinction. They found dark matter, but what they really need to find is dark energy. Dark energy is thought to comprise something like 70% of the energy of the universe, and yet, even today, it is a complete mystery.
I dunno whether you're confused about this stuff, but your post makes some statements which are at least confusing, and possibly wrong, depending on what you meant (I can't really tell). So to clarify, for anyone who cares: the energy content of the Universe appears to have three components:
Re:Ummm (Score:4, Interesting)
What I was trying to point out, but evidently with little success, was that the article was hyping the discovery. It is certainly important (as you might gather from the fact that it is being published in Nature). The article, however, summarizes the physicists' findings but allows the reader to think that the "dark matter" that the article refers to is that really mysterious stuff that science fiction writers like to write about, not the less mysterious stuff that the physicists were actually talking about.
And, by the way, dark energy (which indeed is horribly named) is a huge mystery. Ask a particle physicist to calculate the vacuum energy density and he will give you an answer that is incorrect by many, many, MANY orders of magnitude. See http://www.site.uottawa.ca:4321/astronomy/index.h
Re:Ummm (Score:4, Interesting)
While we have some ideas about the non-baryonic dark matter that might pan out soon, indeed, we're clueless about the dark energy in a very profound way.
Are you thinking what I'm thinking? (Score:2)
Re:Are you thinking what I'm thinking? (Score:2)
no no no NO! (Score:2)
PERFECT VACUUM!
e
Must resist.... (Score:2)
Those giant gas clouds got a Baryon enima?
Gloud (Score:3, Funny)
Google wants to know if you mean "gas cloud".
Re:Gloud (Score:2)
If WIRED says it, it must be true! (Score:5, Funny)
WIRED also said that "Push is the next Big Thing."
Re:If WIRED says it, it must be true! (Score:3, Informative)
Wrong Name (Score:4, Insightful)
Re:Wrong Name (Score:2)
Re:Wrong Name (Score:4, Interesting)
Re:Wrong Name (Score:5, Interesting)
YOu gotta admit, though... There really isn't a good explanation of why gravity SHOULDN'T change over vast distances.
F=ma = G*M*m/(r^2) -- 'G' is derived observationally. Only a few hundred years of observation tell us that it is a constant. Only a few dozen of those actually FROM SPACE -- Perhaps a few hundred years more will show that it is proportional to some (presumambly negative) exponent of 'r' (distance). Perhaps not.
I admit to preferring MOND over imaginary matter. However, what I like the most is that the guys have open minds... unlike the typical 'scientist' favoring NB matter -- a bad hypothesis usually treated as sound theory. If NB matter were treated with the caution that MOND is, I would enjoy reading about it. Instead most authors treat it as assumed fact and build upon it. Bah. Excel can curve fit data; doesn't mean I assume a random scatter plot can be modeled by a 4th order equation.
Not quite... (Score:5, Informative)
Read more at the press release from the Chandra team at Marshall: http://www.spaceref.com/news/viewpr.html?pid=1604
Dark matter is yet another topic altogether, as is the even more elusive dark energy.
More Information (Score:4, Informative)
They are extremely interesting for anyone fascinated with physics.
I thought that solution had passed away (Score:2)
WRONG TITLE, Sigh...... (Score:5, Insightful)
They HAVE NOT found dark matter, they've found the 'missing matter' as the article says. They have found a clue as to the dark matter, as a result of the discovery.
Although discovering the dark matter would be much cooler, (yeah I was excited when I read the title).
[rant] Why is it the only 3 times I've 'emailed the on duty editor' before publishing, I've been ignored and the mistakes gone through?? [/rant]
but I thought... (Score:2)
but then again, some crazy girl with a bird hit me over the head with a rock, so I'm not thinking very clearly...
Re:WRONG TITLE, Sigh...... (Score:4, Informative)
Dark matter was originally used to refer to matter that was not yet accounted for. Non-baryonic matter being a subset of Dark Matter.
The issue has been beaten to death so badly by poor authors that 'Dark Matter' is becoming assumed to refer to NB matter.
It is hard to argue that you are wrong, but equally hard to win an argument saying you are correct.
But now where... (Score:2, Funny)
I mean really now, Baryons, oh come on nasa. Try something new and exciting like, antiquantafusitrons.
It beats (Score:2)
Cleared up nicely... (Score:4, Funny)
Wikipedia cleared that one up nicely!
Difference between Baryons and Dark Matter (Score:2)
But, what I'd like to know... (Score:2, Insightful)
Is how do these extremely difficult scientific questions get answered so quickly lately.
It was just a couple days ago that slashdot reported that dark matter was being postulated as the reason for the extra mass of galaxies:
Simulating the Universe with a zBox [slashdot.org].
Now, in less than a week, we have proof for the existence of dark matter? Amazing!
How can scientists go from hypothesis to proof in such a short time? Are we really progressing by such leaps and bounds? Or, is this an example of media ju
Re:But, what I'd like to know... (Score:3, Insightful)
Dark matter question (Score:2)
Re:Dark matter question (Score:2)
Re:Dark matter question (Score:4, Informative)
Not correct, there are two classes of elementry particles (that we know about) Bosons [wikipedia.org] and Fermions [wikipedia.org].
Bosons are things like :
Fermions are things like :
IANAP, but two photons cannot cancel each other out, however two beams can (assuming they are co-axial and anti-phased).
As for the flashlight, general light is not regular so you certainly can't make one using interference.
That's strange.... (Score:3, Funny)
Dark matter (Score:2)
How they found it (Score:5, Funny)
Google? (Score:3, Funny)
But what about galactic cohesion? (Score:2, Interesting)
These clouds are great for a macro-framework missing mass solution but unless they are found to exist in a somewhat smooth (or central) distribution in a galaxy how would massive clouds several
Re:But what about galactic cohesion? (Score:3, Interesting)
Galaxy rotation velocity curve Java applet explains this problem. [queensu.ca]
Assuming... (Score:5, Funny)
An astrophysicist, a physicist, and a mathematician are attending a conference in Scotland. During a break, they take a walk through some of the countryside, and come upon a black sheep.
"Aha," exclaims the astrophysicist. "I had no idea that all sheep in Scotland are black."
The physicist looks at her colleague in disbelief. "All sheep in Scotland are black? Are you nuts? We've only seen one sheep!"
The mathematician interrupts. "And only one side of that sheep."
Who knew... (Score:5, Funny)
Duh... (Score:3, Funny)
Baryons are *NOT* dark matter (Score:2)
In other words, baryons in those clouds are the *EVIDENCE* of dark matter, but not the dark matter itself.
Wrong wrong wrong! Aarrrgh (Score:2, Informative)
At least there were... (Score:5, Insightful)
At least there were, several hundred million years ago.
Exclusive Photos (Score:3, Funny)
Pretty fascinating if you ask me.
You all missed the Google ad (Score:3, Funny)
I just wonder if they throw in free shipping.
Good work but the headline is overheated (Score:5, Insightful)
The current work is an improvement over previous studies, and is good work. But the headline rather sucks. I thought we'd detected axions or something, even though I'd already read about this result.
I teach techniques to estimate cluster masses based on X-ray emission, and have used the Chandra X-ray Observatory myself. A headline about such work shouldn't trick me.
Rethinking Newton on Large Scales... (Score:3, Interesting)
ZERO is what MOND [MOdified Newtonian Dynamics] predicts because if the compact nature of the galaxy in question, it is still in the Newtonian regime.
It's time to reconsider Newton on large scales.
Re:Aren't baryons just normal matter? (Score:5, Informative)
But baryons are by no means the counterpart to tachyons. All known elementary particles in the universe are either fermions (particles with spin in integer multiples of 1/2) or bosons (particles with integer spin). Bosons include the photon, the gluon and many others. The fermions are further subdivided into leptons and quarks. Leptons include the electron and the electron neutrino among others. Baryons are particles made up of three quarks, and are fermions and include among others, the proton and neutron, which are the most commonly found baryons in nature, since all heavier baryons normally decay.
Two quarks (fermions) can combine to form mesons, which are in fact bosonic in nature (since two quarks with spin half combine to form a particle with integer spin).
Hope that confused the issue a little
A bit more on-topic: Finding baryons in this amount is a big deal, since baryon has previously been suspected to primarily exist in galaxies, and only in small amounts outside galaxies. While it by no means doesn't solve all problems of cosmology, it is a big help.
Re:Aren't baryons just normal matter? (Score:2)
Am I thinking of a different term, or aren't "baryons" just the counterpart to "tachyons?"
You're thinking of "bradyons". Tacyons travel faster than light. Photons travel at light speed. While bradyons travel slower than light. Baryons are bradyons along with all other matter we've seen so far.
Re:Aren't baryons just normal matter? (Score:5, Interesting)
First, I had to look up "tachyon". You are right, tachyons are apparently particles that travel faster than the speed of light. I've only heard the term from Star Trek, and for the time being that's where these particles are from - the realm of (science) fiction. I've certainly never had them mentioned in class!
Baryons are not the counterpart to tachyons. Baryons are simply particles that are made up of quarks. The two best known examples are neutrons and protons, which make up virtually all of the stuff you own. Yes, baryonic matter is pretty much everything we interact with.
Two examples of particles that are very common and all around us are electrons and neutrinos. You're familiar with electrons (which are not baryons!), and the nuclear reactions in the Sun are constantly producing a mind-boggling number of neutrinos. Generated in the centre, they travel at nearly the speed of light which means that the ones passing through your body right now are about 8 minutes old. By comparison, the light from the Sun (photons, also not baryons) bounces off all the photons there, so by the time it actually reaches you it's about a million years old.
Finally, and most importantly, dark matter has not been discovered. You are also right in that the reporter is very much out of his depth. The article states that there is evidence for baryons to be found in places where we have not seen them before. What's one theory as to how they got there? Dark matter.
Re:Dark Matter found? (Score:2)
Puzzling? You should hang out with more females. They're just talking about someone who's still sitting at the table. They usually know what each other is thinking about a person so when one says "I'm going to the bathroom" it's like announcing "If you're thinking what I'm thinking, come with me to discuss it." When the other says "Ok I'll come with you" they're acknowledging that th
The counterargument (Score:3, Interesting)
Clearly not all matter is in stars, so if that is your definition, then some dark matter must exist
Re:Maybe its a big fudge (Score:4, Interesting)
2. Several ways --- rotation, motion of a number of satellite galaxies, mass/light ratio, Tully-Fisher relation, and, if it's a spiral, simply by the size if we know the distance (this is pretty rough, but a decent indicator)
3. Within a galaxy, I don't think so. But intra-galactic dark matter is just one type. There is also non-luminous matter in between galaxies in clusters to account for their motion. Hot X-ray gas is one candidate, but I thought I remembered that there didn't seem to be enough of that stuff to account for cluster dynamics. Maybe this new stuff will help out, though the mass deficit was much more than this 2% if I recall correctly, and is probably non-baryonic.
3. Yes, they should. That's the problem. Outer stars and globular clusters are orbiting way to fast if all the mass in the galaxy is traced by luminous matter. A good model to account for the rotational behavior is a spherical halo (not just a disk) of non-luminous matter. This is the intra-galactic dark matter, and not relevant to the article.