Ring Of Stars Found Around Milky Way

LoPingHo writes "Scientists have found a ring of stars around our galaxy that has previously been undetected due to the faintness of the stars. The article says that it only amounts to 1% of the galaxies mass, but if they are just now finding those, that means there could be even fainter ones there too. Could this be part of the elusive 'dark matter' talked about so much lately?"

Comments

Thanks!

[geekoid]

I was wondering where I put those.

Dark Matter?

[ancukiewiczd]

I always thought that dark matter was perfectly invisible, and not just a large number of very dim stars. Maybe those stars could help account for the missing mass, but measuring at 1% it doesn't seem very likely.

Re:Dark Matter?

[spanky1]

I think it is called dark matter because there should be more matter in our galaxy than is currently visible/detectable. But finding more visible matter would seem to reduce the need for as much "dark" matter.

Re:Dark Matter?

[pyrrho]

Dark matter must either be some strange particle, or must be a change in the laws of gravatation (the latter is considered not likely).

Cool baryonic matter not emitting much light has been eliminated from the possibility of accounting for all the "missing mass". A more promising idea is something non-baryonic but massive, like a massive neutrino. Well, more actually than just one of those.

For more information try google "non-baryonic dark.matter" or "baryonic dark.matter".

It's amazing really, astronomy is still at the forefront of physics here on earth, when they figure out what dark matter is and can reproduce that here on earth, it's likely to be one of the biggest things in physics (for a while).

Re:Dark Matter?

[mao che minh]

Dark matter is just the term for matter that we can't detect. It can be baryonic material or even black holes. "Dark" doesn't mean 'invisible' when they use it in that context.

Re:Dark Matter?

[pointym5]

I thought it couldn't be baryonic matter under most good-candidate expansion theories.

Re:Dark Matter?

[prizzznecious]

Cool baryonic matter not emitting much light has been eliminated from the possibility of accounting for all the "missing mass".

Could you provide some sort of support for that claim?

There are two realms of explanation for the supposed enigma of Dark Matter. One is that matter like these stars have simply escaped our detection; in short, that it is our instruments that are at fault. The other is that our instruments have reached perfection (at detecting the things we can explain), and we've looked everywhere, and, well, supermassive and invisible objects exist all over the place.

The latter is a pretty theory, appealing to the imagination and to the egos of scientists. It's also completely ludicrous as the sole explanation for observed mass/gravity discrepancies. A few years ago, scientists barely thought brown dwarf stars existed. Now we know that they're everywhere, and in all likelihood far more prevalent than scientists currently have the capacity to investigate. What else are they missing?

These things are hard to see across the vastness of space, especially when they emit little or not light. That doesn't mean they aren't there. As .. improbable (coughhackcough) as it might seem to some, it's far more likely that our instruments just aren't strong enough. That's all.

Re:Dark Matter?

[reverseengineer]

Dark matter doesn't necessarily need to be completely invisible, just rather hard to detect. Its exact properties depend on the sort of dark matter candidate you are considering. The two general types of dark matter candidates are MACHOs- MAssive Compact Halo Objects, which are relatively large (but very small on a galactic scale), dim objects such as gas giant planets, brown dwarfs, and black holes. Many of these object emit faint radiation, but are completely washed out by brighter objects nearby, or are merely too dim and too far away. The major method for searching for MACHOs is gravitational microlensing- if a MACHO passes between us and a faraway star, its gravity should bend the star's light like a lens, making it appear temporarily brighter, with the intensity chance and duration being indicative of the mass and velocity of the MACHO. The other major candidate is that an invisible cloud of massive particles surrounds our galaxy. These particles would have to have a gravitational field (i.e., nonzero mass), but must be extremely nonreactive- dark matter seems to have effects on a galactic scale, but seems to be undetectable or nearly undetectable on earth. Some physicists think that no known particle meets this description, and are looking for WIMPs (Weakly Interacting Massive Particles) I believe these were named before the MACHOs, btw. As their name implies, they interact with normal matter very weakly- they can pass though many miles of solid matter (like the entire earth) and emerge unscathed. Detection efforts usually involve sensitive experiments carried out deep underground. There are other physicists who believe the dark matter has been located already- in the humble neutrino. Results from the Super Kamiokande neutrino detector strongly suggests that the neutrino, long believed to be massless, has a very small but finite mass. The exact mass is unknown, but should exist because neutrinos oscillate freely among its 3 varieties (electron, muon, and tau), which could only occur if the neutrino had a mass. This mass is very, very small- much smaller than that of an electron, even, but there are so many neutrinos that even a tiny mass would mean that neutrinos make up the vast majority of matter in the universe.

Re:Dark Matter?

[pyrrho]

first off, to not pose: I'm a software engineer, not an Astronomer, though my statement of what was "considered less likely" is based on what I've been recently told by astonomers I work with.

This was an interesting read, though as I said, it was found just through a google search.

I admit it's all speculation and half of it I don't claim to actually understand to the level of making a good argument.

But think of a couple things. One, it's not about perfect instruments, it's about instruments that are good enough to see what you are looking for. If I have ten marbles in a dish, but it weighs as much as twenty... I know I should see the extra marbles if they are ordinary marbles. We are not talking about a little bit of missing mass, we are talking about a huge bit of missing mass.

Another, it's about what you do see. For example, there cannot be a diffuse gas in the galaxies to cause this effect because (a) it would not have enough mass and (b) you could see absorption lines of the gas.

It's not like we are looking for something small, remember... we're looking for something big! Something with a lot of mass that for some reason doesn't or can't glow.

And of course I agree that relatively exotic dark matter cannot be the only source of dark matter, some is just undetected baryonic matter. The rub is that it doesn't seem there could be enough of that to account for all the dark matter, a significan portion looks to be something exotic or at least non-baryonic.

Re:Dark Matter?

[CraigParticle]

Could you provide some sort of support for that claim?

Aside: Really, it's not about the egos of scientists, or the perfection of our telescopes and instruments. Goodness knows, if they were so perfect, we wouldn't be begging for money to build new and better ones! :)

The link that pyrrho mentioned describes the basic reasons why baryons can't be all of the hypothesized dark matter. And since 1996 (when the article was written), the evidence has become vastly more convincing. I'll attempt to summarize.

Sure, we could hypothesize that the Universe is filled with "dim, normal stuff" like brown dwarfs, white dwarfs, lost airline luggage, missing socks, dryer lint... but we're just not able to see them. Fair enough. But there is a limit to this argument for numerous reasons.

• There are not enough baryons in the Universe. The Big Bang only made so many baryons, and this is something we can measure. The limits on the number of baryons in the Universe are quite tight -- only, say, 5% of the mass needed to give the Universe an uncurved geometry.

  Okay, so maybe we just live in an empty, open Universe! But numerous measurements of the curvature of the Universe, in particular recent observations of the cosmic microwave background itself suggest that the curvature is not open but uncurved. So we live in a Universe with plenty of gravitational matter of some form or another. Aside: we are gathering a huge amount of information by looking at the angular sizes of the bumps and dips in the cosmic microwave background, which is fossil radiation from the Big Bang and a few percent of the static you see on your TV when tuned to a blank UHF channel. This page shows what the CMB power spectra (that is, how many inhomogeneities occur at a given angular size) look like, and how changing various cosmological parameters has an effect on the spectrum you'd expect to see. Try out changing the baryon density -- the effect is quite pronounced. It also says that the Universe has the number of baryons that Big Bang theory says it should have.

• Even if we can't see brown dwarfs (or basketballs, for that matter) by their reflected light, we CAN infer their existence by their gravitational interactions with light, i.e. gravitational (micro)lensing. It's not that we "haven't looked hard enough" -- but rather that "if the Universe was full of brown dwarfs, there'd be tons of observable microlensing events". But microlensing events are exceedingly rare. In this case, the null result is interesting, because it highlights that baryonic matter is not as prolific as we want/need!

So this makes us all feel a bit uncomfortable, because either some of the fundamental tenets of cosmology are flawed (even though they explain nearly all of the observable Universe, right down to the abundances of the elements and the large scale structure of galaxies and the cosmic microwave background, the recession of galaxies etc.) ... OR ... the Universe is mostly filled with matter what is unlike anything we yet know how to explain.

It's going to be a fun ride! :)

Re:Dark Matter?

[Alsee]

Dark matter is just the term for matter that we can't detect. It can be baryonic material or even black holes. "Dark" doesn't mean 'invisible' when they use it in that context.

Nope. When the dark matter problem was first discovered they thought (hoped) that it was just normal matter that we can't see. It isn't. This post provides a pretty good explanation.

Note: that post only lists a few of the reasons. There are several others. Either we've made a whopper of a mistake in our understanding of physics or more than half the mass in the universe is "something else".

-

Re:Dark Matter?

[CraigParticle]

That's essentially it, yes.

Dark matter has been invoked to explain puzzling observations, within a theoretical framework that has proven pretty trustworthy for everything else so far. Either dark matter is real, or the framework needs a facelift somewhere. Jury's still out on that one.

Let's highlight one example. Consider first the motion of the planets around the Sun, which itself comprises most of the mass of the Solar System. The innermost planets like Mercury and Venus are whizzing around at high speeds to maintain their close orbits. By the time you get out to Neptune or Pluto, they're just crawling along, since they are far away from the Sun. This is all nice and reasonable.

Now when you look at (spiral) galaxies, most of their luminosity (and presumably mass) comes from their inner regions, so you might expect the same kind of rotation pattern; the inner regions would have high rotational velocities, and the outer regions would rotate slowly. But this doesn't happen -- in fact the outer regions tend to rotate every bit as fast as the inner regions! But there's no luminous matter out there to support such rapid motion! There must be something out there that has huge gravitational impact, but without emitting any kind of light. Hence one invocation of dark matter. There are others, but the theme is largely the same.

Some folks understandably find the notion of dark matter distasteful, and are working on modified theories of gravity that have 'appropriate' characteristics on the scale of an entire galaxy. But many consider those "modified gravity" arguments to be unconvincing, ad hoc and distasteful in their own way -- so far.

What is important is that we are learning more and more about our place in the Universe, and uncovering new puzzles that we don't yet understand. And that's what makes it fun. :)

obTolkien

[Xunker]

Obligatory Tolkien (consider yourself warned):

...one ring to orbit them all and in the darkness bind them....

Re:obTolkien

[kilonad]

Obligatory Tolkien

Is that kind of like token Tolkien?

...mmm, the smell of burning karma.

Real explanation

[doogieh]

This ring of stars is the result of a collision, as can be easily proven by observation of Bugs Bunny upon contact with an anvil.

As for the missing mass, that's due to Elmer FUD.

Re:Only 1%?

[jpt.d]

maybe for the reason the slashdot blurb said that you are replying to

Ring of stars

[CaseyB]

Sounds like they've discovered a Kemplerer Rosette. :)

Re:Ring of stars

[coolgeek]

Whew! I'm glad I actually read the page you linked. Thanks to my slight dyslexia I thought the page would be about what Hogan's Heroes used to do to Colonel Klink.

Re:Ring of stars

[merlin_jim]

Sounds like they've discovered a Kemplerer Rosette [burtleburtle.net]. :)

I believe that a Kemplerer Rosette is characterized as being a stable gravitational configuration of bpdoes orbiting a single point at similar distances and speeds in such a way that all bodies are equidistant, and is further characterized in that one could envision a regular polygon of n-sides, where n is the number of bodies, and if one vertex is mapped to the location of one body, and the center of the polygon is mapped to the common orbit location, then all other vertexes will correspond to locations where the other bodies reside.

This ring of stars, being randomly located, would not qualify. In addition, a Kemplerer Rosette is only stable against small perturbations; if the bodies are far enough apart that other gravitational influences grow large with respect to their gravitational influence on each other, then it is no longer stable.

Re:Ring of stars

[MrGeetee]

1. The Universe is finite[1] and there are parts of the Universe that we know to be devoid of mass[2]. The mass in the Universe must therefore be finite.

2. Take a sample region of the Universe. Tally up the amount of visible mass. This gives you a density. Multiply this by the known volume of the Universe[3].

3. Matter is energy. Energy is matter. If antimatter existed in the same quantities as matter, there'd be no you, no me, nothing, nada, rien. Fortunately, antimatter only exists naturally in small quantities[5][6].

[1] There is only so far a photon can travel from one 'edge' of the Universe so the Universe is essentially finite
[2] ie, vacuums
[3] Assume homogeneity first of course[4] ;)
[4] Not necessarily a bad assumption given the uniformity of the Cosmic Microwave Background
[5] And in physics labs around the world :P
[6] Why antimatter doesn't naturally exist in the same quantities as matter is an interesting question in its own right.

Re:Ring of stars

[merlin_jim]

Way to copy that last statement out of your friend's thesis!!!

Actually I made it up on the spot out of memory. Of course, it helps that I modelled them for high school physics class... that and I read all of Niven's books...

When you said "Ring of Stars"...

[RumGunner]

I thought you were talking about the upcoming Oscars! Go LOTR!

.

??? huh?

[_ph1ux_]

Is it just me - or isnt the whole milky way made of stars?

so - they found a ring of stars around a bunch of stars?

Re:??? huh?

[Ironica]

I imagine it's like finding out that Australia isn't actually a separate continent, but part of Asia.

It's not just that there's a ring of stars around a disk of stars, but that that ring relates to the disk in a particular way, which makes the galaxy bigger than previously thought.

I don't get it

[Cyno]

Isn't dark matter simply matter that doesn't emit light? If stars get formed by huge clouds of gas that eventually create so much heat and pressure that it starts a process of fusion, then its more than likely all this dark matter we are talking about is just that, dark matter, dirt, whatever you want to call it. It isn't anything significant other than it isn't radioactive, which is a good thing, IMO.

Re:I don't get it

[jbischof]

No, dark matter is something causing gravitational pull that we cannot locate. It is not neccesarily matter that doesn't emit light.

Nobody knows what dark matter is yet, but there are lots of guesses.

Re:I don't get it

[Christopher Thomas]

Isn't dark matter simply matter that doesn't emit light? If stars get formed by huge clouds of gas that eventually create so much heat and pressure that it starts a process of fusion, then its more than likely all this dark matter we are talking about is just that, dark matter, dirt, whatever you want to call it.

It turns out that the measured effects of dark matter mean that only a small fraction of it can be "normal" matter. Look up "baryonic" and "non-baryonic" dark matter on Google for more information on the subject.

The "normal" component could be anything from white dwarf stars to brown dwarf super-planets to micro black holes to dust and gas, or all of the above. However, that still leaves most of the mass as something else.

Re:I don't get it

[brian0918]

your concept of dark matter is incorrect. dirt is not dark matter. it emits black body radiation. I believe you are also confusing "radioactive" with "radiative".

Re:I don't get it

[Cyno]

All matter has mass and thus gravity.. er I'd like to think it does anyway. :)

Re:I don't get it

[jbischof]

right.... all matter has mass and thus gravity. But maybe something as of yet unclassified also generates gravitational pull. That was all I meant.

The dark matter could be due to neutrinos, black holes, WIMPs, planets(non-light emitting matter like you suggested), other universes, or any other number of bizzare things that scientists have hypothesized.

Re:I don't get it

[Cyno]

yes, but does it have to be some new type of something? Have we accounted for all the normal matter in the galaxy yet? I don't know much about these things, but it seems to me like there's probably many moons and hunks of rock in space that our telescopes just can't see. It wasn't until recently that we even thought there might be planets around other Stars in the galaxy. What's next for our divine intellectuals to discover? Moons around those planets? No, say it ain't so.. Did we take into consideration the mass those moons have and their effect on the Stars, when determining how much dark matter exists?

I don't think its really all that mysterious or difficult, or that we're really all that smart. But I could be wrong.

Re:I don't get it

[Cyno]

black holes are cool! Proof that God is a power gamer. :)

Re:I don't get it

[The Only Druid]

No, some matter could (according to both relativity and quantum physics, not to mention string physics) have not only negative energy (and thus negative mass), but also travel through different dimensions in different directions.

Tachyon's, the result of solving Einstein's equations for an object travelling faster than light, would have negative mass (but positive energy) and would travel backwards through time. Before you say it, yes its impossible to accelerate to lightspeed. On the other hand, there's no reason a certain class of particles couldn't come into existence at faster than light speeds.
Kaluza-Klein particles, a recent idea, are another option for dark matter. They're so-named because they're believed to travel primarily through the 9 folded-up dimensions of string theory. (Kaluza and Klein devised the mathetical methods and theories which explain how string theory functions in an 11 or 12 dimensional universe). These particles, but flitting in and out of "our" four dimensions would only be weakly interacting (and thus qualify as dark matter) but would interact quite powerfully when they were present (due to extremely high mass).

Re:I don't get it

[Anne_Nonymous]

Actually, the universe is made of two types of matter: light matter, and dark matter. Light matter is generally acknowledged to be more savory and delicate in flavor. It can be dry, but when cooked properly, retains the universe's natural juices. Light matter is found in the breast and wings. Dark matter, on the other hand, is found on and near the drumsticks of the universe. It contains a higher percentage of fat and is therefore, often more flavorful and gamey.

Go ahead, ask me another one...

Re:I don't get it

[Cyno]

Now that's the type of answer I was looking for. *applaud* :)

Still over my head, though. :P

Re:I don't get it

[Cyno]

The main problem with phsyics is lately (within the last 50 years) it has been proving most eastern religions correct in their assumptions that everything does have an opposite, that the nature of the universe is bipolar or something. Matter/anti-matter, positive and negative charge, positive and negative energy, etc. It all adds up to the same thing.. we're growing old.

Re:I don't get it

[p3d0]

I like to give the experts a little credit, and assume that they have ruled these things out already.

For instance---and this is entirely fictitious---suppose the galaxies appear to be ten times too small to hold together given how fast they are spinning, and so you conclude they must consist of 90% dark matter that is moons and dust and such. Then, suppose you measure the gravitational lensing, and find that the effective mass is only half what it should be if it were 90% moons and dust. Well, you'd probably have to conclude it's only 40% moons and dust, and 50% pure magic.

That's the kind of thing these scientists do. If someone with actual facts could back me up a bit, I'd appreciate it.

Regardless, it's easy to dismiss a mystery if you don't know the facts involved.

Re:I don't get it

[Cyno]

Actually I'd probably conclude that my tools for measuring needed to be recalibrated. But I get your point. Personally I'd prefer to explain things with science that everyone can understand. When we talk about the Grand Unification Theory any religious nut, politician, or old person can't possibly understand what dark matter is. The very foundation of their system of beliefs would have to be broken for them to accept the possibility of alternate dimensions, etc. Personally I prefer to believe that its all theory until we have some hard cold facts, and attempt to build an hypothesis based on things that have been proven to exist. But that's just me, and I admit I'm weird. :)

Re:I don't get it

[zmooc]

Before you say it, yes its impossible to accelerate to lightspeed.

Only according to a theory that assumes c is a constant while it is not - it's getting slower al the time. It's called CDK. This may also very well mean the red-shift calculations used to determine the speed at which galaxies move away from us are totally wrong which may therefore mean that the universe is not expanding at all (or at least not that fast) which makes the mass-calculations bullshit as well and may very well mean dark mass does not exist and there's just nothing out there. This is a good read about it: http://www.ldolphin.org/bowden.html

Re:I don't get it

[pclminion]

Tachyon's, the result of solving Einstein's equations for an object travelling faster than light, would have negative mass (but positive energy) and would travel backwards through time.

I believe the equation you are referring to is:

E = m*c^2/sqrt(1-v^2/c^2).

If v > c, then (1-v^2/c^2) < 0 and the denominator becomes imaginary. Thus in order for the particle to have real energy it must have imaginary mass.

I think imaginary mass is even harder to envision than negative mass.

Re:I don't get it

[Cyno]

But what happens if we prove these theories to be true? How can we explain to the world that the Universe exists in 11 or 24 dimensions? It contradicts the founding beliefs of most bodies of power. Not that the Universe is extradimensional, but that it is more than what we percieve as reality. How do we create laws for such a land. See what I'm getting at? If science can no longer conform to what society believes to be reality, which is classified as sanity, then society must conform to science. However society does not want to conform and it holds all the keys that unlock science, like money and power. What good is it to know the secrets of the universe when you won't ever be able to tell your parents or grandparents?

Re:I don't get it

[Cyno]

Ooo, I like that :)

I can't even imagine how much imaginary mass I'd have flying 300,000,001 m/s through space. Probably not very much.

Not Dark matter

[jbischof]

Unfortunetly this could not account for dark matter.

The reason scientists believe that there should be dark matter is because of the fact that the stars on the edge of galaxies move faster than they should. According to the measured amounts of mass in a galaxy, the stars on the edges would fly out of orbit at the speeds they are going.

Extra mass on the outer fringe of a galaxy could not contribute to this lack of gravity. I am pretty sure that more than 1% of the galaxy's mass is missing also. But I suppose this goes to show that we never know as much as we think we do.

Checkout the everything 2 node on dark matter for more information.

Re:Not Dark matter

[Anonymous Coward]

actually you got it wrong...here is what it said at everything2.com

There are currently two theories for what dark matter is. The first is the MACHO theory. MACHO stands for Massive Compact Halo Object. This basically means there are large objects orbit on the outskirts of the milky way. These are large objects which weren't big enough to become stars. They are probably about the mass of Jupiter. We know that at least some MACHO's exist by the way they lense or bend the light from a distant star. Although we have observed lensing, it doesn't occur frequently enough to account for all the mass that needs to be in the outer halo.

The other dark matter theory is for WIMPS. A WIMP is a Weakly Interacting Massive Particle. In this case massive means massive on an atomic scale. These particles have a tendency to not interact with other particles. They also cannot radiate away energy. Because of this they can't lose energy easily and orbit at great distances. This would explain the extra mass needed to sustain the rotation of galaxies.

It will be a long time before we have conclusive evidence as to what dark matter is and whether or not it exists.

the first one about MACHOs basicly the theory was that these big objects "around the edge of the galaxy" caused the faster spin...well if you have stars out there it sort of removes the need for machos...anyway i don't know if this accounts for all the dark matter (1%, a mass of 1 billion suns) but it is a good start.

Re:Not Dark matter

[prizzznecious]

Extra mass on the rim alone could not account for the mass discrepancy, but what you're missing is that if scientists couldn't see these stars until now, who knows what else they're missing?

I mean, these are light-emitting stars, even. What about brown dwarf protostars and even dark clouds of space dust?

The observation that stars at the edge of our galaxy don't move fast enough shouldn't incite scientists to come up with new types of matter--it should incite them to find the matter that they've obviously overlooked.

Re:Not Dark matter

[kevlar]

MACHO's are and always have been a scientific excuse for the "missing" matter. I say "missing" (with quotes) because what scientists consider "missing" is simply matter that they cannot SEE versus matter they cannot detect. They CAN detect it indirectly though, which is the fundamental reason they fabricate the need for WIMP's and MACHO's. Meanwhile, a simple solution to this "missing" (or what they really should call "unseen") mass is trillions of massive objects on the planetary scale which are not large enough to produce fusion, and therefore VERY hard to see, but are abundant enough to influence the galaxy's rotation. In essence, MACHO's are an exotic excuse to something lots of astronomers refuse to admit: there's a lot more unseen barionic matter out there.

As a mathematical model, MACHO's are great. In reality though, they're simply barionic matter that we can't see, not some exotic particle. The simple explaination is that there are butt loads (Butt, n: any of various units of liquid capacity; especially : a measure equal to 108 imperial gallons, 491 liters)of planets the size of Jupiter surfing the galaxy.

hmmmm

[CySurflex]

At first I read: "Scientists have found Ringo Star around our galaxy"

Re:hmmmm

[jmb-d]

"Scientists have found Ringo Star around our galaxy"

The tipoff was that it had trouble maintaining anything other than a straight 4/4 rhythm.

Re:hmmmm

[kin_korn_karn]

yeah, but he was still a step above Pete Best. ever hear the Anthology 1 stuff he played on? damn, he sucked.

Hmmm...

[CommieLib]

Maybe the ring makes them invisible? Maybe it binds them all? Maybe it...oh, never mind.

Space and Science can explain anything...

[screenbert]

Mom used to tell me, "Becuase I'm the mom and your the son and that's why"

I explained to her logically using space and science that "You're right, You're the mom and I'm the son and we all know the world revolves around the sun".

Likewise invisable stars explain dark maatter.

Dark Matter

[FuryG3]

Somewhat offtopic:

In the world of diagnosing dark matter, scientists think that neutrinos could make up a good hunk of it.

http://www.aip.org/enews/physnews/2002/split/586 -1 .html

I heard about this on NPR's Talk of the Nation: Science Friday last week. What i heard was: in order for neutrino's to change from one type to another, they must have a small ammount of mass, and even if you give neutrino's a tiny tiny tiny ammount of mass, they suddenly account for a good hunk of the dark matter out there.

I know nothing about any of this, so if someone could go into further detail it'd be great.

Re:short answer

[yobbo]

Could this be part of the elusive 'dark matter' talked about so much lately?

Yes.

Hey look at me, I provided an answer with absolutely no evidence to back it up, gimme a +1 informative!!

What if it's the other way around?

[core plexus]

In the article: "If the ring turns out to be due to a satellite galaxy, it would mean that we are seeing the Milky Way cannibalizing a small galaxy and incorporating it into the galactic disk..." But what if it's the other way around?

Man Gets 70mpg in Homemade Car-Made from a Mainframe Computer

Re:What if it's the other way around?

[merlin_jim]

In the article: "If the ring turns out to be due to a satellite galaxy, it would mean that we are seeing the Milky Way cannibalizing a small galaxy and incorporating it into the galactic disk..." But what if it's the other way around?

Wouldn't that be like the researcher who, several years ago, proposed the theory that The Odyssey was not written by Homer the blind poet but was in fact written by a completely different blind poet named Homer?

Re:What if it's the other way around?

[core plexus]

No, they collapsed without any ring of stars to influence them.

But it sure could be.

Re:dark matter

[EvanED]

How is this redundant? The other answer just said "no".

Re:short answer

[Computer!]

Could this be part of the elusive 'dark matter' talked about so much lately?

I was wondering who was talking about dark matter so much lately, and it was you two! Problem solved.

Re:short answer

[gewalker]

3 points for concise and correct answer, -1 for missing important details left out.. Not quite so short answer follows:

No, because dark matter is thought to be the explanation for galaxies moving apart faster than conventional explanations, so dark matter is assumed to exist and cause a negative gravitional attraction (negative mass, not anti-matter), to explain observed behavior.

Even if you assume postive vs. negative matter is not the issue, the ring around the galaxy is much to small in mass to make much of a difference anyway (much smaller that assumed dark-matter).

This Just In ...

[handy_vandal]

... the universe is "really, really big."

Re:This Just In ...

[smnolde]

"My God! It's full of stars!"

Re:This Just In ...

[glenebob]

It is also vastly hugely mind-bogglingley big.

Re:short answer

[The Only Druid]

You're somewhat incorrect. What you refer to - matter with negative energy or "quintessence" - is not what is meant by dark matter. It is "dark energy". I know the name seems to imply similarity or identity, but they're different.

Dark matter is the [largely] undetectable matter that is proposed to contain a significant portion of the mass of the universe; the mass which is unaccounted for by visible matter. There are three main [current] theories about this:

MACHOs. I forget what the acronym stands for, but these are essentially hugely massive particles which are still small. As such, they account for a significant amount of mass without occupying much volume in space. This lack of significant volume (and their relative seperation) makes them difficult to detect.
WIMPs. This acronym was chosen to compete with MACHOs, actually, in a fit of playfullness by scientists. It stands for Weakly Interacting Massive Particles. These are actually quite similar to machos, but are formulated differently mathematically.
Massive neutrinos. Without getting too much into theory, there are many types of neutrinos. If some of them are at all massive (and current experiments suggests that they are) then their massive numbers could account for a significant amount of the missing mass.

Re:No, no dark matter.

[Randolpho]

Space.com slashdotted? That'll be the day.

Re:short answer

[merlin_jim]

Could this be part of the elusive 'dark matter' talked about so much lately?

Yes.

Most scientists believe that dark matter makes up 80 - 95% of the total gravitational mass of the galaxy, and probably the universe.

Dark matter is simply the term given to matter that we haven't observed yet, except indirectly through its gravitational effect.

This is certainly some portion of the dark matter. But I wouldn't say a significant part, or even a part really worth mentioning. While the dark matter is almost definitely comprised of several different sources, it seems certain to me that there is an entire class of gravitational objects that we have yet to observe, and this is the cause of the dark matter. Whether its dark stars, black holes, heavy neutrinos, or some even more strange and cosmic form of matter I don't know. It could be all of those and more.

Point being, if the dark matter within the Milky Way is only 80% of the mass of the galaxy, and not say 95% as some researchers suggest... this would make it 400% of the mass of the observed portion of the galaxy. These stars are, according to the article, 1% of the mass of the (previously) observed portion of the galaxy. Which makes them 0.25% of the mass of dark matter required to account for gravitational effects that are otherwise unexplained. If dark matter turns out to be a significantly larger percentage, such as 95%, then these stars only account for .05% of the mass of dark matter.

For those who question the value of determining either the cause or the exact amount of dark matter in the universe, this debate is pivotal for determining the final fate of the universe. So far our calculations of the total mass of the universe, including the dark matter, are riding the knife-edge required to make the universe exactly stable. If there is a little more mass than this, then the current expansion of the universe will one day reverse, until the universe contracts back to a singularity. If there is a little less mass than this, then the current expansion of the universe will continue infinitely.

This is all according to current theory on the creation and eventual fate of the universe and is subject to change with brilliance, genius, and persperation.

Re:short answer

[Anonymous Coward]

Now try to find the elusive gray matter.

Not really full of stars ...

[handy_vandal]

... more like it's littered with stars.

How Really is Really?

[handy_vandal]

We need a new unit of "really big" ... the "mega-really" ... or better yet, the "way really".

Re:Dark Matter

[freeweed]

I've personally never been able to understand how neutrinos DON'T have mass. I copped out of physics after 2 years, so I missed most of the good math, but... ..since mass = energy, and neutrinos definitely have energy (else how could we measure them? how could they possibly interact with other particles, however weakly, if they didn't?), neutrinos have mass.

Any physics majors out there?

oh, I know what it is

[Tablizer]

Damned Warchalkers

more data needed

[1fitz2many]

I didn't notice any mention of velocity data from the article, or what method was used to determine distance. This would be important in understanding the ring's history.

However, one could speculate that if these stars are indeed part of a ring, the ring may have formed through a collision with another galaxy. For an example, check this out. Here is another example of a ring galaxy.

Big Bang Nucleosynthesis

[lythari]

Baryonic matter cannot account for dark matter because of big bang nucleosynthesis (BBN). BBN gives us a fairly accurate esimation of the baryonic matter density of the universe. The result derived from BBN agrees with the mean mass density obtained by summing the visible matter from a representative sample of galaxies. Thus this suggests that dark matter is non-baryonic.

Re:Dark Matter

[p3d0]

Obviously they mean "rest mass". That is, the mass when the particle has zero velocity.

Not the Dark Matter.

[Axe]

Distribution of the Dark Matter must be heavily cusped in the middle of the galaxy to account to the observed rotational curves. It can not be explained by far away objects.
The second problem is that there must be a LOT of DM.. Not a few faint stars..

Re:Not the Dark Matter.

[955301]

So what do you think about the hypothesis that dark matter is the matter in an adjacent universe who's properties cause side affects in our own. This would imply that gravity is not constrained to one space-time, but also affects those universes around our own.

I can't help but think something like this, in combination with the theory that black holes in one universe are the points of origin for adjacent universes. I've heard it said before that most galaxies have a black hole at the center at the least?

That might account for both of your points, along with the observation that the universe is constantly expanding (matter continuously arriving through the black hole in another universe).

Re:Not the Dark Matter.

[Axe]

Among the current theories that are more "exotic" then WIMPs (neutralino and friends) those that deal with the breakdown of the Newton law at large distances look like the most promising..
Many people do not realise that general relativity equation do have some fairly heavy assumptions - like requirement for the equations to be of no higher then second order. It may be possible to write a different theory that will lead to non-linear beahviour of acceleration for small forces. That would explain rotational curves (the most solid evidence for dark matter) without dark matter.
Nevertheless, WIMPs involve less new assumptions, at elast at this moment, so Brother Occam tells us it must be true.. ;)

The Milky Way is a Barred Spiral

[Anonymous Coward]

For a long time, I've heard that some astronomers think the Milky Way is a barred spiral galaxy. It's of course very hard to tell looking out from within. This discovery would tend to vindicate that view. What they have detected is the ring of stars that form the faint spiral around the outer periphery. We live at the far end of one of the bars. Have a look at this photo of NGC5850 and you can see what I'm talking about. It's "ring" is a bit more prominent than ours though. Google has more.

That explains it.

[g4dget]

Astronomers have discovered portions of what appears to be a giant, donut-shaped ring of previously unseen and surprisingly old stars surrounding our Milky Way Galaxy.

Wow, that explains why he made the international sign of the donut.

probably not

[rebelcool]

MACHOs are enormous objects like supermassive blackholes. There arent many of them, if they actually exist.

The reason there can't be many of them is we'd probably have detected them already by gravitational lensing. So whatever it is thats out there, its really heavy, and theres not many of them because so far we havent seen any lensing from objects near the edge of the galaxy.

In order to make up the necessary 'missing matter' from things like faint stars, neutron stars or dead stars, there would need to be alot of them.

While we're on theoretics, its also possible the phenomenon is related to dark energy, which has recently (within the past couple months) been nearly proven to exist by studying several lensing objects. 'Dark Energy' is likely whats responsible for the increasing rate of expansion in the universe. Its effectively a kind of anti-gravity. Its nature, such as where it comes from, is still totally unknown.

LOTR?

[bogado]

This gives a hole new dimension to lorg of the ring. :-)

In Soviet Russia...

[Slur]

...Dark Matter detects YOU!

Re:short answer

[MillionthMonkey]

>>Could this be part of the elusive 'dark matter' talked about so much lately?

>Yes.

I vote no. Stars are luminous and dark matter is not luminous by definition. This could be said to be part of the "missing matter", but not the "dark matter". Argumentum ad lexicon, QED.

Anyway, isn't dark matter supposed to be a hypothesized explanation for why stars in spiral arms are orbiting the centers of galaxies more quickly than can be accounted for by the observed abundance of luminous matter? I'm not familiar with the gravitational properties of a ring-shaped mass distribution, but a ring of stars surrounding the outer rim of the galaxy seems to be in the wrong place to have any explanatory power for the high orbit velocities of stars that are well within the ring. You want to find something heavy that's within their orbits.

Re:Is it just me....

[JoeRobe]

I don't think it's a huge waste of resources. We can approximate the mass of the universe by looking at rotation curves of galaxies, luminous matter, etc. It is precisely the fact that we can't see some of this mass which we know exists that makes the dark matter problem so interesting. We can detect it - that's easy - just look at rotation curves. The fact that we can't see it doesn't mean we can't detect it...

here's the problem

[rebelcool]

even if you filled the outside of the galaxy with a shell of dead rock, it wouldnt account for the missing mass. There is *alot* of missing mass. Plus itd be easy to spot that, because little light would get through it.

Others suggest alot of neutron stars spinning around out there, also not likely. We'd have noticed them, either by an inordinate amount of nearby pulsars, or simply from gravitational lensing. Same goes for dead hunks of carbon. To make up the missing mass, there would have to be many of these things. And with many of them, the chance of spotting several would be high.

The macho theory suggests there COULD be a *few* but *extremely* massive objects wandering around out there. Something like supermassive blackholes, or something else. If there were a few, and they emitted no light (likely), then they'd be easy to miss.

The other theory suggests that there is some kind of exotic matter which we haven't discovered yet that emits no known form of radiation, but may indeed generate gravity. This is also possible, as the newly discovered 'dark energy''s origins are also unknown. The confirmation of dark energy (which is recent) is what drives the expansion of the universe, and is indeed some kind of 'anti gravity'. Very interesting, but very strange. And we have no idea where the hell it comes from.

Speculation

[cardshark2001]

Speculation is at least reasonable in an area of astrophysics where the practicioners themselves will gladly admit to anyone who won't tell them to shut up because no one likes to talk about his job. This is my opinion, at least.

I have an idea that I've never really read anywhere, and I've always wondered why. What if gravity is a source of both attraction and repulsion, but the attraction affect is much stronger within a certain locus, such as within a galaxy? Now, take that idea and imagine a sort of fractal effect, leading to clusters of galaxies, and clusters of clusters.

So the affect that pushes galaxies away from each other is also gravity, but Newton's law gets bent over intergalactic distances.

I'm stepping all over everyone's toes here, because I've had only basic physics coursework, so I apologize now to any astrophysicists I might have offended.

Not Actually Tolkien Ring

[Ilan Volow]

Technically it's a star topology.

Those are not stars!

[Snaller]

It's the barrier around the galaxy! StarTrek was right all these years!

Ten Thousand Things

[handy_vandal]

Maybe an infinite number of parallel universes are not small but crowded?

"From the One come the Two
From the Two come the Many
From the Many come the Ten Thousand Things"
- Lao Tzu

"Yeah, and then you have to find some place to put them."
- Paul Busch

Re:Warning - Cretinist reference

[zmooc]

Could you please post some links for your arguments? The only arguments against the CDK-theory I've found so far are on the same level as yours; incomplete. I'm very willing to believe the oppossite, but so far haven't found any theory that proves CDK wrong with good arguments. How do supernova light curves (what are they?) prove CDK wrong? As far as I know, the calculations were based on statistical evidence which therefore do "ignore" a lot of data but all data points in that direction and most certainly does not prove CDK wrong. How would their calculations lead to earth being something it clearly was not [4K yrs ago]?

Apart from that, the CDK theory potentially solves a lot of problems and mysteries about dark matter and the expansion of the universe.

Dark Matter and microlensing.

[Christopher Thomas]

...wait. Isn't dark matter supposed to still have mass and gravity? So any dark matter of sufficient size would cause microlensing, not just baryons, no?

Only if it's concentrated into very compact clumps.

If it's a halo of low-mass chargeless particles, clumps would be much larger (think "galaxy-sized or bigger"). Such dark matter would not be directly visible within our galaxy, though "dark galaxies" or larger blobs of dark matter could be seen by lensing of distant quasars. Searches for "dark galaxies" have been underway for a while (though the main purpose is to look for ordinary galaxies that are just dim enough not to be seen that far away, if I understand correctly).

Things like "dark energy" might not clump at all (I'd have to look that up to confirm it, though).