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

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?

[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.

Ring of stars

[CaseyB]

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

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.

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

[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

[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

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.

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!!

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: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.

This Just In ...

[handy_vandal]

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

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: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.

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.

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.

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.. ;)