Astronomers Think They've Spotted a Galaxy That's 99.9% Dark Matter (cnn.com) 71
Astronomers have spotted a galaxy they believe is made of 99.9% dark matter, reports CNN — and it's so faint, it's almost invisible:
CDG-2, which is about 300 million light-years from Earth, appears to be so rich in dark matter that it could belong to a hypothesized subset of low surface brightness galaxies called "dark galaxies," which are believed to contain few or no stars.... [Post-doctoral astrophysics/statistics fellow Dayi Li at the University of Toronto was lead author on a study about the discovery, and tells CNN] There is no strict definition of dark galaxies... but their existence is predicted by dark matter theories and cosmological simulations. "Where exactly do we draw the line in terms of how many stars they should have is still ambiguous, because not everything in astronomy is as clear-cut as we like," he said. "To be technically correct, CDG-2 is an almost-dark galaxy. But the importance of CDG-2 is that it nudges us much closer to getting to that truly dark regime, while previously we did not think a galaxy this faint could exist."
To observe CDG-2, the researchers used data from three telescopes — Hubble, the European Space Agency's Euclid space observatory and the Subaru Telescope in Hawaii — along with a novel approach that involved looking for objects called globular clusters. "These are very tight, spherical groupings of very olds stars, basically the relics of the first generation of star formation," Li said. Globular clusters are bright even if the surrounding galaxy is not, and previous observations have shown a relationship between them and the presence of dark matter in a galaxy, Li added. Because CDG-2 appears to have very few stars, there must be something else providing the mass that the clusters need to hold themselves together. Li and his colleagues assume that the source of the mass is dark matter.
The researchers found a set of four globular clusters in the Perseus Cluster, a group of thousands of galaxies immersed in a cloud of gas and one of the most massive objects in the universe. Further observations revealed a glow or halo around the globular clusters, suggesting the presence of a galaxy... Astronomers believe, Li explained, that after the formation of the clusters early in the galaxy's existence, larger surrounding galaxies stripped it of the hydrogen gas required to make more individual stars like our sun. "The material that this galaxy needed to continue to form stars was no longer there, so it was left with basically just a dark matter halo and the four globular clusters." The process, he added, would leave behind a skeleton or ghost of "a galaxy that pretty much just failed." As a result of this formation mechanism, the galaxy only has 0.005% of the brightness of our own galaxy, Li said...
Studying potential dark galaxies is important because they provide nearly pristine views of the behavior of dark matter, according to Neal Dalal, a researcher at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, who was not involved with the study.
Robert Minchin, an astronomer at New Mexico's National Radio Astronomy Observatory, told CNN that "it seems likely that other very dark galaxies will be found by this method in the future."
To observe CDG-2, the researchers used data from three telescopes — Hubble, the European Space Agency's Euclid space observatory and the Subaru Telescope in Hawaii — along with a novel approach that involved looking for objects called globular clusters. "These are very tight, spherical groupings of very olds stars, basically the relics of the first generation of star formation," Li said. Globular clusters are bright even if the surrounding galaxy is not, and previous observations have shown a relationship between them and the presence of dark matter in a galaxy, Li added. Because CDG-2 appears to have very few stars, there must be something else providing the mass that the clusters need to hold themselves together. Li and his colleagues assume that the source of the mass is dark matter.
The researchers found a set of four globular clusters in the Perseus Cluster, a group of thousands of galaxies immersed in a cloud of gas and one of the most massive objects in the universe. Further observations revealed a glow or halo around the globular clusters, suggesting the presence of a galaxy... Astronomers believe, Li explained, that after the formation of the clusters early in the galaxy's existence, larger surrounding galaxies stripped it of the hydrogen gas required to make more individual stars like our sun. "The material that this galaxy needed to continue to form stars was no longer there, so it was left with basically just a dark matter halo and the four globular clusters." The process, he added, would leave behind a skeleton or ghost of "a galaxy that pretty much just failed." As a result of this formation mechanism, the galaxy only has 0.005% of the brightness of our own galaxy, Li said...
Studying potential dark galaxies is important because they provide nearly pristine views of the behavior of dark matter, according to Neal Dalal, a researcher at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, who was not involved with the study.
Robert Minchin, an astronomer at New Mexico's National Radio Astronomy Observatory, told CNN that "it seems likely that other very dark galaxies will be found by this method in the future."
Re:This constant assumption that dark matter is ri (Score:5, Informative)
The "dark" nomenclature just marks the edge of where our experimental apparatus can no longer function. They know that dark matter exists, because there isn't enough regular matter to create enough gravity to keep a spinning galaxy like the Milky Way from flying apart. They can also see gravitational lensing occurring where one galaxy is behind another, but the closer galaxy doesn't have enough gravity from regular matter to bend light that much.
Dark energy is more if-fy, but they're pretty sure there is such a thing.
Re:This constant assumption that dark matter is ri (Score:4, Insightful)
You mean that you just don't believe in any measurement that is not made directly using the electromagnetic field.
If there are measurements made via the gravitational field, you don't believe it unless somebody figures out how to replicate the measurement directly using electromagnetism. If there is a physical phenomenon in this universe that simply never interacts with the electromagnetic field, well then it just will never exist for you.
Re:This constant assumption that dark matter is ri (Score:4, Informative)
If there are measurements made via the gravitational field, you don't believe it unless somebody figures out how to replicate the measurement directly using electromagnetism. If there is a physical phenomenon in this universe that simply never interacts with the electromagnetic field, well then it just will never exist for you.
Well, it doesn't interact with the weak or strong force either in a way that's been measured yet, either. Neutrinos don't interact with the EM field but they are now routinely detected.
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I am not trying to take sides here as I do not know the real truth.
If there is a physical phenomenon in this universe that simply never interacts with the electromagnetic field, well then it just will never exist for you.
Are there any phenomena that do not involve electromagnetism that we are currently 100% of aware of and know to be true? I am wracking my brain and I am having a very hard time thinking of anything at all that does not interact with an electromagnetic field.
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Dark matter, whatever it is, is known to be true. So far, nobody has found any interactions with electromagnetism.
My point was, a lot of people point at that situation and say: "We can't see it! So it must not exist, and you are stupid and ignorant for hypothesizing that it could exist!"
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"If there are measurements made via the gravitational field, you don't believe it unless somebody figures out how to replicate the measurement directly using electromagnetism."
Gravity is a theory, not a fact.;-)
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"...is just a made up explanation for that. There is no evidence it exists."
The idea of dark matter is not that dark matter exists, it's that the dark matter theory is a placeholder used to explain the observations we see in the universe that are contrary to the physical understandings as we know them currently. The physicists are essentially saying there's a bunch of stuff we just can't explain, and dark matter is a concept that they refer to until we can finally figure out the bigger picture. It may be a while.
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Just replace all statements of "dark matter" with "lots of block holes". There's probably far more black holes than visible stars. And not too surprisingly, there is some galaxies with an enormous amount more black holes.
Re: This constant assumption that dark matter is r (Score:5, Informative)
No, neither the block holes nor the black holes appear to be a valid explanation.
If they were, we'd be seeing a phenomenon called "gravitational microlensing" much more often than we do. This happens when the black hole passes in front of something from the background and that something flares up briefly as if someone has put a giant loupe in front of it.
Since we don't see these microlensing events all that often, the dark matter is likely made up of clouds of particles that interact very weakly with our world except through gravity.
Incidentally, 300m ly is very, very close, that's "local" distance. So it is a very novel and interesting observation if is confirmed.
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I guess that make this new find an excellent candidate for identifying a higher concentration of microlensing then.
Re: This constant assumption that dark matter is (Score:2)
No, at 300M light years any microlensing will probably be undetectable even in favorable circumstances. We've mostly seen it from local, galactic MACHOs [wikipedia.org] in the direction of the Magellanic clouds, IIRC.
This could be a great example of a DM galactic gravitational lens, as there will be almost no foreground light or absorption of the background from the galaxy itself though - if there is a luminous object far behind it.
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Oh, that easily leaves open DM being black holes then.
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No, not really. You have to assume that the distribution of black holes is really uneven and that our part of the Universe is a huge exception in order to do that, and there is absolutely no evidence any of these is true. And the black hole business is a small part of the evidence, so you must address everything else, which is a lot.
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It sounds like you're making even more assumptions than me. Black holes seem perfectly plausible from what you've said.
Re: This constant assumption that dark matter is (Score:2)
Like I said, it is a question of evidence, which overwhelmingly points to DM not being black holes.
You are, of course, free to dismiss the evidence or disagree with it, this is the fashionable thing to do in the pre-singularity age.
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Doesn't seem to be anything overwhelming at all. There just isn't the evidence as you've presented it. You clearly stated how difficult it is to see microlensing. That leaves plenty of leeway for black holes to fully explain dark matter.
Re: This constant assumption that dark matter is (Score:2)
like I said, you can stick to your beliefs or show us your math.
we can argue the math, but only if it is there.
cheers,
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. There just isn't the evidence as you've presented it.
No, there is evidence. You refuse to accept it.
You clearly stated how difficult it is to see microlensing. That leaves plenty of leeway for black holes to fully explain dark matter.
There is not a lot of leeway. Scientists have looked at the evidence and determined black holes do not explain dark matter. You don't know the evidence therefore there is a lot of leeway for you.
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And like I said, I'm just putting your statements together. Which appears there isn't enough evidence for the maths. There certainly isn't any evidence of mythical gravity-only matter in particle experiments. It's all a lot of guessing at this point.
Re: This constant assumption that dark matter is (Score:2)
yes, I pointed out why you're wrong, but as the global warming denialists, the moon hoaxers and the vaccine hoaxers have shown us, it is impossible to change the uninformed opinion of a believer in their own "truf", so I gave up.
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Well, as the saying goes, extraordinary claims need extraordinary evidence. When this mythical matter of yours is ever discovered I'll happily come on board. Until then, I'll leave you with your hoaxers. You seem strong on that juice.
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Black holes are not the extraordinary claim though is it. That's the mundane ordinary matter claim. Albeit, out of reach. So it's on you to prove how some etherial untouchable matter, that we supposedly live amongst, could ever exist. You're the one out on a limb here.
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Again your claim it is black holes. Why don't you provide evidence first instead of challenging everyone to prove you wrong? In the same way, I could claim it is magic fairy dust. Prove me wrong.
You're the one out on a limb here.
No I am not. Asking you to provide evidence of your claims seems a bridge too far for you.
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Is the proposed 'dark matter' stuff that behaves unusually and so is something not understood, or is it just normal matter, perhaps of unexpected chemical or nuclear composition (for example with lots less hydrogen around), without the energy to illuminate itself.
Re: This constant assumption that dark matter is (Score:3)
It is something that ignores the electromagnetic, weak and strong interactions, kind of like a neutered neutrino. And there may be many kinds of "it".
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Dark matter is placeholder for matter that has been shown to exist but is non-luminous. However it does not seem to react like normal matter (baryonic) in other ways. The main issue is dark matter accounts for a lot of missing matter. If you take all the estimated stars and planets and moons in the Universe then multiple by 5X, that is the amount of matter that is missing. It is not a small amount.
The other thing people seem not to understand is that this missing matter is not one scientist or a small tea
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"It's like string theory. Just made up stuff " That's all of modern mathematics. Sometimes we verify that some equations do a damn fine job modeling bits and bobs of the Universe. The bit and bobs are out there, the math is in our heads.
So we create a mathematical theory of Dark Matter. You can just call it the Theory of Gravity. The theory is just made up and in our heads. Yet it does a damn fine job of explaining some bits and bobs of the Universe.
Once we have everything all figured out, we'll get back to
Re: This constant assumption that dark matter is r (Score:4, Informative)
Dark matter is a name for a class of phenomena that are only observable by their gravitational influence on other things.
If something isn't visible, it is invisible, that is, "dark".
If it has mass, it is matter.
Hence, "dark matter", until a better understanding and a better name appears.
Ok?
Here's a cookie and a glass of milk for you, calm down.
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Re: This constant assumption that dark matter is (Score:2)
No.
First, on a galactic scale its distribution is far beyond the visible galactic mater, which means it is where star formation never happened, and second (on top of being invisible) it is distributed in a way that suggests whatever it is made of practically doesn't interact with Standard Model matter or with itself, which of course precludes it being a part of a "burning" matter in stars.
Second, this pattern is repeated on a massively intergalactic scale:
https://en.wikipedia.org/wiki/... [wikipedia.org]
You can literally s
Re: This constant assumption that dark matter is (Score:2)
And, of course, there's the problem that it is A LOT. 20% visible vs 80% invisible, or dark matter by mass. With jwst fully operational we'll see better maps soon.
https://www.nature.com/article... [nature.com]
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Re: This constant assumption that dark matter is (Score:2)
Yes, I do.
I have also seen actual supernova remnants with my own eyes and can even calculate how much supernova material is there and how does it wrap around the galactic center of gravity.
You don't have to believe me, you can do the calculations yourself and verify if there is enough supernova material to form the observed DM halo around your average galaxy, or will it go around it as it does.
You need basic mechanics for that, Zwicky did it back before gravity lensing was even a thing. Here, from the horse
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You know when a star goes supernova it blows material light years away and some of that material is flying around endlessly
The problem is the mass distribution in the Universe would have to be very different in terms of location and composition. Take our solar system. It exists because the Sun is 99.86% of the mass of the solar system and is mainly hydrogen. If planets and moons were 5X the mass of the Sun, they would not revolve around it.
Also the life cycle of elements is hydrogen creates helium and other elements in nuclear fusion. Heavier elements are created in supernova. There is no natural process I am aware that breaks
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Dark matter is estimated to be more than 5X the mass of normal matter. That is a lot of missing matter that came from a supernova. By comparison, the Sun is 99.86% of the mass of the entire solar system. The rest of the non luminous solar system is 0.14%. If we were to hypothetically increase the mass of planets and moons to 5X to the Sun to account for dark matter, the problem is the solar system no longer revolves around the Sun.
Besides mass affecting orbits, another issue is with what we know about stel
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OK Einstein, propose an alternative explanation for the results that isn't weirder than dark matter/dark energy.
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Well, there's what I call "adapted" MOND [wikipedia.org] - a simple explanation that keeps "adapting", that is, getting more and more complicated in a Ptolemaic way as evidence accumulates.
It lacks any physical interpretation, but then so did the Kepler laws before Newton and the Lorentz transformations before Einstein, say its proponents.
Unlike the former two, however, which describe all relevant known phenomena well, there is physical evidence that contradicts the modified dynamics (and its more "physical" variants of "m
Re:This constant assumption that dark matter is ri (Score:5, Informative)
Every time some random Dunning-Kruger slashdotter displays his ignorance to the entire Internet, a kitten dies somewhere.
In astronomy and astrophysics, the term "dark" doesn't mean the same thing as it does in common english, just like the term "metal" doesn't mean the same thing as it does in common english. Astrophysicists and astronomers use the term "metal" to describe any element that is neither hydrogen or helium. To them, there is hydrogen, helium, and metals, which include things like carbon or oxygen.
In the same way, astronomers and astrophysicists use the term "dark" to describe anything that has observable, and even measurable, effects but has not been demonstrated to fit in any current theory. There is no "dark" matter and "normal" matter, because "dark" matter is "normal" matter in all the current hypotheses about it. No astronomer or astrophysicist claims, or has ever claimed, otherwise. They know there is unaccounted for mass in the universe because they can observe it and even measure it through its gravitational effects on stars and galaxies, but they have no current theory on what this mass actually is, only hypothesis. Hence their use of the word "dark".
The same thing applies to dark energy. They observed that the universes' expansion is accelerating, and according to the current theories of physics such acceleration requires a force, but they have no current theory on what this force is, hence their use of the word "dark" force, or more commonly dark energy.
JFC the worst kind of ignorants are the ones who are convinced that they know better than thousands of people who've worked and studied in a field for decades and add on knowledge that's been accumulated for centuries. For fuck's sake, stop killing kittens and shut the fuck up when you don't know what you're talking about.
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Thank you for setting this straight, as the term 'dark' in these comments has been used more than a few different ways.
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"In astronomy and astrophysics, the term "dark" doesn't mean the same thing as it does in common english, just like the term "metal" doesn't mean the same thing as it does in common english. Astrophysicists and astronomers use the term "metal" to describe any element that is neither hydrogen or helium. To them, there is hydrogen, helium, and metals, which include things like carbon or oxygen."
AFAIK 'Metals. include everything created by fusion, and the non-metals is stuff that was around since (just after)
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Ah, but the first material that pops out of a star is helium.
I have to say, irrespective of the definition, this terminology is a strange one.
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And it's even possible that dark matter / energy could consist of different things, so there might not be just one type of matter or energy that currently has the "dark" label.
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Most of it is aliens flying around in stealth spaceships. We can't spot them, except that they haven't figured out a way to hide their mass.
So galaxies with more DM are more technologically developed than the others. In this all-DM galaxy they must have used up almost everything else to build ships.
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They didn't call if dark to obfuscate, sound cool, or pretend they are superior to you. They called it dark it's fundamental defining property is that while they could infer it's existance they could not observe it with any of their instruments - all w
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Every time some random Dunning-Kruger slashdotter displays his ignorance to the entire Internet, a kitten dies somewhere.
We must be amid a major feline extinction event.
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Why is it hard to imagine a particle that doesn't respond to the weak, strong or electromagnetic force?
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Why is it hard to imagine a particle that doesn't respond to the weak, strong or electromagnetic force?
Because they don't want to.
Perhaps all their imagination is all used up on other things, like people who suffer the ill effects of 5G from nearby cell towers that haven't even been activated.
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Why is it hard to imagine a particle that doesn't respond to the weak, strong or electromagnetic force?
Scientists can imagine such a particle. The problem is that such a particle does not conform to rules and observations formulated over centuries. It may be dark matter/energy represents a whole new branch of physics. While mass discrepancies go back centuries, dark matter/energy started in the 1970s. More and more observations have confirmed it rather than dismiss it.
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it's constantly adjusted to match experimental data.
Some of us think basing our beliefs on evidence is a good thing.
Unlike tradition and revelation, where new evidence is something to be ignored or explained away.
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There is no evidence it exists.
Well that's a lie. There is plenty of evidence it exists. That was the whole point of naming it dark matter and dark energy. They can be measured. They have been measured by multiple teams across multiple countries, languages, etc.
Saying a galaxy is 99.9% something that we have no clue if even exists seems insane.
Scientists knowing it exists and knowing what it is exactly are two different things. Since ancient times, people were aware that objects had electric charges; it wasn't until 1897 that the electron was formally discovered. The Higgs Boson was theoretical since the 1960s; it was f
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No, it's just some of that "darkness on the face of the deep" left over from Creation.
God didn't need all of that "waste and void" to shape into what He wanted for our universe, so He left bits of it in its natural form here and there.
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Yesterday (Score:2)
Yesterday, upon the stair,
I met a man who wasn't there!
He wasn't there again today,
I wish, I wish he'd go away!
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maybe a darkmatter galaxy (Score:2)