Astronomers Find 19 More Galaxies Missing Their Dark Matter (astronomy.com) 90
A reader shares a report from Astronomy.com: Astronomers have discovered 19 more galaxies missing their dark matter. Instead of dark matter, these strange galaxies are mainly filled with regular matter, like the protons, neutrons, and electrons that make up everything we're familiar with. The new find, published November 26 in Nature Astronomy, bolsters the controversial recent discovery of two other galaxies without dark matter. The mysterious substance accounts for most matter in the universe, and it's thought to be the primary component of all galaxies -- as well as the main driver of galaxy formation in the first place. So, finding so many galaxies without the exotic matter suggests astronomers are missing something major about how galaxies form and evolve.
"This result is very hard to explain using the standard galaxy formation model," said lead author Qi Guo of the Chinese Academy of Science in a press release, "and thus encourages people to revisit the nature of dark matter." The latest batch of galaxies missing dark matter was discovered when Guo and her team explored the nature of 324 dwarf galaxies using data from the Arecibo Observatory in Puerto Rico and the Sloan Digital Sky Survey. With this data, they followed in the footsteps of Rubin and Ford, studying how fast hydrogen gas rotates around each galaxy. They also calculated how much normal matter -- in the form of both gas and stars -- they contained. After crunching the numbers, Guo and her colleagues determined that, of the 324 dwarf galaxies they investigated, 19 of them contain enough visible matter to solely explain the motions of the galaxies' hydrogen. In other words, a lot of dark matter seems to be missing from these galaxies.
"This result is very hard to explain using the standard galaxy formation model," said lead author Qi Guo of the Chinese Academy of Science in a press release, "and thus encourages people to revisit the nature of dark matter." The latest batch of galaxies missing dark matter was discovered when Guo and her team explored the nature of 324 dwarf galaxies using data from the Arecibo Observatory in Puerto Rico and the Sloan Digital Sky Survey. With this data, they followed in the footsteps of Rubin and Ford, studying how fast hydrogen gas rotates around each galaxy. They also calculated how much normal matter -- in the form of both gas and stars -- they contained. After crunching the numbers, Guo and her colleagues determined that, of the 324 dwarf galaxies they investigated, 19 of them contain enough visible matter to solely explain the motions of the galaxies' hydrogen. In other words, a lot of dark matter seems to be missing from these galaxies.
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Just pick a one sided topic. Say bashing China. Everyone will mod you up.
If you pick climate change, or Trump. There are people on both sides so it's more based on luck. But everyone hates China so spam away.
Good luck.
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Everyone except you, obviously.
Re: Lol. In an emergency, the devil lets flies bai (Score:1, Informative)
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No they don't. Not even close. Not even in the same ballpark, town, state, or country. Most stupid Americans don't even know the different ethnic groups in China well-enough to apply any kind of racial stereotype. There used to be an enormous amount of racism against "the Chinese" directed against immigrants a hundred years ago, not that many of the Americans of the day were much more-knowledgeable about the people they hated. Today's American scarcely remembers such things.
Re: Lol. In an emergency, the devil lets flies ba (Score:2)
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That is generally correct.
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Good grief. Got a chip on your shoulder? Who pays you to write this garbage? Nobody said anything about China in this decidedly-not-about-China topic except you and some stupid AC. They just HAD to bring it up, apparently because we haven't gone far-enough off-topic yet.
Nobody proved anybody's point. The AC has such a hard-on for protecting the Chinese government that he has to complain about all the people calling out the PRC for . The only point he has is that he's obsessed with protecting Xi. That's
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Hmm, post got messed up. Anyway the sentence was meant to read:
"The AC has such a hard-on for protecting the Chinese government that he has to complain about all the people calling out the PRC for inserthorriblethingthey'vedonetoday" (last word in brackets)
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You apparently love Xi, and are upset that anyone calls out him or his flunkies for any of the obviously horrific things they do in their own country. Never mind that nobody YET mentioned that here. YOU had to bring it up. And CO2 emissions? Why would you even bring up something like that? You aren't talking to Greta Thunberg.
You post like you're being paid to protect Xi.
Re: Dark matter is bullshit anyway (Score:5, Funny)
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If you have a better explanation why galaxies rotate much closer to being a solid disk than stars in orbit about the center (in which case the arms would be wispy thin with dozens of loops) please let us know.
Scientists know dark matter may not exist per se, but it is a reasonable inference given this observation.
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Intuitively, I would ask, "Why does a hill covered in mud hang there like a solid until it suddenly starts flowing when disturbed? Why does glass — arguably a highly viscous liquid — make great windows?" It's all about comparing the static forces that hold something together with the dynamic forces that cause entropy and having the former be greater than the latter, and when you're in the vacuum of space with relatively few particle interactions, even a tiny static force like microgravity from
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Apparently, the rotation of the galaxies is not a property of spacetime on large scales, it has to do with the structure of the galaxies itself, thus we have different behaviours between galaxies
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All the non-dark-matter explanations (light getting old, modified Newton Dynamics, TeVeS etc.pp.) hit a wall, whenever a new observation pops up.
You are referring to attempts to explain way dark matter -- that it does not really exist. What we are left with is the simplest conclusion - that dark matter is real we just don't know what it is. Physics has been at such a point many times before - with radioactivity, all manner of quantum phenomena before quantum theory, etc. This is what makes physics still very exciting, not just "the standard model describes everything, we are done".
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And we've also had giant hand-waves like "Oh, we can't explain why our measurements are a little bit off, so what if there are epicycles, and things orbiting around orbits around orbits around other things." Often when these hand waves occur, it's because there's something very fundamentally wrong with the assumptions [phys.org].
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I would agree with the notion that there is something fundamentally wrong with the assumptions, if it was single phenomenon that was off our calculations. But apparently, using Dark Matter as a gravitationally interacting but otherwise not observationable something which accounts for about four fifths of all mass in our Universe fixes more than just galactical rotation. It fixes gravitational lensing, it fixes the CMB
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What makes the 19 galaxies different from the others
Time, and the part of their life cycle we are currently observing them in. We like to think we've figured out how galaxies form and evolve, but with something that happens on such a huge scale of time it's impossible to do anything but speculate. Maybe we've got it all wrong, like Lamarck's idea of evolution... and maybe we'll never get it right. The human race simply won't be around for long enough.
Everybody onto the bandwagon to the dogpile! (Score:1)
Group every non-conformist with the nutjobs! Our conformist pseudoscience is best pseudoscience! Everybody who disagrees, must agree with some other pseudoscience! Hahaha! NOTHING in between! NOTHING! Kill all rational discussions!
-- You
Go back to Reddit, please.
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"I'm not that smart"
We know.
Those galaxies had their dark matter stolen by the Grinch.
He does that every year.
Dark matter....dark energy (Score:5, Insightful)
Re:Dark matter....dark energy (Score:4, Insightful)
Maybe in the end it was unwise to invent new physics to explain the incorrect astronomical predictions.
Especially now, when the new physics still leads to incorrect astronomical predictions.
Or maybe an explanation that makes sense (Score:2)
I love how you equate looking for answers that don't defy the laws of physics with "giving up".
I guess if you were taking a walk and noticed that one yard eas covered with see, while none of the neighbors were, you'd invent a new theory of gravity that causes all of the moisture to fall toward that one yard. The GP, on the other hand, would continue to investigate and think until he discovered that yard has sprinklers.
* covered with dew! (Score:2)
Argh. I REALLY need to start reading what autocorrect ended up with before hitting the submit button.
I type d-e-w and stupid phone changes it to "see".
Re: Dark matter....dark energy (Score:5, Insightful)
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If you "know" it is there merely because you fit the idea to the data, I dispute that you even have a hypothesis.
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The image [briankoberlein.com] shows a false-color representation of dark matter in six different galaxy clusters. Just as we can’t see infrared directly, but can detect it’s presence through CCD camera, we can detect dark matter by its gravitational effects on background light. The images are part of a recent work that analyzed the dark matter distribution in 72 colliding galaxy clusters. The results have further defined the n
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Not trying to flame you but there really isn't any gentle way to put this. Learn about something before you stupidly post on it.
Your first image is, the Crab Nebula in various wavelengths of light. Lets just pass that one as a mistake.
The second isn't false color imaging of dark matter. It's an image created by saying a matter distribution must be created by dark matter, fitting the data back to the hypothesis and saying dark matter should be here but we can't see it because it only interacts gravitationall
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It is one of the basic premises of philosophy that it is not provable.
You might just be imagining me.
That's why science sticks to falsifiable questions.
Re:Dark matter....dark energy (Score:5, Insightful)
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There is no experiment involved, merely observation of events from the distant past that can't be replicated, so physics didn't fail at all.
Astrophysicists failed to understand things distant, and they continue to fail to understand things at that scale. They just went from not even knowing, to being wrong about all the details.
Every new astronomical instrument that can see something new still uncovers stuff they didn't know. The only problem is, they already claimed to have answered everything!
If you compa
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1) No one ever claimed to have answered everything. That's not how science works.
2) Science does not require experiments. Science requires TESTABLE hypotheses.
Experiments are not required for a hypothesis to be testable. Making predictions that can be tested by new observations is the modus operandi for the scientific process. In astrophysics we get new observations to test the hypotheses all the time. Sometimes a hypothesis is wrong and must be adjusted or replaced, that's not something to be ashamed of. T
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Get back to me when the astrophysicists stop modelling galactic rotation using Newtonian mechanics. Until that time modeling galactic rotation using a known incomplete model of gravity and then claiming that it does not work and there must be the ether of matter fails Occam's razor. That and the fact there is something special about the local area in this galaxy so there is no dark matter despite it making up 2/3rds of the matter in the Universe.
It is my understanding that this is one of the things they wan
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Maybe in the end it was unwise to invent new physics to explain the incorrect astronomical predictions.
There are basically three possibilities. They are: 1) our observations are wrong, including the observations of 305 out of the 324 galaxies in this study . This is technically possible but wildly improbable given we have an absolutely enormous number of observations using dozens of telescopes analyzed by dozens of groups all arriving at the same conclusions. 2) Our known physics is complete and correct, but is being applied incorrectly to yield incorrect results. Given hundreds, maybe thousands, of very int
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Maybe in the end it was unwise to invent new physics to explain the incorrect astronomical predictions.
Especially now, when the new physics still leads to incorrect astronomical predictions.
Of course, there were the 305 other dwarf galaxies in this survey for which the dark matter hypothesis works just fine - read TFA. Something interesting is going on, probably with our (currently sketchy) models fo galaxy formation. But, dark matter being right out is not the leading candidate: otherwise, what's going on with the vast majority of galaxies? So far this has only shown up in looking at dwarf galaxies: so, the question could relate to "what makes dwarf galaxies dwarfy?"
Got a link for that star thing? (Score:2)
I haven't heard about it yet.
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Ignoring Space.com because it has some really shit anti-adblocking UI, I got the catalogue number "HD 140283" before the shit UI kicked in. I think the relevant paper is
available at https://arxiv.org/abs/1302.318... [arxiv.org]
The author's summary (not space.com, or whoever wrote the "popular" summary) states several relevant points immediately :
Proves, rather than disproves dark matter. (Score:5, Insightful)
This is not in fact as surprising or controversial as the press love to make out.
The original evidence that convinced many of us that what we called 'dark matter' was the 'Bullet nebula' in the Abell cluster, where the dark matter, as imaged by the red-shift of the galaxies behind it, did not follow the visible mass of two galaxies that had narrowly missed each other. Before that, all the errors we had seen were from galaxy rotations, and these could be explained as some fine tweak in the gravitational constant at galactic distances. But this showed the dark stuff could be 'flung' off when the visible matter is stopped by other visible matter. It is not surprising that galaxy formation may have the same irregularities in dark matter distribution. If you have a cloud of material that condenses onto two galaxies that fly apart, the dark matter may well not get split evenly. Probably buried in this data is some clue as to dark mater interaction, but we are not there yet.
On the other hand, if you don't want to believe in 'dark matter' as actual stuff, then how would you explain the two sorts of rotation they find in galaxies?
Dark matter must have some interactions with itself or it would not be clumped like this. We do not have any to study, but we can simulate some likely forms of self-interaction, and can model
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On the other hand, if you don't want to believe in 'dark matter' as actual stuff, then how would you explain the two sorts of rotation they find in galaxies?
Dark matter isn’t a binary variable. There isn’t an “on” and “off” state. None of the galaxies observed are fully stripped 100%, it is simply a continuous function. Functionally, the interactions play out as if a cloud of non-interacting (except through gravity) massive particles envelops the whole galaxy though it’s distribution remains a mystery.
Dark matter must have some interactions with itself or it would not be clumped like this. We do not have any to study, but we can simulate some likely forms of self-interaction, and can model
It is wrong to think dark matter must be self interacting [iop.org]. Although we don’t have enough evidence to say ei
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Dark matter isn’t a binary variable.
This is true. I was trying to keep the explanation short, and to match the original article. Now that people know to look for them, they have fund a number of galaxies that are 'light' in dark matter. I agree, it is unlikely that they have zero matter - just that some sort of slingshot process may have partitioned their matter differently. Presumably there are other galaxies with a double helping of dark matter.
Dark matter must have some interactions with itself or it would not be clumped like this. We do not have any to study, but we can simulate some likely forms of self-interaction, and can model
Ah. You got me on that one. This was a sentence that got lost off the bottom of my editor. I had
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Presumably there are other galaxies with a double helping of dark matter.
Yes, we have several candidates for such a thing "dark galaxies", not even counting the ultra-faint dwarfs [arxiv.org] that appear very common (based on our observations in the Local Group) and appear very likely to all be dark matter concentrations with very little baryonic matter.
The truth of the matter is that evidence for the reality and ubiquity of dark matter is piling up very fast. There is no credible basis for dismissing its reality. There will be some hold-outs of course among real scientists, as there always
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Astronomers Find 19 More Galaxies Missing Their Dark Matter
Nobody leaves the room! And Jones, if I find out it was you again, there'll be a parent-teacher meeting in short order.
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Well at leas the Methuselah star doesn't *necessarily* show a discrepency with the age of the universe (while the age is older, it is '+/-' 800 Million of error, which means it doesn't confidently conflict with the other measurement.
The point still stands that we have a lot of missing knowledge and best-guess stand-ins to fill gaps, but currently the star does not necessarily present an indiscrepancy in and of itself.
Dark Energy, Dark Matter (Score:2, Interesting)
Re:Dark Energy, Dark Matter (Score:5, Informative)
By fitting a theoretical model of the composition of the universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~68% dark energy, ~27% dark matter, ~5% normal matter. What is dark matter?
We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.
However, at this point, there are still a few dark matter possibilities that are viable. Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements. These possibilities are known as massive compact halo objects, or "MACHOs". But the most common view is that dark matter is not baryonic at all, but that it is made up of other, more exotic particles like axions or WIMPS (Weakly Interacting Massive Particles). https://science.nasa.gov/astro... [nasa.gov]
Re: Dark Energy, Dark Matter (Score:5, Informative)
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... and the observational searches for MACHOS carried out over the last 35-odd years (that I've been watching, anyway) really aren't coming up with enough such matter to balance the cosmological books. They are there, but not enough of them.
Sure, the galaxy-formation theories need changing. (Score:5, Interesting)
The galaxy-formation theories are all about a step and a half up from wild-ass guesses. The current galaxy-formation theories failing to stand up to new observations is about as surprising as a snowstorm in Michigan in January.
The important thing is, these cases of missing dark matter make it all the more certain that the cause of the observations that led to the dark matter hypothesis is indeed a matter of a real form of matter that makes up part of the composition of most galaxies.
If the problem with our observations was that General Relativity was wrong at large scales, that the real law of gravity was different, then every galaxy without fail would follow the different gravitational law, and thus they would all move the same way. If a small minority of galaxies move differently, though, that tells you that the issue is a difficult-to-observe factor in the composition of galaxies.
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Why assume it's matter that's warping spacetime?
Nobody that actually knows Relativity assumes this.
GM states that *energy* warps spacetime, including condensed forms of it such as matter.
Heck, warped spacetime contains energy, so it even warps itself (which will warp itself even more and so on, to a limit).
And this kind of non-linear behavior is exactly what makes GM warping so difficult to calculate.
Simplest explanation.. (Score:5, Funny)
Re:Simplest explanation.. (Score:5, Funny)
Or, it could just be that there are no tasty animals there for Nibblonians to eat.
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Humans taste bitter, so they might start mining our dark matter also. Although, if you soak us in vinegar...
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Dark Matter = Gasoline? (Score:2)
Could it be missing because it was used as a fuel source?
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Re: And in the end, they'll find out ... (Score:3)
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Dark matter is for wimps (Score:1)
Galaxy: "Dark matter? We ain't need no stinkin' dark matter!"
Not just 19 galaxies ... (Score:2)
stop calling it dark matter (Score:2)
Call it for what is experimentally observed: blahblahblah discrepancy.