Astronomers Detect Extended Dark Matter Halo Around Ancient Dwarf Galaxy (phys.org) 48
fahrbot-bot shares a report from Phys.Org: The Milky Way is surrounded by dozens of dwarf galaxies that are thought to be relics of the very first galaxies in the universe. Among the most primitive of these galactic fossils is Tucana II -- an ultrafaint dwarf galaxy that is about 163,000 light years, from Earth. MIT astrophysicists have detected stars at the edge of Tucana II, in a configuration that is surprisingly far from its center but nevertheless caught up in the tiny galaxy's gravitational pull. This is the first evidence that Tucana II hosts an extended dark matter halo -- a region of gravitationally bound matter that the researchers calculated to be three to five times more massive than scientists had estimated. This discovery of far-flung stars in an ancient dwarf galaxy implies that the very first galaxies in the universe were also likely extended and more massive than previously thought.
The team used an imaging filter on the telescope to spot primitive, metal-poor stars beyond the galaxy's core. Analysis shows a kinematic connection, that these far-out stars move in lockstep with the inner stars, like bathwater going down the drain. The results suggest that Tucana II must have an extended dark matter halo that is three to five times more massive than previously thought, in order for it to keep a gravitational hold on these far-off stars. "Without dark matter, galaxies would just fly apart," Chiti. says. "[Dark matter] is a crucial ingredient in making a galaxy and holding it together." The team's results are the first evidence that an ultrafaint dwarf galaxy can harbor an extended dark matter halo. "This probably also means that the earliest galaxies formed in much larger dark matter halos than previously thought," The findings appear in the journal Nature Astronomy.
The team used an imaging filter on the telescope to spot primitive, metal-poor stars beyond the galaxy's core. Analysis shows a kinematic connection, that these far-out stars move in lockstep with the inner stars, like bathwater going down the drain. The results suggest that Tucana II must have an extended dark matter halo that is three to five times more massive than previously thought, in order for it to keep a gravitational hold on these far-off stars. "Without dark matter, galaxies would just fly apart," Chiti. says. "[Dark matter] is a crucial ingredient in making a galaxy and holding it together." The team's results are the first evidence that an ultrafaint dwarf galaxy can harbor an extended dark matter halo. "This probably also means that the earliest galaxies formed in much larger dark matter halos than previously thought," The findings appear in the journal Nature Astronomy.
Wait (Score:2)
Didn't we say there was no dark matter only a few short days ago?
Re:Wait (Score:5, Informative)
2 parts:
* We know some forms of dark matter exists and have been tested. The idea that there's mass that doesn't interact with the electromagnetic spectrum is validated by neutrinos and we've been measuring them since the 1940's. They just don't have all of the same physical attributes that explain the astronomical observations. Mostly the issue with neutrinos is they're extremely light and fast objects and we expect them to represent only a small percentage of the mass in the Universe. We don't have a known particle with a lot of mass, that we think could have formed early on near the Big Bang, and which has the appropriate expected velocity.
* The articles about theories like Modified Newtonian Dynamics (MOND) are generally indications that a prediction from those theories wasn't falsified. That doesn't mean they're right, just that they were successful at extrapolating a collection of observations that were predicted to a new situation. That's the same standard that Dark Matter has been facing since the idea was proposed 50 years ago when it was initially used to explain just abnormal orbital velocities of stars to now where evidence for it can be seen as far back as the Cosmic Microwave Background indicating something existed even back 13 billion years ago with at least some of the expected properties of mass with no electromagnetic interaction.
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From the introduction to that paper:
The existence of DM is a key assumption of the standard cosmological model cold dark matter (CDM), which has been successful in explaining many cosmological observations on the largest scales of the cosmos (Frenk & White 2012; Peebles 2012). The CDM paradigm, however, is facing several challenges on small scales (Kroupa 2015; Bullock & Boylan-Kolchin 2017)
So they acknowledge that DM works well in the Universe as a whole, but are claiming only modifications in gravity theory may be needed at certain small scales. And, BTW, observations in the local small scale (the Local Group) and the Milky Way galaxy itself stribgly supports DM and - literally a few days ago (two to be exact) evidence was published for DM on an even smaller scale, a dwarf galaxy.
Hints and indications - no DM discoveries (Score:2)
Seems like this boils down to "we have considerable indirect evidence there is additional mass, but we can't find it."
We're all looking forward to them, you know, finding it so we can all learn WTF that mass is, or, what else is going on that makes it look like there is unfindable mass.
I have yet to run into anything that adds anything useful to that.
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Seems like this boils down to "we have considerable indirect evidence there is additional mass, but we can't find it."
This line of logic blows my mind.
Indirect evidence? What would direct evidence be for you?
I'm pretty sure by your bar, we have only indirect evidence of nuclear fission.
As for the mass- they've absolutely found it. We can, as you've noted, observe and quantify its effects.
What we can't say, is what the fuck the stuff is, with respect to the standard model of particle physics.
Which really shouldn't be so troubling; because we haven't been so troubled by other pitfalls in the standard model.
Today, neut
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A test tube... or cloud chamber... or box... or E/M/EM field... refrigerator... containing, or radiating, or generating, or devolving/evolving into, you know, dark matter.
I'm pretty sure you're bewildered about dark matter as compared to nuclear fusion. The latter, to be clear, we can produce in a garage, a tokamak, via LASER compression, make fusion bombs, etc. We know what it is, we know h
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Re:Astronomers talk about primitive dwarf galaxies (Score:4, Funny)
We asked the galaxies about their preferred pronouns and such, but there's been no word yet.
(Earth) "Could you please tell us your preferred pronoun? We don't want to offe..."
* Galaxy emits massive burst of radiation towards Earth, killing everything *
(Galaxy) "You're welcome, Universe."
Re: Astronomers talk about primitive dwarf galaxie (Score:2, Insightful)
1984 Newspeak alive and well right now:
Self-proclaimed anti-racists tell us race is the critical factor in pretty much everything from how we look at history to who should get jobs, covid vaccines, educational assistance, tax dollars, treated by criminal justice system, etc.
Racists are people who think race should not be a deciding factor but facts, merit, individual need, capability should drive these decisions on an individual basis.
Anti-racists say these things non-ironically and attack, cancel and activ
In otherwords, thru the looking glass back in time (Score:2)
This expanding universe we perceive is simply the BFBH that surrounds all the stars, galaxies and planetary systems.
Potentially Silly Questions (Score:4, Interesting)
I'm interested in understanding the way that we rationalize the existence of Dark Matter and Dark Energy. In particular, my limited understanding is that these theoretical properties of the universe are essentially deduced through an application of Occam's Razor: we have no concrete evidence of the existence of either, but there is an argument to be made that suggests that these are the simplest explanations for the observable universe. This may not be 100% correct, but I hope I'm close enough...
There are a couple of aspects of this which I find fascinating.
The first concerns the relationship between Dark Matter and/or Dark Energy and the Standard Model. We know that neither DM nor DE feature in the classical Standard Model, although we do have less well established theories such as supersymmetry which may have a way to explain both without breaking what has become relatively well established as the prevailing model of our universe.
But before we get to DM and DE, let's take a moment to think about our current Standard Model and the inclusion of gravity. At the moment, we consider that the force of gravity is created between matter through some form of exchange or transfer of theoretical tensor bosons we've called gravitons. OK. But we also know (for example from the recent and amazing results from the LIGO experiments) that our spacetime can be warped (distorted) by certain ultra-high energy events such as the collision of two black holes.
So my first question is: what if the graviton doesn't exist at all... because gravity isn't a force; rather it is a property of our spacetime? What if gravity is "what you get when what we currently consider to be matter interacts with what we currently understand to be spacetime?" [ Matter influences spacetime >> spacetime distorts >> distortion of spacetime gives rise the the observable effect we call gravity]?
You can already tell I'm not an astrophysicist, right? Thought so. The reason I wanted to bring this aspect of our current universal model forward first, is that if there is even a tiny possibility that gravity can be some form of consequence or universal property, rather than a force, then it follows [to my non-astrophysical mind] that maybe the same could be true for dark matter.
Now, for this crackpot, ignorant, hare-brained theory to be close to relevant to the topic at hand, we might be able to consider that there is something else interacting with spacetime that is causing the distortion of spacetime that in turn gives the impression of matter. Put another way, if we start from the premise that the only thing that can "cause" the force of gravity to exist is some form of matter, then that's what we'll start to look for. On the other hand, if we're willing to consider that gravity is a property of our spacetime rather than a force [which might explain why we haven't found a force particle for it yet] then we open the cognitive door to the idea that maybe there are other phenomena that can interact with our spacetime in a way that gives a result that looks to us like gravity.
I have a really terrible, awful visualisation that helps me think about this... Remember all those high school models of gravity we saw done with a large sheet of rubber" [youtube.com]? What if that rubber sheet was a representation of our spacetime and the metal bearings being placed on it were conventional matter as we understand it. But now visualize what would happen if I ducked under that table with a powerful magnet and started to influence the motion of the metal bearings, say by placing the magnet directly adjacent to the central mass.
In my hypothetical model, we would observe that the behavior of the bearing would deviate from our mathematical models and we would infer that there was "some invisible force" acting on it.
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This has also interested me from the moment I first read about the observations.
But rather than think about this as a "less crazy" hypothesis, doesn't the idea of "space itself expanding" line up with the mathematic
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Oh, sorry, but you are somewhat confused.
You can have faster than c expansion between two (distant) points even in a universe that does not undergo acceleration of its expansion. Just look how slow the expansion is over some small distance, and then take distance that times bigger than the local expansion is lesser than c. That simple it is.
The acceleration of expansion (and dark energy) is about something different.
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Space can expand even without dark energy, because it has some impetus since its very onset. Dark energy makes that expansion of space getting accelerated. But may be we just have issues to understand each other when communicating this remote way. :-)
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Space can expand even without dark energy, because it has some impetus since its very onset
This would be quite the statement, but no less than our current situation. In my internet-forum armchair education, change requires an energy gradient. And there is no precedent, yet, of a macro-scale event occurring that doesn't require energy. Space expanding without "energy" of some sort, would be a first of its kind. To say that something just "naturally does something" has generally been the way of pre-science philosophy, and "dark energy" is the place holder for what ever the fk is causing space to ex
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Well, there are two different points to it:
The expansion started with big bang, and current theories stumble with finding reasons (incl. some form of energy, the inflaton) for its occurrence. Regardless of the reasons of its occurrence, it provided the Universe with some impetus (it is not the official label for it), meaning it got a big expansion speed.
Then you do not need to continuously add some another impetus for it to continue its expansion (alike it is enough to hit an object to have some speed for s
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we do have believe reality to be real.
Well sure we don't, not really; we only have to behave within the constraints we (think we can) observe.
But... so far what we perceive as reality has resisted any of our attempts to prove or disprove it, so believing reality is real is the longer path to madness, at least for now.
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I'm interested in understanding the way that we rationalize the existence of Dark Matter and Dark Energy.
Decades of evidence says there is matter that exists that does does not react like ordinary baryonic matter other than it has gravity. Decades of evidence says that the universe is expanding faster than gravity of all matter dark or baryonic should allow. It is not rationalization as much as reluctant acceptance that there is unknown matter and energy.
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Hi, I do not know if I understand you, but if yes, you got it wrong:
Observations (Score:1)
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Plentiful consequences of both special and general theory of relativity were detected. It is the way how you prove a theory, that is you detect what it says you should detect.
PS I do not argue on the so called conspiracy theories, I simply inform on science.
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Einstein's Relativity is the most proven theory in the existence of science.
We're more confident that relativity exists than we are your higher level functions aren't being conducted by pan-dimensional hyper-intelligent mice.
Well, except for the evidence that you're woefully ignorant.
I think everybody needs to remember that THEORY means that which we believe to be true but is not yet proven.
And I think you need to work on your education before trying to talk w
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But before we get to DM and DE, let's take a moment to think about our current Standard Model and the inclusion of gravity. At the moment, we consider that the force of gravity is created between matter through some form of exchange or transfer of theoretical tensor bosons we've called gravitons.
Actually, we don't. The current model for gravity is general relativity (GR). Gravity in GR is not quantized: it is exchanged in continuous waves and fields, not discrete particles. The "graviton" is a purely theoretical particle featured in possible theories of a quantum gravity. However, these theories are all very hypothetical, and there is basically no evidence for any of them. In fact that means you're kind of right: gravity in the Standard Model (SM) isn't a force, but just a property of spacetime.
Now, for this crackpot, ignorant, hare-brained theory to be close to relevant to the topic at hand, we might be able to consider that there is something else interacting with spacetime that is causing the distortion of spacetime that in turn gives the impression of matter. Put another way, if we start from the premise that the only thing that can "cause" the force of gravity to exist is some form of matter, then that's what we'll start to look for. On the other hand, if we're willing to consider that gravity is a property of our spacetime rather than a force [which might explain why we haven't found a force particle for it yet] then we open the cognitive door to the idea that maybe there are other phenomena that can interact with our spacetime in a way that gives a result that looks to us like gravity.
Th
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As the following will clearly demonstrate, I'm no astrophysicist. I'm no kind of physicist. But I'm fascinated...
Apparently not fascinated enough to bother looking at the Wikipedia page on the subject [wikipedia.org].
Seriously - read the page. It details eleven different types of evidence that provide overwhelming evidence for the make the real existence of Dark Matter.
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From the page you claim offers "eleven different types of evidence that provide overwhelming evidence for the make[sic] real existence of Dark Matter"
"Because dark matter has not yet been observed directly, if it exists, it must barely interact with ordinary baryonic matter and radiation, except through gravity."
So to summarize, the source you cite as containing elev
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So my first question is: what if the graviton doesn't exist at all... because gravity isn't a force; rather it is a property of our spacetime? What if gravity is "what you get when what we currently consider to be matter interacts with what we currently understand to be spacetime?" [ Matter influences spacetime >> spacetime distorts >> distortion of spacetime gives rise the the observable effect we call gravity]?
That's called the Theory of General Relativity.
There is lots of evidence for gravitation being a fictional force, not a real one. There is no evidence for the graviton- so I'd consider the former the prevailing view.
Fortran code on GitHub (Score:4, Interesting)
What the summary does not mention is that the Nature article [nature.com] has a link to their code on GitHub [github.com]! The authors are distributing on GitHub a version of Professor Chris Sneden (U Texas at Austin)'s MOOG stellar analysis code [utexas.edu] including a patch by Jennifer Sobeck (Washington University) so that it can handle low metal stars. It appears to be an example of scientists using open code and enhancing it over time which is awesome.
The code is in Fortran, which maybe most people haven't seen before so that's interesting too. (I was introduced to it briefly and typed it onto punch cards (hollerith cards) in a Saturday classes at a high school when I was a little kid.) It explains how to build it with the g77 Fortran compiler too. Yes a big regional high school in the 70s had a mini-computer hardware suite that took up a small room including standalone machines like keypunch stations, card reading hoppers, and output stations. The room sized ensemble had magnitudes (Maybe 1,000 to 10,000 [deviceplus.com]?) less power than a Raspberry Pi.
Wonders of the Universe (Score:3)
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Given enough time, and assuming we don't obliterate ourselves before it happens, I would imagine we'll either invent a way to upload our consciousness into machines, or invent some form of "living machines." Either of which will be capable of being used to overcome our biggest obstacle today when it comes to exploration away from our shiny blue ball: time. Once we're capable of continued "life" for the thousands of years it would take to travel those distances, I would think it would be inevitable that so
*sigh* Another poorly-written science headline (Score:2)
Astronomers Suspect Extended Theoretical Dark Matter Halo Around Ancient Dwarf Galaxy
There, fixed that for you.
No wonder so many brainlets in this country don't trust science.
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Fringe... (Score:2)
This shit is all at the fringe of our knowledge as evidenced by the constant back and forth. And not saying that makes anyone stupid or wrong, that's how science works of course. However it gives rise to this strange phenomenon where people start imbuing (awed ooooh) "Dark Matter" with all kinds of special magical thinking because it sounds super mysterious and frankly despite all the majesty and unknowns of the universe really it's all pretty clockwork and boring when you boil it right down.
So they should
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So they should have called it something like "rounding error matter" or "model flaw matter" or something, because that's all that shit is.
No, it's not.
Perhaps a better name for it would have been Weakly Interacting Massive Particles, which is the predominant hypothesis for what the shit is.
The idea that DM is some kind of magical fictional rounding error is nonsensical. A dumb fucking urban legend spread amonst morons who think they know something. If I had a penny for every time some dumb fuck who fancies themselves smart tried to pitch that dumb shit to me...
It started life as that- but then we fucking found it. We take pictures of it