from the noone-knows-how-the-cloud-works dept.
A nearly invisible dwarf galaxy is challenging the model of dark matter. An international team of astronomers, led by the Instituto de Astrofísica de Canarias (IAC) in collaboration with the University of La Laguna (ULL) and other institutions, discovered this fascinating galaxy dubbed "Nube."
Nube, which means "Cloud" in Spanish, was named by the 5-year-old daughter of one of the researchers, aptly reflecting the galaxy's ghostly and diffuse appearance. Its discovery is significant because its faint surface brightness allowed it to remain undetected in previous sky surveys, despite its considerable size.
"With our present knowledge we do not understand how a galaxy with such extreme characteristics can exist," says study first author Mireia Montes, researcher at the IAC and the ULL, in a media release.
Nube is unique in its properties, being ten times fainter yet ten times more extended than other dwarf galaxies with a similar number of stars. Its discovery is akin to finding a hidden treasure in a well-explored attic. Nube is large and yet faint, a ghostly apparition in the universe. To put it into perspective, it's about one-third the size of the Milky Way but has a mass comparable to the Small Magellanic Cloud.
What sets it apart is its significant amount of dark matter, an invisible substance that does not emit, absorb, or reflect light, making it undetectable by traditional telescopes.
Related: Bizarre Galaxy Discovered With Seemingly No Stars Whatsoever
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Bizarre Galaxy Discovered With Seemingly No Stars Whatsoever:
A newly discovered object is stretching our understanding of what constitutes a galaxy.
Called J0613+52, this massive blob of something some 270 million light-years away appears to have no stars whatsoever. At least, none that can be seen. It's just a haze made of the kind of gas that's found between stars in normal galaxies, drifting around by its lone self like an absolute badass.
Its mass and motion appear to be normal for what we'd expect of a spiral galaxy... in fact, if you extracted the stars from a spiral galaxy like the Milky Way or Andromeda, J0613+52 is pretty much what you'd end up with.
According to a team of astronomers led by astrophysicist Karen O'Neil of the Green Bank Observatory, it could be the first discovery of a primordial galaxy in the nearby Universe – a galaxy made up mostly of the gas that formed at the beginning of time.
(Score: 2) by looorg on Wednesday January 31 2024, @10:21AM (1 child)
I'm surprised they have not changed the name "dwarf" galaxy into something less offensive yet. Midget galaxy? Tiny Galaxy? Less then average size galaxy?
(Score: 0) by Anonymous Coward on Wednesday January 31 2024, @10:00PM
"Galaxy Of Restricted Growth", because gorg is less offensive than dwarf.
(Score: 3, Touché) by Gaaark on Wednesday January 31 2024, @11:58AM (28 children)
Finally some science is entering physics: hopefully some common sense as well.
Dark. matter. does. not. exist.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 1) by khallow on Wednesday January 31 2024, @01:45PM (10 children)
Unless, of course, it does and this galaxy happens to have an unusually large amount of it relative to its visible matter. Remember we do have various sorts of dark matter presently (as you know, we ourselves are dark matter due to our low EM emissions per unit mass), we just don't yet know of enough of it to explain our observations.
I find it interesting, for example, how cold neutrinos (that is, neutrinos moving at slow interstellar speeds) still haven't been ruled out - aside from figuring how where they would come from. If there is a mechanism [sciencedirect.com] for creating enough of them, then that would explain things quite well. And they would be incredibly difficult to detect since they would have many orders of magnitude less energy than solar and human-generated neutrinos.
(Score: 4, Informative) by Immerman on Thursday February 01 2024, @05:22PM (9 children)
Again with this "we are made of dark matter" B.S.
The "Dark" in dark matter doesn't mean non-luminous, it means undiscovered. Like how Africa was once known as "The Dark Continent" - they never meant the sun didn't shine there.
Way back when it was first proposed, yes, dark matter could have just been undiscovered non-luminous matter like rocks, gas, etc. In fact that was the general assumption until we went to look for it.
Not anymore - we've searched for and ruled out almost all possible normal-matter candidates for dark matter - aside from being a huge number of black holes within an implausibly narrow range of sizes.
If it's not that, and it actually exists rather than just being an artifact of an imperfect understanding of gravity, then it's has to be something that not only doesn't emit light, but doesn't interact with it at all. Enough rocks, planets, etc. would obscure distant starlight, revealing its existence. We see no evidence of that. Enough gas would would absorb certain wavelengths of light passing through it, imprinting its absorption spectra over what was coming from the stars themselves. We see no evidence of that..
We're talking about the galaxy being embedded in a cloud of 5x more mass than all the stars combined. It could have hidden from the telescopes when the theory was first proposed, especially since nobody was looking for it. But our telescopes have gotten better, and we've been searching for any hint of evidence for anything that it could be. Whatever it is - light doesn't interact with it.
Which, yes, leaves cold neutrinos as a possibility, since light doesn't interact with them either. But you would have to explain both why none of our neutrino detectors are showing background neutrino levels levels radically higher than what we can detect coming from the sun, nuclear reactors, etc. As well as where they came from, since there's no known mechanism to explain how they could have cooled down rapidly enough from when they were in thermal equilibrium with the dense, hot, early universe, which would have required them to have relativistic velocities. And hot neutrinos couldn't have contributed to the early structure formation in the universe, which is one of the major arguments supporting the existence of dark matter.
So basically - if it is cold neutrinos, you've just replaced one mystery with an even bigger one. Which doesn't mean it's not true... but it's not super promising either.
What would be more promising is if we were to discover neutrinos actually do have radically more massive antiparticles that also don't interact with light. Those would be a prime Dark Matter candidate, as well as simultaneously solving the mystery of how neutrinos can have mass at all (and are thus able to oscillate between flavors) - since they need to have an antiparticle in order to couple with the Higgs Field and get mass the same way other fundamental particles do.
Science has a long history of big advances in our understanding answering multiple seemingly independent questions simultaneously. Like Relativity - which simultaneously fixed the problem of Maxwell's Equations predicting completely different electromagnetic forces based on your reference frame, explained the anomaly in Mercury's perihelion precession, and several others.
(Score: 1) by khallow on Thursday February 01 2024, @09:37PM (8 children)
Except it does mean non-luminous matter. Enough non-luminous matter of any sort moving at slow enough velocities in the places where it needs to be to explain observation.
Doubtful. We already have a huge unknown in the beginnings of the universe. This would illuminate that. At some point the universe would become transparent to neutrinos (possibly in a sufficiently gradual way that forces the neutrino fluid to match velocity), that's probably the earliest we can possibly observe via primordial subatomic particles unless there's something that interacts even less.
(Score: 2) by Immerman on Friday February 02 2024, @02:51PM (7 children)
Except we've looked where it needs to be, and can see nothing. And we've looked carefully enough that if it were gas, rocks, or almost anything else that interacted with photons, we'd have seen evidence of it. You'd basically need sufficiently small black holes, or maybe neutronium chunks, to get enough mass in the right places without the bits being large enough to be noticeable against the backlighting from other galaxies.
We also have a huge known in the moderately early universe, the CMBR, which tells us that the temperature was extremely hot and uniform ~13.5 billion years ago, which sets the temperature of the neutrinos as well - since even with their low interaction rate the preceding 370,000 years would have given them plenty of time to reach equilibrium with everything else. Which given their infinitesimal mass would mean relativistic velocities.
And the universe would always have been almost completely transparent to neutrinos, except maybe in the first few moments before quarks cooled enough to form protons and neutrons - assuming that actually happened (before the CMBR our knowledge gets increasingly uncertain). Only interacting via the weak force and gravity means that even stars and planets are almost completely transparent to neutrinos, they wouldn't really care about the plasma that made the early universe opaque to photons. Even a light year of solid lead would only stop about half of them.
(Score: 1) by khallow on Friday February 02 2024, @04:16PM (3 children)
Except? That would be non-luminous matter in a nutshell. You have to look indirectly. I understand gravitational lensing shows something is going on.
(Score: 2) by Immerman on Friday February 02 2024, @05:04PM (2 children)
Look at your hand - it's non-lumnous matter, yet you can still see it.
Pitch black night so you can't actually see your hand directly? Hold it up to the stars, and you can still see its outline by the stars that it obscures. And that's true of ALL luminous matter. Even glass is completely opaque across much of the EM spectrum.
And yet when we look at where we know dark matter must be, we see neither. So we know whatever is there (if there's really something there), it doesn't interact with light. Which rules out anything made of atoms.
(Score: 2) by Immerman on Friday February 02 2024, @05:17PM
Sorry, that should be:
And that's true of ALL normal matter.
not luminous
(Score: 1) by khallow on Saturday February 03 2024, @06:15AM
Only because it's near my face. If it were 50k light-years away at the edge of the Milky Way, I wouldn't see it that way, even if there were several million solar mass of them out there. At that point, you'd have to look for indirect effects like occultation or gravitational lensing.
The problem then is that a dense object like a hand doesn't occult much for its mass. Nebula are extremely puffy - Wikipedia states a typical nebula cloud the size of Earth would weigh a few kilograms. That's a few hands of mass. And illuminate that nebula with ionizing uv or x-rays and suddenly you have an object much brighter than its equivalent in hands would be.
We do see gravitational lensing.
(Score: 1) by khallow on Friday February 02 2024, @04:24PM (2 children)
This. Except in the first few moments. We don't have an understanding of the earliest moments of the universe, but it keeps getting hotter and denser.
(Score: 2) by Immerman on Friday February 02 2024, @05:07PM (1 child)
Right, so any neutrinos that existed at that time would be hot, and matter has been two diffuse since the CMBR for them to shed much of that heat.
(Score: 1) by khallow on Saturday February 03 2024, @06:29AM
Unless, of course, that velocity was shed. The paper I linked back some ways had a mechanism - interaction with strong magnetic fields.
And there would be additional velocity loss from red shift. For example, from the most distant galaxies, one gets red shifts of over 10. What that means is that light traveling from that galaxy loses a factor of ten or more energy in its travel to us. A typical near light-speed neutrino taking the same route would lose a similar amount of energy. Neutrinos from the initial moments of the Big Bang would lose much more energy due to much higher red shifts - we're talking orders of magnitude loss. If they start with initial extremely high energy, then they can stay hot and extremely fast even now. But if they don't, then they can well slow down enough by now that they can be caught by galaxies.
That's the theoretical mechanism for cold neutrino creation and capture.
(Score: 2) by hendrikboom on Wednesday January 31 2024, @06:52PM (7 children)
We know something exists, and we call it dark matter.
For all we know, though, it may not be matter at all,
but something not yet dreamed of.
(Score: 4, Insightful) by Gaaark on Wednesday January 31 2024, @10:10PM (6 children)
Teh problem is we DON'T know 'something exists': they just say something must exist if General Relativity is correct.
If GR is NOT correct, then that 'something exists' does not need to exist.
I just believe that there is something wrong with our current physics and we need to rethink it, not just say GR cannot be wrong so let's invent 'Dark Matter'.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 2) by Immerman on Thursday February 01 2024, @05:46PM (2 children)
It's a valid argument - the problem with it is that we've been testing GR in every way we can think of, trying to find any flaw in it, since pretty much the day Einstein first published it. And it has passed *every* test we've thrown at it with flying colors. Even the really ridiculous "okay, there's _no_ way this could be true" predictions have consistently been validated.
Until we get to near-galactic scales - then weird things start happening. But we have no way to do experiments at that scale to actually test things and get to the heart of the problem directly.
Meanwhile, we're still waiting for anyone to come up with any other theory of gravity whose predictions match observations half that well. So far nobody has even come close. Some of the MOND theories are improving rapidly - but they've been doing so for decades and still don't hold a candle to GR.
But the search for alternative theories of gravity is going strong - and getting stronger with every year we fail to find any direct evidence of dark matter. There's just not a lot of big money or headlines in that search because you don't need any big expensive equipment to come up with a theory and, well, so far everyone has failed. Not exactly big headlines. In physics circles huge numbers of people trying and failing to come up with alternative theories that work as well as the widely accepted ones is kind of the whole point of the profession. Nobody is going to take you seriously until you've actually got something to show for your efforts.
Meanwhile, a big expensive experiment designed to find some evidence of Dark Matter Candidate X is at least news - if there wasn't fairly widespread belief that it was at least a credible candidate, the experiment never would have gotten funded in the first place
(Score: 2) by Gaaark on Thursday February 01 2024, @09:33PM (1 child)
Newton's theory of gravity was good for a long time and still holds for a lot of things... but was wrong.
GR holds for a lot of things but cannot be married with the quantum world, and therefore is wrong.
Quantum Inertia:
has DARPA funding and was satellite launched... just waiting for it to be activated to see results.
https://physicsfromtheedge.blogspot.com/ [blogspot.com]
Not married to it completely, but it's nice to see an actual formula (without modifications like MOND) that has worked again and again.
Works with the quantum world and seems to work just like GR but without all the GR problems.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 2) by Immerman on Friday February 02 2024, @03:09PM
Or QM is wrong. Both theories are extremely well tested, and both have some major mysteries hinting that they are incomplete. For QM the biggest mystery is "What is a measurement?" - nothing in the theory even hints at an explanation as to why quantum wavefunctions should ever collapse.
It could very well be that GR is correct, while our current QM theories are just an oversimplification based on the incorrect assumption that spacetime is flat. The math for QM in curved spacetime would likely be atrociously complicated - but that isn't actually an argument against it.
As for the QI, etc. stuff - you shouldn't give it too much credence just because the NASA "fringe science division" is investigating them. They're basically the debunking team, their whole shtick is testing ideas that are almost certainly garbage, but whose benefits if they somehow actually worked would be so great that it's worth making *sure* of that before throwing them away.
(Score: 2) by hendrikboom on Thursday February 01 2024, @06:05PM (2 children)
Maybe all that exists is a different theory of gravity, still to be discovered.
(Score: 2) by Gaaark on Thursday February 01 2024, @09:14PM (1 child)
Yup!
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 2) by Unixnut on Thursday February 01 2024, @10:50PM
Well, one hypothesis is "Variable Gravity" from what I remember of the subject. Namely that just like Newtons laws break down at the extremes, so may our model on how gravity is supposed to work.
After all, most of our study of gravity has been local to our planet. Only relatively recently in human scientific study have we got the tools to observe gravity at its extremes (black holes and entire galaxies), and there we find our model breaks down. Dark matter is one of those things added to make our current models carry on working.
I'm no expert myself, but a quick search online sees that there is a lively debate on the matter:
https://en.wikipedia.org/wiki/Modified_models_of_gravity [wikipedia.org]
https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics [wikipedia.org]
https://physics.stackexchange.com/questions/319575/dark-matter-vs-modified-gravity [stackexchange.com]
(Score: 2, Interesting) by shrewdsheep on Wednesday January 31 2024, @08:47PM (8 children)
This galaxy may actually be proof of the existence of dark matter. If there is invisible mass in the galaxy and dust can be excluded convincingly, well there you go. There is something that is not elsewhere.
Many years ago I got tricked by a documentary wherein scientists showed an animation indicating positions of dark matter. I thought that they had actually identified those positions, which would have counted as proof for me. Later I learned that these were just simulations, which of course proof nothing. Since then I became very skeptical of dark matter and went with those saying we merely have to modify our laws of nature. Actually, it does not make a difference whether we modify our laws or assume an invisible matter. The invisible matter would be how we modify our laws. A meaningful distinction though, which could settle the matter is to decide whether this dark matter that is so much talked about is homogeneously distributed or not.
(Score: 5, Insightful) by Immerman on Thursday February 01 2024, @06:08PM (7 children)
The problem is that science doesn't deal in proof. It's logically impossible to prove *anything* conclusively - the real answer could always be "Because God wills it so", and all our physics, etc. is just an overly complicated fantasy that happens to fit the data They have revealed so far.
Even in mathematics, a field build entirely on rigorous logical proofs, every proof boils down to "If W, X, and Y are true, then Z must also be true". You can never prove that Z is true, because if you trace the foundations of W, X, and Y, you will always eventually reach A, B, and C, which are just "obviously true" assumptions that are accepted as being true without any proof (a.k.a. "axioms"). In fact it's been rigorously proven that it's impossible for any logical system to prove its own validity.
In this case "If there is invisible mass in the galaxy" also makes the implicit assumption "And GR is correct". Because the failure of GR's predictions is the only evidence we have that there is any invisible mass.
And one of the fundamental assumptions at the root of all of science is that the rules we know are wrong. Every law of physics is presumed to only be an imperfect approximations of reality that will eventually be improved upon - because that's what has always happened so far. Even if some really are perfectly correct, it will be impossible to ever know that for sure. Either science continues improving our understanding forever, or eventually we reach the point where there are no more outstanding mysteries and we give up on ever learning anything more, accepting whatever "really-good approximations" we have as being as good as we'll ever get, because we don't have any more mysteries to point us at better ones.
(Score: 2) by Immerman on Thursday February 01 2024, @06:10PM
Oops, realized as I clicked submit that I mangled first paragraph. Should start:
The problem is that science doesn't deal in proof, it deals in the preponderance of evidence.
(Score: 1) by khallow on Thursday February 01 2024, @10:00PM (5 children)
The logical system has to be sufficiently complex. For example, in the empty logical system there's nothing to prove and hence, validity is trivial. In a simple system of axioms without implication, you have a similar situation - such as "A is true." The only logical statements in the system are Boolean expressions of the finite axioms. And thus, the system is provably valid.
Once your system is complex enough to include a representation of the natural numbers, then you can't prove the system of logic is valid. This is a sufficient not necessary condition.
(Score: 2) by Immerman on Friday February 02 2024, @03:13PM (4 children)
You might have an argument in the degenerate case -but even if your only axiom is "A is true", it's impossible to *prove* that A is true within that framework. Your axioms are *always* unprovable within the framework they create.
You can absolutely prove that everything else you've created within that framework is true if your axioms are true - but the axioms themselves can only ever be assumptions.
(Score: 1) by khallow on Friday February 02 2024, @04:10PM (3 children)
That's a different business. Within the framework, axioms are always true and hence, A is true would be trivially true. My point is that the system of logic is sufficiently limited that you can't construct statements that are unprovable within this framework.
(Score: 2) by Immerman on Friday February 02 2024, @05:14PM (2 children)
No, that's exactly what I'm talking about.
Not sure what you're trying to say, but virtually all statements possible within any given logical framework are unprovable - including the small subset that can be disproven.
Example:
If all crows are pink, then elephants are watermelons
is a perfectly valid logical statement that's completely unprovable. Almost all possible statements within any logical framework are similarly nonsensical, and thus unprovable.
(Score: 2) by Immerman on Friday February 02 2024, @05:27PM (1 child)
Wait, no, my bad - that's absolutely a provably true statement. All statements of the form
If [false] then ...
are true, since the "then" portion will never be invoked, so to prove it you only need to establish that a single non-pink crow exists.
But my point stands - the vast majority of possible statments within most logical systems will be nonsensical, and thus improvable.
The problem is that, while you can absolutely prove:
IF the axioms on which arithmetic is based are true, THEN 3+5 = 8.
You CANNOT prove
3+5=8
because the axioms on which the statement is based cannot themselves be proven.
(Score: 1) by khallow on Saturday February 03 2024, @06:38AM
And as I noted, you have a special class of unprovable statements which aren't unprovable because of nonsensicality.
Axioms are always true in the logical system by definition. When operating in a system of logic, they are their own proof.
Again, this is a different issue. In any system containing natural number axioms, one can come up with unprovable statements which do not conflict with the axioms of the system or are nonsensical. It's a deeper reason.