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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
(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. I have always been here. ---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. I have always been here. ---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. I have always been here. ---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]