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from the it's-a-galaxy-Jim,-but-not-as-we-know-it dept.
Not all galaxies sparkle with stars. Galaxies as wide as the Milky Way but bereft of starlight are scattered throughout our cosmic neighborhood. Unlike Andromeda and other well-known galaxies, these dark beasts have no grand spirals of stars and gas wrapped around a glowing core, nor are they radiant balls of densely packed stars. Instead, researchers find just a wisp of starlight from a tenuous blob.
"If you took the Milky Way but threw away about 99 percent of the stars, that's what you'd get," says Roberto Abraham, an astrophysicist at the University of Toronto.
How these dark galaxies form is unclear. They could be a whole new type of galaxy that challenges ideas about the birth of galaxies. Or they might be outliers of already familiar galaxies, black sheep shaped by their environment. Wherever they come from, dark galaxies appear to be ubiquitous. Once astronomers reported the first batch in early 2015 — which told them what to look for — they started picking out dark denizens in many nearby clusters of galaxies. "We've gone from none to suddenly over a thousand," Abraham says. "It's been remarkable."
(Score: 4, Interesting) by frojack on Wednesday December 07 2016, @06:14AM
Are there enough of these to account for all the dark matter?
No, you are mistaken. I've always had this sig.
(Score: 2, Insightful) by anubi on Wednesday December 07 2016, @07:03AM
Damn, that's a good question...
Maybe these are galaxies whose gravitational forces have yet to make the star matter dense enough to ignite? Or an entire galaxy that has already spent its life.
I wonder if Stephen Hawking's "evaporating black holes" cause hydrogen formation elsewhere ( like here ), and - over time - lots of it - stars gradually coalesce to the point of enough hydrogen under enough gravitational pressure to ignite the nuclear burn.
I'm biased somewhat to the latter, as once ignited, stars burn at various rates, some fast, some very slow. Seems like there should be remnants of the little slow burning ones long after the big ones have burned themselves out.
But then, maybe, what if what they are seeing is basically fields of cold iron? Seems like even that would gravitationally coalesce into a black hole, and if Hawking is right, evaporate.
Sure trashes a lot of what I understood thermodynamics to be, but maybe, just maybe, those laws do not apply at all times - regardless of how I observe them to be in the limited arena I have seen them function in.
I find it hard to believe thermodynamics can run in reverse like that, but there have been many things people believed that turned out later, just ain't so.
Its stuff like this which sure pique my curiosity. I do not know why knowing such a thing would be fulfilling, as it has nothing to do with my next meal, but it does.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 1, Interesting) by Anonymous Coward on Wednesday December 07 2016, @02:00PM
Or an entire galaxy that has already spent its life.
Considering that red dwarf stars are the most common and they are estimated to burn for a trillion years if we're finding galaxies that have indeed exhausted themselves already then we've got some fundamental ideas about the universe that would turn out to be very wrong: either it's way older than previously thought or stars actually burn much faster than thought (meaning that our sun doesn't really have much time left compared to previous estimates.)
(Score: 1, Interesting) by Anonymous Coward on Wednesday December 07 2016, @03:21PM
Or maybe red dwarfs are not really the most common in all the galaxies, and we only think they are the most common because of selection bias: Those galaxies where red dwarfs are uncommon might be exactly those which now look star-starved because all those big bright stars they once had are already dead. Since for a long time we only observed the star-rich galaxies, we've seen the distribution of stars in those, and assumed that this is the star distribution in general.
(Score: 0) by Anonymous Coward on Wednesday December 07 2016, @12:24PM
What about galactic rotation curves?
(Score: 0) by Anonymous Coward on Wednesday December 07 2016, @01:17PM
and the CMWB.
(Score: 0) by Anonymous Coward on Wednesday December 07 2016, @04:40PM
I only ever see it as CMB, microwave being one word usually.