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: 0) by Anonymous Coward on Wednesday December 07 2016, @06:12AM
The problem with the "aliens did it" idea is that it could fit almost anything. The vagueness makes it uninteresting until all else is ruled out.
(Score: 0) by Anonymous Coward on Wednesday December 07 2016, @07:34AM
Thinking about the possibility more... The narrative is that humans used to think the earth was the center of the universe, then that it orbited the sun, then that the sun was a rather typical star orbiting the center of a galaxy consisting of >billions of other stars, amongst >billions of other galaxies. Extrapolating further, what if Earth is basically in the pit of an intergalactic quarry? All the most useful stuff has already been excavated, now all of value remaining in our section of the universe is the raw EM energy.
(Score: 0) by Anonymous Coward on Wednesday December 07 2016, @03:16PM
Or alternatively, we are actually latecomers because our galaxy (and the others with many stars) is not particularly life-friendly and thus it took a long time until we developed. This also explains why we haven't met extraterrestrials: In our galaxy there's only life on earth, and those in other galaxies are too far away for us to find them. Maybe in a billion years our galaxy will look star-starved, too, because by that time we'll have used up all those stars.
(Score: 0) by Anonymous Coward on Wednesday December 07 2016, @08:10PM
In our galaxy there's only life on earth
That's some statement to make. Over 500,000,000,000 stars, and most likely over 5,000,000,000,000 planets or planet-sized object, and we are the only planet with life? That's like a bacteria saying, since it didn't find any life in its half a second second it has been aware of its surroundings, that it is the only lifeform on this Earth. I would say, that some some fucking arrogant bacteria!
(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.
(Score: 0) by Anonymous Coward on Wednesday December 07 2016, @07:43AM
See? There's your dark matter.
(Score: 0) by Anonymous Coward on Wednesday December 07 2016, @02:36PM
Is this where the Shadows from Babylon 5 came from?
(Score: 0) by Anonymous Coward on Wednesday December 07 2016, @03:58PM
Definitely not. All of Babylon 5 takes place in single galaxy (with the exception of Third space, where the aliens come from some other dimension). The Shadows inhabited a world on the edge of the Galaxy, also know as The Rim. Of course JMS did make some classic mistakes where the Galaxy became synonymous with all of the Universe when Lorien remarked that he was the first being to achieve sentience in all of the Universe. I find that laughable at best. Maybe he was the first in our galaxy, but there is no way he could have traveled all of the universe with its endless amounts of galaxies. It has really irked me.
(Score: 4, Insightful) by bob_super on Wednesday December 07 2016, @07:43PM
We don't know shit about the cosmos ...
I mean, seriously. I grew up being told by a few adults that there probably wasn't other planets in the whole universe (sounded weird when we got so many), we found thousands as soon as we learnt how to look.
We knew everything about galaxies, and suddenly some says "hey this one has a giant black hole in it", to which other replied "well, that's an outlier". Fifteen minutes later, every galaxy has a massive black hole in the center.
Now there might be a whole of extra galaxies of a new type?
Now, we do know a lot about the cosmos. It's actually gobsmackingly amazing, how a bunch of tiny brains came up with so many models and theories, which explain most of what we observe millions of light-years away.
But if anyone tells you that we clearly know how it works, so we shouldn't waste our time paying people to keep looking, they aren't paying attention.
(Score: 0) by Anonymous Coward on Thursday December 08 2016, @03:05AM
welcome to science