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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: 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.