Galaxies Die By Slow "Strangulation" 42
HughPickens.com writes: BBC reports that results of a study of the spectrum of light emitted by 23,000 red, passive galaxies and 4,000 blue, star-forming ones shows that when galaxies stop making stars, their death is usually a slow process that chokes them of the necessary cool gases over about four billion years. Astronomers surveyed thousands of galaxies, living and dead, to assess whether the transition is rapid or slow. In the dead galaxies they detected high levels of metals, which build up during star formation and point to a slow strangulation process. "Metals are a powerful tracer of the history of star formation: the more stars that are formed by a galaxy, the more metal content you'll see," says Dr Yingjie Peng. "So looking at levels of metals in dead galaxies should be able to tell us how they died."
Astronomer Andrea Cattaneo from the Observatoire de Paris compares this tell-tale evidence to the high levels of carbon dioxide seen in a strangled human body. "During [strangulation], the victim uses up oxygen in the lungs but keeps producing carbon dioxide, which remains trapped in the body," wrote Dr Cattaneo. "Instead of building up CO2, the strangled galaxies accumulate metals — elements heavier than helium — produced by massive stars." On average, living, star-forming galaxies were four billion years younger than the dead ones. This matches the amount of time that the astronomers calculate would be needed for the galaxies to burn up their remaining gas supply during the strangulation. "This is the first conclusive evidence that galaxies are being strangled to death," says Peng. "What's next though, is figuring out what's causing it. In essence, we know the cause of death, but we don't yet know who the murderer is, although there are a few suspects."
Astronomer Andrea Cattaneo from the Observatoire de Paris compares this tell-tale evidence to the high levels of carbon dioxide seen in a strangled human body. "During [strangulation], the victim uses up oxygen in the lungs but keeps producing carbon dioxide, which remains trapped in the body," wrote Dr Cattaneo. "Instead of building up CO2, the strangled galaxies accumulate metals — elements heavier than helium — produced by massive stars." On average, living, star-forming galaxies were four billion years younger than the dead ones. This matches the amount of time that the astronomers calculate would be needed for the galaxies to burn up their remaining gas supply during the strangulation. "This is the first conclusive evidence that galaxies are being strangled to death," says Peng. "What's next though, is figuring out what's causing it. In essence, we know the cause of death, but we don't yet know who the murderer is, although there are a few suspects."
Overdramatic (Score:5, Interesting)
"Strangulation" seems to me an over-dramatic way of putting it. "Starvation" would be better. The supply of fresh hydrogen stops, so new stars stop being created. The old stars continue burning, some go supernova and blast out metals.Like when you stop adding wood to a fire, the logs already on the fire continue burning and the amount of ash increases.
All this suggests that there is not an indefinite supply of intergalactic hydrogen, so once the galaxy has pulled in all the hydrogen in its immediate vicinity, it will slowly starve.
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They made the distinction, and I agree they used the wrong verb. Perhaps "pillage" would have been better, since they suggested that other galaxies are stealing the hydrogen fuel sources.
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both words are overly simplistic for the process.
however you can use up all the local resources. It is called strip mining. So galaxy's are like people they strip mine an area of all useful stuff, and living behind a desert filled with rusting metallic husks.
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I agree, surprised to see exactly what I was going to say. It's possible the author is english as a second language or something, so I'll withold judgement, but Starvation is far more apt than strangulation. Strangulation implies an outside actor, starvation does not.
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Re:Overdramatic (Score:4, Insightful)
The authors of this work didn't invent the word -- that's been one of the standard descriptions of this process for decades, and I'm not sure who first came up with it. I think it evolved from "suffocation", which does make more sense (it runs out of gas).
This is in contrast to other dramatic ways of making a galaxy "red and dead" like "harassment", "tidal strippping", and "cannibalism", during which the galaxy undergoes "violent relaxation" (the single best technical term in all of astrophysics).
[TMB]
What about the quality of the remaining stars? (Score:2)
What if the galaxy with many fewer stars has higher quality stars? Should we give so much credit to galaxies that are prolific star creators when they have poached the material from other galaxies?
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Indeed. We have been trolled by attention-seeking astronomers.
Asimov suggested thahe answer to The Last Question (Score:2)
is "Let there be Light".
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Yes and these esteemed scientists have come to that possible conclusion a long time before you and called it "heat death".
Death of a Galaxy (Score:4, Funny)
What about battery failure? I have only had my Galaxy Note 3 for two and a half years so it hasn't happened yet
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Probably a stupid question but... (Score:1)
Why do astronomers use the word "metal" to mean anything heavier than helium? I get that there's a lot of hydrogen and helium out there, and it might be useful to distinguish those from everything else but... why "metal"? Is it just that nobody mentioned that that word was already in use or is there a better reason that that?
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See metallicity [wikipedia.org].
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See metallicity [wikipedia.org].
Your link only reaffirms what GP already recognized: astronomers combine all elements except hydrogen and helium into one large group calls "metals" and then measure an object's "metallicity". The question that was asked is why did astronomers choose to use the specific word "metal"? The word already had a very specific meaning in science and in common usage. So were the astronomers just being lazy or was there more meaning to the decision?
That's not how strangulation works (Score:4, Interesting)
During strangulation, the jugular vein is pressed shut, leading to vascular congestion in the brain (which is how you get the telltale petechiae); the backpressure eventually prevents the influx of oxygenated blood to the brain, which is subsequently starved of oxygen. It's actually quite difficult to squeeze somebody's windpipe shut.
(Do you really *want* to know why I know this?)
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yes. tell us. but keep your distance.
a couple of points (Score:4, Informative)
1) just to be clear, when he says "metals" are everything more than helium, that's an astronomer thing.
2) IANAA, but the whole 'stellar starvation' thing seems logically obvious due to the iron peak - as galaxies feed on their hydrogen, their suns fuse it up all the way to iron, then they no longer are generating energy from subsequent fusion, merely consuming it (elements above iron are normally only created persistently from supernovae), ergo, once a galaxy has climbed the fusion-energy curve up to iron, beyond that it's go nowhere to go except collapse and ultimate I'd guess black hole status?
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Don't forget the other piece of the puzzle, supernova remmnants slide back down the curve and decay to lead. As far as everything collapsing into a black hole, that doesn't seem to be likely. Space is too damn big and getting bigger. This whole expanding universe observation remains quite confounding. It will likely be several centuries before we figure it out. Mostly because we are fixated on selling each other insurance rather than focusing on our mission.
I liked the universe a lot better before the poli
So...Death Metal? (Score:2)
How very "Rock and Roll"!
Round up the usual suspects (Score:3)
"This is the first conclusive evidence that galaxies are being strangled to death," says Peng. "What's next though, is figuring out what's causing it. In essence, we know the cause of death, but we don't yet know who the murderer is, although there are a few suspects."
It was Colonel Mustard with the rope in the Virgo Supercluster.
thought of alzheimer's plaque buildup (Score:2)
Sounds like Alzheimer's disease. Materials that are not useful and build up in a healthy system, causing the breakdown or choking off of the normal process. And it doesn't sound like there's a cure for galaxies, either, other than a "Big Crunch" flushing mechanism (which has been generally dismissed).
Scary thouht (Score:2)
anthropomorphism (Score:2)
It's silly to talk about galaxies this way. Not to mention, older galaxies like this are probably much MORE likely to harbor LIFE.