Milky Way's Graveyard of Dead Stars Found (phys.org) 44
The first map of the "galactic underworld" -- a chart of the corpses of once massive suns that have since collapsed into black holes and neutron stars -- has revealed a graveyard that stretches three times the height of the Milky Way, and that almost a third of the objects have been flung out from the galaxy altogether. Phys.Org reports: "These compact remnants of dead stars show a fundamentally different distribution and structure to the visible galaxy," said David Sweeney, a Ph.D. student at the Sydney Institute for Astronomy at the University of Sydney, and lead author of the paper in the latest issue of Monthly Notices of the Royal Astronomical Society. "The 'height' of the galactic underworld is over three times larger in the Milky Way itself," he added. "And an amazing 30 percent of objects have been completely ejected from the galaxy." [...] Sweeney added that "the hardest problem I had to solve in hunting down their true distribution was to account for the 'kicks' they receive in the violent moments of their creation. Supernova explosions are asymmetric, and the remnants are ejected at high speed -- up to millions of kilometers per hour -- and, even worse, this happens in an unknown and random direction for every object." But nothing in the universe sits still for long, so even knowing the likely magnitudes of the explosive kicks was not enough: the researchers had to delve into the depths of cosmic time and reconstruct how they behaved over billions of years.
The intricate models they built -- together with University of Sydney Research Fellow Dr. Sanjib Sharma and Dr. Ryosuke Hirai of Monash University -- encoded where the stars were born, where they met their fiery end and their eventual dispersal as the galaxy evolved. The final outcome is a distribution map of the Milky Way's stellar necropolis.
In the maps generated, the characteristic spiral arms of the Milky Way vanish in the 'galactic underworld' version. These are entirely washed out because of the age of most of the remnants, and the blurring effects of the energetic kicks from the supernovae which created them. Even more intriguing, the side-on view shows that the galactic underworld is much more 'puffed up' than the Milky Way -- a result of kinetic energy injected by supernovae elevating them into a halo around the visible Milky Way. "One of the problems for finding these ancient objects is that, until now, we had no idea where to look," said Sydney Institute for Astronomy's Professor Peter Tuthill, co-author on the paper. "The oldest neutron stars and black holes were created when the galaxy was younger and shaped differently, and then subjected to complex changes spanning billions of years. It has been a major task to model all of this to find them."
"It's a little like in snooker," said Sweeney. "If you know which direction the ball is hit, and how hard, then you can work out where it will end up. But in space, the objects and speeds are just vastly bigger. Plus, the table's not flat, so the stellar remnants go on complex orbits threading through the galaxy." He added: "Finally, unlike a snooker table, there is no friction -- so they never slow down. Almost all the remnants ever formed are still out there, sliding like ghosts through interstellar space."
The intricate models they built -- together with University of Sydney Research Fellow Dr. Sanjib Sharma and Dr. Ryosuke Hirai of Monash University -- encoded where the stars were born, where they met their fiery end and their eventual dispersal as the galaxy evolved. The final outcome is a distribution map of the Milky Way's stellar necropolis.
In the maps generated, the characteristic spiral arms of the Milky Way vanish in the 'galactic underworld' version. These are entirely washed out because of the age of most of the remnants, and the blurring effects of the energetic kicks from the supernovae which created them. Even more intriguing, the side-on view shows that the galactic underworld is much more 'puffed up' than the Milky Way -- a result of kinetic energy injected by supernovae elevating them into a halo around the visible Milky Way. "One of the problems for finding these ancient objects is that, until now, we had no idea where to look," said Sydney Institute for Astronomy's Professor Peter Tuthill, co-author on the paper. "The oldest neutron stars and black holes were created when the galaxy was younger and shaped differently, and then subjected to complex changes spanning billions of years. It has been a major task to model all of this to find them."
"It's a little like in snooker," said Sweeney. "If you know which direction the ball is hit, and how hard, then you can work out where it will end up. But in space, the objects and speeds are just vastly bigger. Plus, the table's not flat, so the stellar remnants go on complex orbits threading through the galaxy." He added: "Finally, unlike a snooker table, there is no friction -- so they never slow down. Almost all the remnants ever formed are still out there, sliding like ghosts through interstellar space."
I wonder (Score:2)
What type of undiscovered materials and chemical elements are found on those leftover stars and planets.
Re: I wonder (Score:3)
Pretty much the same ones we have here. Possibly in differing concentrations. But unless Mendeleev forgot a row or two, nothing remarkable.
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>Pretty much the same ones we have here.
Probably, simply because the mechanisms to produce them were the same everywhere (we assume).
However, there's still an unlimited amount of room at the bottom of the table.
As elements get heavier they tend to become less common in nature (since it takes an ever increasing amount of energy per gram to create them), as well as generally becoming more unstable as the number of protons increases, so that heavier elements tend to decay into lighter ones over the billions
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Lots and lots of unobtainium.
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Not made of Chemical Elements (Score:4, Informative)
What type of undiscovered materials and chemical elements are found on those leftover stars and planets.
First, nothing has been found. This is merely a theoretical simulation used to predict where such objects might be whether it is correct depends on whether the assumptions used to generate the simulation are accurate. Second, these are neither "leftover stars" or planets - they are the cinders of dead stars that have exhausted their nuclear fuel and undergone a supernova explosion leaving behind either a neutron star or black hole. Neither object is made of traditional atomic matter so there are no chemical elements really involved.
For neutron stars the potential discoveries there are not new chemical elements but completely new states of matter such as a QCD colour superconductor or stable strange-matter (matter including strange quarks). This is where the pressures and densities become so extreme that quarks start to behave very differently to how they behave in atomic nuclei. So far all of these states are theoretical but it may be possible to see evidence of them in heavy ion collisions at colliders or from studying the detailed behaviour of neutron stars.
No mention of Dark Matter? (Score:2)
It's even a distributed halo.
Re:No mention of Dark Matter? (Score:4, Insightful)
That was my first thought as well - but they say only ~30% of objects were ejected from the milky way, and those remnants are probably only a small fraction of the mass of the original star - so probably less than 10% of the visible mass of the galaxy.
Far less than the 85% of mass that's supposed to be dark matter to hold our galaxy together.
So... probably not.
However, the estimated concentration could be way off, and having such a known-matter halo (with its associated frame dragging) might have significant effects on our models of early galactic formation, which in turn could significantly change our dark mass estimates.
Seems like we keep encountering new partial solutions to the dark matter puzzle - including some alternate theories that mostly eliminate it - but tend to get dismissed because they only *mostly* eliminates it, and a new theory that doesn't actually describe reality accurately justifiably faces an uphill battle.
But every time we discover another family of non-luminous objects that infringes on Dark Matter territory, it lowers the bar for alternate theories. It may even be that the "solution" to dark matter has already been formulated as an alternate theory of gravity, just waiting for enough non-luminous matter to be discovered so that it can explain away the rest and accurately fit the data.
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Interesting (Score:5, Interesting)
Re: Interesting (Score:2)
"Undetectableâ non-radiating compact objects like these can be detected through gravitational micro lensing when they pass in front of a light source, with detection events increasing in frequency the more of them there are.
The frequency of detection events would probably depend upon the spacial density of light sources in line with each object as well. Off the Milky Way's central plane, there are fewer of these. And so fewer opportunities to detect the lensing of their light.
But I'm prety sure that smart astrophysicists can account for this distribution ith s few well placed fudge factors.
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>Off the Milky Way's central plane, there are fewer of these.
I don't believe so. After all, all the stars in the Milky way are closer to us than these ejected objects, and thus unsuitable. The only candidate light sources further away than the gravitational lenses are other galaxies, which don't care about the Milky Way's plane. In fact I seem to recall hearing that most intergalactic astronomy focuses outside the galactic plane, simply because within the plane there's too many stars cluttering the vi
Not the same distribution (Score:2)
It’s interesting that the distribution is similar to many dark matter models, despite themselves not making up nearly enough mass.
Not really - the Dark Matter halo extends out to several times the radius of the disc making it much, much larger. These objects are only predicted to extend beyond the visible galaxy perpendicular to the disc.
If dark matter exists as a particle these compact masses will stir them up a bit
Not really given the size of the halo compared to the number of these objects - in the same way that a butterfly does not "stir up" the Earth's atmosphere (notwithstanding chaos effects). However, what would be interesting is that if these predictions are correct then finding these objects moving th
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the Dark Matter halo extends out to several times the radius of the disc making it much, much larger. These objects are only predicted to extend beyond the visible galaxy perpendicular to the disc.
Yes, so does this model. Did you not read the article? Three times thicker in the center, and if you look at the overlay in the article near the bottom it’s visibly about 3x the diameter as well. Given the distribution shown it’s well over 30 times the volume.
Not really given the size of the halo compared to the number of these objects - in the same way that a butterfly does not "stir up" the Earth's atmosphere (notwithstanding chaos effects).
While they are currently a small say 0.4% of the mass of the milky way, the concentration of mass means that all particles with mass, which includes hypothetical dark matter, will feel the gravitation. It would tend to puff up if not
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Yes, so does this model. Did you not read the article?
Yes I did read it - did you read my comment, including the bit you even quoted where I said that they _only_ extend beyond the galaxy _perpendicular_ to the disc? Do you understand the basic shape and dimensions of our galaxy? Our galaxy is about 1,000 light years thick and about 52,000 light years in radius. So while the roughly spherical distribution of these compact objects extends beyond the galaxy perpendicular to the disc i.e. beyond the 1000ly thickness of the disc they come nowhere near to extendi
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Where are you getting your information? It’s paywalled and the article states contrary evidence to your claims as I have outlined above.
What article are you reading? The one linked shows a roughly spherical distribution of objects in the first figure at the top - there is a very small bulge where the disk is in the side-on view. In addition, the article actually quotes the author as saying:
These compact remnants of dead stars show a fundamentally different distribution and structure to the visible galaxy
which is consistent with the spherical image shown being very different to the disc structure of the visible galaxy. The information about Dark Matter comes from memory because I'm a particle physicist who has searched for DM in the past but you can loo
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What article are you reading? The one linked shows a roughly spherical distribution of objects in the first figure at the top - there is a very small bulge where the disk is in the side-on view. In addition, the article actually quotes the author as saying:
These compact remnants of dead stars show a fundamentally different distribution and structure to the visible galaxy
Yes, because not only is it much larger, in every direction, the distribution within it is also not the same as visible matter. It is exactly as I said. The relevant picture is the side on view where you can clearly see the size as 3x wider (or thereabouts). Yes, I know the truth can be hard to concede.
difference is no where near 20-orders of magnitude
The atmosphere is the atmosphere weighs about 5.5 quadrillion tons while the mass ejected already per the article is 0.4% making that butterfly weigh 22 trillion tons. Given the mass, based of a typical wi
Not actually found (Score:2)
Reading the article, not actually "found".
The location of these dead stars has now been hypothesized.
Re: (Score:3, Funny)
“Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.”
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Typical; yesterday I had 15 mod points and nothing to spend them on. Today, an insightful comment, and no points.
Virtual mod up.
Astrophysicists use words differently - to them "metals" are elements other than hydrogen and helium. Found means predicted. Known means guessed. OK, it's ridiculously hard to do experiments at 1,000 light years, but just 'cos your models don't contradict each other, it doesn't make any of them "proven".
Snooker (Score:2)
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Yes, have to agree. Even limited exposure to what we know now and are discovering about the universe - size, origin, trajectory - makes one think hard about where it all comes from, and where we came from.
The fundamental question scientists are tying to answer, whether they admit it or not, is about origins, both of the universe and ourselves, and in the end its a religious question in a very broad sense, its about creation and meaning.
One has the sense that in trying to get a handle on these questions we
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This may come as a complete shock to you but Science is amoral by definition. That is, by definition it has NO mention of morality.
Science is a quest for Truth by removing falsehoods.
If you want to debate the moral / most efficient use of resources to pursue that goal that's what Philosophy is for. =P
--
Someday Scientists will (re)discover the THREE types of intellect: Knowledge, Emotional, Spiritual.
Re:So what, just more overpriced useless 'knowledg (Score:4, Interesting)
Not sure if you're a troll, or just an ignorant idiot.
Done by universities. And look at money spent on science: in the US, the NIH was getting about $30B a year; ditto for NASA. Meanwhile, the US military budget (that we're allowed to know about is half the budget, over ONE TRILLION DOLLARS.
So shut up, and complain to your representatives to cut the damn military budget.
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The total budget is over $5 Trillion, the military is not nearly half of it. Stop inventing bullshit.
Re: So what, just more overpriced useless 'knowled (Score:2)
The total published budget. There's also a dark budget that doesn't get published and is therefore of unknown size.
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It's theory - we haven't spotted the things. They've hypothesized that such a cloud of ejected objects should exist based on events that we know happen within the galaxy.
We know they belong to us, (assuming they actually exist) because our only excuse for suspecting they exist is because we should have created them while getting to where we're at.
This is theoretical simulation, not observations (Score:5, Informative)
For those who did not read the paper: the paper starts with a model of the stellar population of the Milky Way, and a model for stellar evolution, and predicts the positions of stellar remnants (black holes and neutron stars). It is not a catalog of actual black holes and neutron stars observed by astronomers.
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They don't even have to hit us. If the likelihood of one passing near us in any given period of time is high enough, then we could have yet another explanation for the Fermi Paradox.
Release a large number of blind rabbits on the expressway at r
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The effects on the solar system of having a few solar mass black hole cruise by within 65ly (or less than that for a neutron star) are exactly the same as having a normal star of the same mass do so. And there are plenty of them already within 65ly.
The one way a compact object differs is that if there's a companion star dumping gas into it, you get X-rays. But these are a) much more rare; b) not in the "invisible" population being discussed in this paper, and c) I suspect you'd still have to be either pre
Solar System diameter -- .00127 light years [n/t] (Score:1)
[n/t]
Re: Solar System diameter -- .00127 light years [n (Score:2)
2 ly, if you include the port cloud.
It's October (Score:2)
The graveyard stories are raining their ugly skeleton heads.
Missing mass of the universe? (Score:2)
This is a generic question about recent discoveries such as this one. As the JWST looks further and further out into the cosmos, it keeps seeing more galaxies and stars than we were previously able to with Hubble or other means.
Now we have this finding of a dead star graveyard within our own galaxy.
Taken as a whole, do these new findings alter the total mass of the universe in our calculations such that the idea of dark matter making up what we can't find becoming less likely? Or has all this "stuff" alrea
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To be clear this is a theoretical "discovery" - we haven't actually spotted anything, a group has just hypothesized that they should exist based on past events we know have happened.
As for discovering more stuff with more powerful telescopes... Mostly the more powerful telescopes are looking at galaxies ever further away (and closer to the beginning of the universe). And yeah, we've mostly assumed that the entire universe is just an infinite expanse of places more or less like here. With some large-scale
Throwaway Universe? (Score:2)
And here I thought only human beings could invent a throwaway society.
Mother Nature has 1-upped us all by showing that the Universe appears to operate on both recycling principles (blackholes) and throw it out of the Galaxy concepts.