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Galactic Pancake Mystery Solved
mOoZik writes "According to the BBC, Astronomers have figured out why a series of small galaxies surrounding the Milky Way are distributed around it in the shape of a pancake. Theorists believed that the eleven dwarf galaxy companions should have a diffuse, spherical arrangement, but a University of Durham team used a supercomputer to show how the galaxies could take the pancake form without challenging cosmological theory."
The evil Egglons attack, wiping out most of breakfast.
Aha, now all that remains is to find a galaxy shaped like a bottle of maple syrup!
Send email from the afterlife! Write your e-will at Dead Man's Switch.
... and more credit ... (and to enhance discussion :) ...
Full article
The Distribution of Satellite Galaxies: The Great Pancake
Noam I Libeskind, Carlos S Frenk, Shaun Cole, John C Helly, Adrian Jenkins, Julio F Navarro and Chris Power
ABSTRACT
The 11 known satellite galaxies within 250 kpc of the Milky Way lie close to a great circle on the sky. We use high resolution N-body simulations of galactic dark matter halos to test if this remarkable property can be understood within the context of the cold dark matter cosmology. We construct halo merger trees from the simulations and use a semianalytic model to follow the formation of satellite galaxies. We find that in all 6 of our simulations, the 11 brightest satellites are indeed distributed along thin, disk-like structures analogous to that traced by the Milky Way's satellites. This is in sharp contrast to the overall distributions of dark matter in the halo and of subhalos within it which, although triaxial, are not highly aspherical. We find that the spatial distribution of satellites is significantly different from that of the most massive subhalos but is similar to that of the subset of subhalos that had the most massive progenitors at earlier times. The elongated disk-like structure delineated by the satellites has its long axis aligned with the major axis of the dark matter halo. We interpret our results as reflecting the preferential infall of satellites along the spines of a few filaments of the cosmic web.
CC.
TaijiQuan (Huang, 5 loosenings)
It's bunnies all the way down?
ClutterMe.com - easiest site creation on the Net. Just click and type.
Our local cluster is a franchise of IHOP (intergalactic house of pancakes).
... researchers are still working on the mystery of the cosmic sausage and eggs, as well as new puzzling information that seems to indicate the presence of a Great White Handkerchief... or maybe it's a napkin?
Dark Syrup explains galactic pancake mystery.
This sounds a little like planetary formation. What if these 'halos' were really rings, due to some sort of spin in the original setup? Do they have to be a 3-dimensional halo? I am not an astronomer, but it sounds reasonable to me - could someone please explain this?
Quoth the server, "404."
How much of this kind of research does NASA actually do? It seems that they largely put the satellites in place and maintain them, and universities handle the data analysis.
You can never go home again... but I guess you can shop there.
...on this pancake, Smucker's already has a patent on it.
NASA is about rockets. This isn't the sort of stuff they do really do. They help supply data to astronomers/cosmologists/physicists who apply to them, and who, largely, are affiliated with universities and are not "kids."
Dr. Feynman at CalTech and Dr. Sagan at Cornell, for instance, who were both rather famously at odds with NASA more often than not.
"Citizens" have always handled the bulk of astronomical research.
Because more often than not NASA is the necessary enemy of astronomers. It is a government agency, run for the government's purposes, complete with a government beauracracy, and only provisionally interested in theoretical science at all.
But they own Hubble.
I might also point out that these "kids" weren't even in America. England has a university or two worth a damn that might object to being catagorized as "random", and four or five smart people in them. Germany, China, Australia, and hell (as it were), even the Vatican have quite capable cosmologists of their own.
NASA isn't the center of the universe.
KFG
when's the galaxy due to flip over?
Well, maybe *you've* never heard of the University of Durham, but it's one of the foremost universities in the UK, and the Physics group there is extremely well-respected.
This isn't "some kids doing a group project", this is proper academic research; you may have heard of that...
It's official. Most of you are morons.
Angular Momentum
If you have a total angular momentum of 0, you get an eliptical galaxy. All stars have totally random orbital orientations around the center, so it gives an elipsoid. it COULD be a sphere (but what do you mean with gravitational stable? all galaxies are dynamic), but the chances are rather slim).
If there is a angular momentum, it will create a disc simply because thats a lower energy state with the same angular momentum compared to a sphere.
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
So what you're saying is that you have to have the matter in the galaxy orbit (more or less) around a common axis, like in our solar system.
What would cause this to happen, instead of there being a bunch of randomly-oriented orbits?
(I suppose I am making the critical assumption that the distribution of matter immediately after the big bang was uniform, and I'm sure any cosmologist would be happy to smack me down over that, but I'll ask anyway.)
So each galaxy should have non-zero angular momentum. This doesn't mean that there shouldn't be ANY spherical-like orbits, just that the majority of objects orbit in the "pancake" that is perpendicular to the axis of rotation. Here's the punchline: over billions of years, the objects that are NOT orbiting in the galaxy's pancake have close encounters with the more numerous objects in the pancake, and are either flung out of the galaxy or put into more normal orbits. The same process accounts for the fact that all planets in the Solar System orbit in a common plane (called the ecliptic plane).
As for elliptic galaxies, my impression was that they are the result of low-speed collisions between two spiral galaxies of roughly the same size. The two pancakes then combine to form a diffuse cloud of strars. For instance, when the Milky Way impacts Andromeda in 2 billion years (or is it 3? I can't remember), the result should be an elliptic galaxy if I understand the dynamics correctly.