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Dark Halo Around Our Galaxy Looks Like Squished Beach Ball
Of course, not mentioned in the article is the fact that this shape of
"dark matter halo" matches the configuration one might see with MOND. Yousuf Khan +++ SPACE.com -- Dark Halo Around Our Galaxy Looks Like Squished Beach Ball "But the new study found that the Milky Way's halo isn't exactly spherical, but squished. In fact, its beach-ball form is flattened in a surprising direction — perpendicular to the galaxy's visible, pancake-shaped spiral disk." http://www.space.com/scienceastronom...milky-way.html |
#2
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Dark Halo Around Our Galaxy Looks Like Squished Beach Ball
On Jan 8, 8:02*am, Yousuf Khan wrote:
Of course, not mentioned in the article is the fact that this shape of "dark matter halo" matches the configuration one might see with MOND. * * * * Yousuf Khan +++ SPACE.com -- Dark Halo Around Our Galaxy Looks Like Squished Beach Ball "But the new study found that the Milky Way's halo isn't exactly spherical, but squished. In fact, its beach-ball form is flattened in a surprising direction — perpendicular to the galaxy's visible, pancake-shaped spiral disk."http://www.space.com/scienceastronomy/100106-dark-matter-halo-milky-w... my comment: it's - its dolts Yer conjectures are junk. It's very clear the halo's shape is due to stronger gravity in-dish than in-axle. And there are no black holes: http://twitter.com/alysdexia/status/4323682209 http://groups.google.com/group/sci.p...43fbaaf3d4dfbb |
#3
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Dark Halo Around Our Galaxy Looks Like Squished Beach Ball
Yousuf Khan wrote:
Of course, not mentioned in the article is the fact that this shape of "dark matter halo" matches the configuration one might see with MOND. MOND is a heuristic, so that is sorta expected. But MOND doesn't actually predict extra matter, just modified gravity. Which is why MOND has been soooo quiet since 2006, because weak lensing surveys **** all over it. Yousuf Khan +++ SPACE.com -- Dark Halo Around Our Galaxy Looks Like Squished Beach Ball "But the new study found that the Milky Way's halo isn't exactly spherical, but squished. In fact, its beach-ball form is flattened in a surprising direction ? perpendicular to the galaxy's visible, pancake-shaped spiral disk." http://www.space.com/scienceastronom...er-halo-milky- way.html While it would be dishonest to say the result is 100% expected, I am not sure why it is phrased like everyone is surprised. Dark matter halos of other galaxies don't have spherical symmetry so why should ours? Just because it simplifies computations doesn't make it a correct physical model. |
#4
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Dark Halo Around Our Galaxy Looks Like Squished Beach Ball
Dear Yousuf Khan:
On Jan 8, 9:02*am, Yousuf Khan wrote: Of course, not mentioned in the article is the fact that this shape of "dark matter halo" matches the configuration one might see with MOND. Actually, no, it contravenes MOND. We expected our Dark Matter halo to look like Andromeda's halo. +++ SPACE.com -- Dark Halo Around Our Galaxy Looks Like Squished Beach Ball "But the new study found that the Milky Way's halo isn't exactly spherical, but squished. In fact, its beach-ball form is flattened in a surprising direction — perpendicular to the galaxy's visible, pancake-shaped spiral disk. snip link now broken by Google.Groups So, why would our Dark Matter halo be arranged differently than Andromeda's? Would this hint we are actually the convergence of two galaxies? I am assuming from the description, that ours is taller than it is wide... David A. Smith |
#5
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Dark Halo Around Our Galaxy Looks Like Squished Beach Ball
dlzc wrote:
Dear Yousuf Khan: On Jan 8, 9:02 am, Yousuf Khan wrote: Of course, not mentioned in the article is the fact that this shape of "dark matter halo" matches the configuration one might see with MOND. Actually, no, it contravenes MOND. We expected our Dark Matter halo to look like Andromeda's halo. I have not seen anything which states what the shape of the Andromeda halo is. It's probably just assumed to be spherical, like the Milky Way's halo was assumed to be. Or spherical-flattened, wider in the direction of the equator rather than the poles. Actually, Eric Gisse just said that it's known that the dark matter halos of other galaxies isn't spherical either, therefore it shouldn't be surprising that the Milky Way's isn't either. I'm not sure why he states that, but perhaps he's seen some articles about other galaxies' halos? As for the MOND interpretation. A physical description of MOND would be that gravity is strongest towards the centre, rapidly dropping off in strength as it travels further out from the centre, until it gets to a standard tipping point where the gravity drops in strength at a slower pace. That seems to describe the picture of this NFL football-shaped shape. SPACE.com -- Dark Halo Around Our Galaxy Looks Like Squished Beach Ball "But the new study found that the Milky Way's halo isn't exactly spherical, but squished. In fact, its beach-ball form is flattened in a surprising direction — perpendicular to the galaxy's visible, pancake-shaped spiral disk. snip link now broken by Google.Groups So, why would our Dark Matter halo be arranged differently than Andromeda's? Would this hint we are actually the convergence of two galaxies? I am assuming from the description, that ours is taller than it is wide... I don't know, as I said I've not seen a description of Andromeda's halo enough to compare. As for whether we're the convergence of two galaxies, the answer would have to be yes, and perhaps way more than two. But I assume you're talking about a recent merger of two galaxies. In that case, the answer would again have to be yes, as they mapped the halo by mapping the distribution of star streamers from the Sagittarius Dwarf Galaxy as it gets torn apart by the Milky Way, prior to full merger. But I think you're probably not even thinking of that kind of a merger. You're probably thinking of two galaxies whose disks are aligned and are landing on top of each other like a couple of flying saucers? Yousuf Khan |
#6
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Dark Halo Around Our Galaxy Looks Like Squished Beach Ball
Sam Wormley wrote:
On 1/8/10 10:02 AM, Yousuf Khan wrote: Of course, not mentioned in the article is the fact that this shape of "dark matter halo" matches the configuration one might see with MOND. Haven't we had this discussion previously? Dark Matter Exists - Sean Carroll snip In case you haven't noticed, I have rejected your standard template. Yousuf Khan |
#7
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Dark Halo Around Our Galaxy Looks Like Squished Beach Ball
eric gisse wrote:
Yousuf Khan wrote: Of course, not mentioned in the article is the fact that this shape of "dark matter halo" matches the configuration one might see with MOND. MOND is a heuristic, so that is sorta expected. But MOND doesn't actually predict extra matter, just modified gravity. Which is why MOND has been soooo quiet since 2006, because weak lensing surveys **** all over it. I'm actually just referring to the family of theories of which MOND is the parent. But since the original MOND has been found to be quite accurate at predicting all things about individual galaxies, it can stand as the torchbearer for its family here. It's easier to calculate than its successors like TeVeS. It's kinda like why would you do Einsteinian calculations in situations when Newton's laws are sufficient? Besides, once Dark Energy has moved all other galaxies away from us, and this is the only galaxy left in the visible universe, MOND is all you'll ever need to calculate anything. :-) While it would be dishonest to say the result is 100% expected, I am not sure why it is phrased like everyone is surprised. Dark matter halos of other galaxies don't have spherical symmetry so why should ours? Just because it simplifies computations doesn't make it a correct physical model. I have not seen any descriptions of the shapes of DM halos of other galaxies, whether symmetrical or non-symmetrical or anything. To what are you referring to when you say it's not totally surprising? Yousuf Khan |
#8
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Dark Halo Around Our Galaxy Looks Like Squished Beach Ball
Dear Yousuf Khan:
On Jan 9, 8:46*am, Yousuf Khan wrote: Dear Yousuf Khan: On Jan 8, 9:02 am, Yousuf Khan wrote: Of course, not mentioned in the article is the fact that this shape of "dark matter halo" matches the configuration one might see with MOND. Actually, no, it contravenes MOND. *We expected our Dark Matter halo to look like Andromeda's halo. I have not seen anything which states what the shape of the Andromeda halo is. There are a number of links that describe its distribution. It is an "oblate spheroid", more or less like the Earth. A little thinner along the spin axis than radially outwards. It's probably just assumed to be spherical, like the Milky Way's halo was assumed to be. Or spherical-flattened, wider in the direction of *the equator rather than the poles. This is right, but it is actually measured, based on proper star motion. Actually, Eric Gisse just said that it's known that the dark matter halos of other galaxies isn't spherical either, He's wrong. (For once.) therefore it shouldn't be surprising that the Milky Way's isn't either. But ours sounds to be tall and skinny, while Andromeda, with roughly similar motion, is short and stout. I'm not sure why he states that, but perhaps he's seen some articles about other galaxies' halos? As for the MOND interpretation. A physical description of MOND would be that gravity is strongest towards the centre, rapidly dropping off in strength as it travels further out from the centre, until it gets to a standard tipping point where the gravity drops in strength at a slower pace. That seems to describe the picture of this NFL football- shaped shape. MOND depends on acceleration to form a local g, which derives a shape based on the matter present and its motion. Andromeda does not look all that different from what we think we look like. But our Dark Matter halos are distinctly different. SPACE.com -- Dark Halo Around Our Galaxy Looks Like Squished Beach Ball "But the new study found that the Milky Way's halo isn't exactly spherical, but squished. In fact, its beach-ball form is flattened in a surprising direction — perpendicular to the galaxy's visible, pancake-shaped spiral disk. snip link now broken by Google.Groups So, why would our Dark Matter halo be arranged differently than Andromeda's? *Would this hint we are actually the convergence of two galaxies? *I am assuming from the description, that ours is taller than it is wide... I don't know, as I said I've not seen a description of Andromeda's halo enough to compare. I found an extensive paper that showed mass distribution as an angle above the ecliptic. But I also found this: http://www.solstation.com/x-objects/andromeda.htm "As a result, some astronomers believed that that one nucleus may be the remains a smaller satellite galaxy that was "eaten" by Andromeda" As for whether we're the convergence of two galaxies, the answer would have to be yes, and perhaps way more than two. But I assume you're talking about a recent merger of two galaxies. Not too recent, or we'd see more structure to the tall thin part of the Dark Matter halo. It would precess over time, slowly winding into "arms", then into a football shape. If the consumed galaxy were "edge- on". Would explain the number of out-of-ecliptic objects we have... In that case, the answer would again have to be yes, as they mapped the halo by mapping the distribution of star streamers from the Sagittarius Dwarf Galaxy as it gets torn apart by the Milky Way, prior to full merger. But I think you're probably not even thinking of that kind of a merger. You're probably thinking of two galaxies whose disks are aligned and are landing on top of each other like a couple of flying saucers? Not with the shape of the DM halo. At one angle, they'd look like a plus sign, or an X. David A. Smith |
#9
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Dark Halo Around Our Galaxy Looks Like Squished Beach Ball
On 1/9/10 10:15 AM, Yousuf Khan wrote:
In case you haven't noticed, I have rejected your standard template. Yousuf Khan Because you like to cling to MOND that fails where GTR succeeds? |
#10
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Dark Halo Around Our Galaxy Looks Like Squished Beach Ball
dlzc wrote:
On Jan 9, 8:46 am, Yousuf Khan wrote: I have not seen anything which states what the shape of the Andromeda halo is. There are a number of links that describe its distribution. It is an "oblate spheroid", more or less like the Earth. A little thinner along the spin axis than radially outwards. It's probably just assumed to be spherical, like the Milky Way's halo was assumed to be. Or spherical-flattened, wider in the direction of the equator rather than the poles. This is right, but it is actually measured, based on proper star motion. Then I suggest that the discrepancy could be based on the method used to measure the halo. One method is using halo star motion, while the other method is using star streamers from a dwarf galaxy. Halo stars are long-time residents settled down in their current positions years ago. Star streamers from an external dwarf galaxy are a more violent, recently introduced star group which haven't settled down yet. As for the MOND interpretation. A physical description of MOND would be that gravity is strongest towards the centre, rapidly dropping off in strength as it travels further out from the centre, until it gets to a standard tipping point where the gravity drops in strength at a slower pace. That seems to describe the picture of this NFL football- shaped shape. MOND depends on acceleration to form a local g, which derives a shape based on the matter present and its motion. Andromeda does not look all that different from what we think we look like. But our Dark Matter halos are distinctly different. It's been suggested that Andromeda's bulge is small compared to its disk, compared to ours. Maybe the halo is a proxy for the mass of the bulge? Ours might be more massive? Not necessarily the relative size of the central black holes, but the entire bulge mass, including stars. I don't know, as I said I've not seen a description of Andromeda's halo enough to compare. I found an extensive paper that showed mass distribution as an angle above the ecliptic. But I also found this: http://www.solstation.com/x-objects/andromeda.htm "As a result, some astronomers believed that that one nucleus may be the remains a smaller satellite galaxy that was "eaten" by Andromeda" Yes, I remember reading about the possible Andromeda double-nucleus. It could be the remains of another galaxy. Looks like they still haven't figured out what it can be. One group claims that the smaller nucleus is just a knot of stars in a young blue cluster, travelling through the bigger, older, redder central cluster of the galactic nucleus. *** I also found the following quote from the same link above: "Although Andromeda was long thought to be the most massive galaxy in the Local Group, recent data suggest that Andromeda's visible mass may total around 300 to 400 billion Solar-masses. This is considerably less than more recent estimates of the Milky Way's visible mass of as much as 600 billion or more Solar-masses, which suggests that the Milky Way may be much denser than Andromeda. These results apparently have been confirmed by recent estimates of the total halo masses of the two spirals that account for the gravitational effects of their invisible dark matter, which suggest that Andromeda has a total of around 700 billion to 1.2 trillion Solar-masses compared to 0.93 to 1.9 trillion or more for the Milky Way (more discussion from (Xue et al, 2008; Evans et al, 2000; and Evans and Wilkinson, 2000)." http://www.solstation.com/x-objects/andromeda.htm This seems to indicate that somehow the Milky Way might be a denser galaxy than Andromeda. If it's denser, then its halo might be similarly compatified. But I think you're probably not even thinking of that kind of a merger. You're probably thinking of two galaxies whose disks are aligned and are landing on top of each other like a couple of flying saucers? Not with the shape of the DM halo. At one angle, they'd look like a plus sign, or an X. Oh! Well, in that case we'd have seen more massive disruption in our galactic shape right now. Another thought, there's recent thought that our galaxy is a barred spiral, whereas Andromeda is a standard spiral. Perhaps the bar in the galactic bulge creates a denser core? Yousuf Khan |
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