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Dark Halo Around Our Galaxy Looks Like Squished Beach Ball



 
 
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  #1  
Old January 8th 10, 05:02 PM posted to sci.astro,sci.physics
Yousuf Khan[_2_]
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Default 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  
Old January 8th 10, 06:42 PM posted to sci.astro,sci.physics
Autymn D. C.
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Default 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  
Old January 8th 10, 07:01 PM posted to sci.astro,sci.physics
eric gisse
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Posts: 342
Default 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  
Old January 8th 10, 11:50 PM posted to sci.astro,sci.physics
dlzc
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Posts: 1,426
Default 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  
Old January 9th 10, 04:46 PM posted to sci.astro,sci.physics
Yousuf Khan[_2_]
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Posts: 1,692
Default 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  
Old January 9th 10, 05:15 PM posted to sci.astro,sci.physics
Yousuf Khan[_2_]
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Posts: 1,692
Default 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  
Old January 9th 10, 05:34 PM posted to sci.astro
Yousuf Khan[_2_]
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Posts: 1,692
Default 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  
Old January 9th 10, 07:18 PM posted to sci.astro,sci.physics
dlzc
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Posts: 1,426
Default 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  
Old January 9th 10, 07:44 PM posted to sci.astro,sci.physics
Sam Wormley[_2_]
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Default 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  
Old January 9th 10, 08:50 PM posted to sci.astro,sci.physics
Yousuf Khan[_2_]
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Posts: 1,692
Default 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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