Mysterious MilkyWay Warp Finally Explained?

* * Beatles-Beatles writes to tell us Space.com is reporting that scientists think that a collision between mysterious 'dark matter' and two of the Milky Way's nearby neighbors may be causing our galaxy to warp 'like a vinyl record left out in the hot Sun.' From the article: 'The warp is most clearly visible in a thin disk of hydrogen gas that extends across the entire 200,000-light-year diameter of the Milky Way. Viewed sideways, one half of the hydrogen disk appears to stick up above our galaxy's plane of stars and gas, while the other half dips below the plane for a bit and then rises upward again farther away from the galaxy's center.'"

Re:How do we know our own shape?

[ackthpt]

I've always wondered, how do we know our own galaxy's shape? From our point of view. do we just look 360, more stars there, less stars here, therefore we're on the rim side of the galaxy?

In clearer areas, like high elevation or low humidity, and away from light pollution, you can practically see it with the naked eye.

But beyond that I'm sure they've whipped together a few models with super computers to demonstrate it.

Besides, our galaxy isn't warped, it's Bent!

Re:**Beatles (thread to be bitchslapped in 3..2..)

[quokkapox]

When did this bullshit start anyway? Or has it just been a slow decline. I don't remember hearing any of this back in 1999.

It would be nice if the slashdot management would engage in a little give and take to keep the community here satisfied and (as zerocool mentioned) maintain some journalistic integrity. Why NOT strive for that, other than pure laziness?

Digg is not a substitute for slashdot. You can actually learn by reading the comments here.

Re:How do we know our own shape?

[Anonymous Coward]

the galaxy's general "flat" shape is visible from the milky way being a thin line in the sky. finding out our location in the milky way is a more interesting proposition. due to the obscuring clouds of interstellar matter, we do not see the milky way being brighter on one side or the other, so it appears to be equally bright on both sides. the first indication of us being located toward the rim was the fact that the globular clusters that we observe are mostly on one side of us. when we discovered methods for measuring distances (based on the relationship between the length of a period of a type of star called the "cepheid variable" and its brightness) [first established by astronomer Leavitt], we could measure their distance from us and create a three dimensional map of the globular clusters' location in the sky. using this method, it was determined that the globular clusters are distributed with spherical symmetry about a point in the plane of the milky way (a point which was, as it happens, quite far from our own solar system). by observing that globular clusters are symmetrically distributed around the centers of other spiral galaxies (most notably the andromeda galaxy), we make the inference that our globular clusters' distribution is also centered on the center of our galaxy - and thus we determine our position relative to the center of the milky way.

well, at least that's how it went down at the beginning of the 20th century. a decade or two later when radio telescopy was developed, we were able to observe these things in a more direct fashion. but it is interesting to follow the historical development of our own location in the galaxy. :)

Blitz abstract

[mattr]

Here's the abstract for the presentation by Leo Blitz on the warp. Anyone who was at the AAS, knows someone who does or understands dark matter professionally, how about telling us if this tablecloth fluttering mentioned by Blitz in TFA might be useful as a test of dark matter? Abstract follows.

AAS 207th Meeting, 8-12 January 2006
Session 40 Galactic Structure with WIMPS, STARS and Gas
Oral, Monday, 10:00-11:30am, January 9, 2006, Salon 1

[40.05] The Shape of the HI Warp in the Outer Milky Way Disk
E.S. Levine, L. Blitz, C. Heiles (UC Berkeley), M. Weinberg (University of Massachusetts, Amherst)

Although the warping of the disk of the Milky Way has been known since 1957, our work represents the first time the Milky Way warp has been quantitatively described and we find it to be both elegant and surprising. We examine the outer Galactic HI disk for deviations from the b=0 plane by constructing maps of disk surface density, mean height, and thickness. We find that the Galactic warp is well described by a vertical offset plus two Fourier modes of frequency 1 and 2, all of which grow with Galactocentric radius. The global warp demonstrates approximately an order of magnitude more power in each mode with azimuthal wavenumber m=0,1, and 2 than in any higher frequency mode; thus three and only three modes are necessary to describe the large-scale behavior of the warp. The power in the m=0 and m=2 modes grows starting from around 15 kpc; the m=1 mode is the most powerful everywhere in the outer disk. We outline six observational conclusions regarding the warp that any potential theoretical mechanism must satisfy. We will also show a movie that demonstrates the evolution of the three modes with time.

ESL and LB are supported by NSF grant AST 02-28963. CH is supported by NSF grant AST 04-06987.

Re:missing info

[maggard]

Ignoring the dubious submitter of the story...

The Milky Way is b-i-g. The warping is not happening on a scale we'd see in our lifetimes. Indeed it likely started when the Earth was still a rock with scum problem. It'll continue long past the date the Earth is a rock with a dust problem.

Don't panic.

While dark matter (& energy), galactic distortions, and giant black holes are interesting cosmologically (and further our understanding of the universe) there's no need to start digging a hole in the back yard and buying space/time-warp-b-gone merchandise from the back of magazines.

Baloney

[quokkapox]

i suggest you look more into this matter, many things like the red shift are dependant to a degree on this, and its more voodoo than science (still.)

Boy, this thread is a trip. Parent's math is bunkum and your assertation which I directly quote above is also incorrect. Redshift has NOTHING to do with parallax measurements of distance, which can be calculated to many significant digits. Voodoo indeed. Don't believe everything you read on the internet that's modded +5, Informative...

Re:How do we know our own shape?

[barakn]

The plane of the Milky Way and the Celestial Equator do not coincide, so the Milky Way appears to the north and to the south of the Celestial Equator. Thus the Milky Way is visible from the North Pole on a clear night. Perhaps you're confusing it with the Magellanic Clouds.

What's most appalling about * * Beatles-Beatles...

[Anonymous Coward]

He has more accepted submissions for stories in the past three months than comments. Moreover most of his comments are links to other pages or just single sentences plain designed to attract moderation. I mean really, who bolds parts of sentences like that in their comments?

Some say he's not a bad guy. Not knowing I can't say.

What I can say is this - he may be a nice troll, but he's still a troll.

Re:Somebody remind me why we need Dark Matter?

[kf6auf]

Basically, we look at a galaxy and see how fast parts of it are spinning. From there, we can calculate the acceleration due to gravity on different parts of (a=v^2/r) and set this equal to the gravitational acceleration (a=GM/r^2) to find the total mass inside of whichever part we are looking at (mass outside has no net gravitational effect).

Once we have gravitationall calculated the mass distribution, we can look at normal images of the galaxy, note that we can only see 5% of that amount of mass, and declare the remaining 95% of the mass to be dark matter because we can't see it.

The current most plausible idea is that there is some other substance out there we can't see, but there are other theories involving different laws of physics, we're just not happy enough with any theory yet to abandon the others. The goal is always to make the physics fit the observations; once the observation was that the speed of light is constant, scientists concluded that there was no ether, even if they didn't understand why until 25 years later. We're just guessing that there is something we cannot see, like the way the neutrino was discovered.

Re:specifics on my subpar meat propaganda, please.

[Floody]

I believe you have misunderstood me, because of my own obscurity. I understand that the entire concept behind the spectroscope(which is what we read a 'redshift' off of), is based on the assumption that light acts much like sound (we still do not fully understand light). It goes like this. The doppler effect says that, if you are sitting in your car at a red light, and there is a huge 18 wheeler doing 75 in front and to the left of you, about to go through the green light, you will hear the sound from the 18 wheeler at a higher pitch frequency when it is coming towards you (since it is compressing the sound waves), and at a lower frequency when it has past you and it is moving away(since it is refracting the sound waves). now, the theory is, that possibly light does the same thing. a spectroscope breaks the star light through a prism and displays black lines going through one of the colors (black lines shifted through the red area = the star is moving away or black lines shifted to the blue area = the star is moving closer to us). this is not documented to be true, since we still do not fully understand the nature of light, although many people think they do. (many people say "light travels at 186 miles per second." and it seems noone knows the end to that statement to actually make it scientific. "light travels at 186 miles per second IN A VACUUM.". Noone knows exactly what light is, nor do they know that it always travels at the same speed throughout all time, space, and matter. think about the theories regarding black holes, that light can be attracted by gravity-- well, if light can be attracted by gravity, obviously the speed of light is not a constant. In 1999 Dr. Hau at Harvard slowed light down to 38 MPH, in 2000 Dallas Morning News (2/28/2000) said that some folks there slowed it down to 1MPH, then in 2001 nytimes had an article that said that scientists completely stopped light, held it in place, and then sent it out on its way.

Yeah, ok, pure psuedo-science.

(probably just a typo, but you don't really think light travels at 186 miles per second, do you?)

The acoustic doppler effect you labor on about is a simplistic model that may help the layperson grossly visualize concepts like em redshift, but it should not be assumed that a remotely similar process is at work when considering topics like stellar spectroscope shift. Audible sound represents a compression wave which propogates through a medium; electromagnetic energy does not. It can interact with matter, but it exists as a separate entity and is not a mechanical process. While field equations share some fundamental aspects with wave mechanics, this does not make them the same thing. Mathematically, there are many instances in nature where similar functions and constants are "re-used"; and generally one can simply attribute such similarities to thermodynamics (i.e. if stars were naturally square, this would violate the laws of thermodynamics).

While inter-stellar distance calculations based on stellar spectroscopy are certainly capable of being inaccurate for a number of reasons, the science behind these is based on a number of core principals wherein the speed of light is largely irrelevant for determining that the model fits (in one form or another):

1. Spectroscopy: A well studied, deterministic science with which one is capable of determining elemental components based on electromagnetic frequency distribution. The spectroscopic fingerprint is "hard"; e.g. there exist no in-between spectroscopic gradients between two elements, any more than there exist magic elements "in-between" those identified on a periodic table.

2. Red-shift occurs when an emitting object is receeding from the reference frame of an observer. This has been demonstrated experimentally and is reproducible.

3. Intersteller objects which are known to be receeding via parallax measurement exhibit redshift. Their spectroscopy

Re:How do we know our own shape?

[niktemadur]

From our point of view. do we just look 360, more stars there, less stars here, therefore we're on the rim side of the galaxy?

If it was up to visible light only, you'd be right; in fact, I believe it was William Herschel, co-discoverer of Uranus, who first attempted in the late 1700's to make a diagram of the galaxy, based exclusively on visible-light observing. As it turned out, the Milky Way seemed to have a "powder puff" shape and the sun was near the center!

However, for the better part of the last century we've been using infrared, ultraviolet, x-ray, radio, etc. If you point and shoot a picture with an infrared telescope in the direction of the Saggitarius constellation, the "loudest" source of x-rays in the night sky, the image you get is that of a central galactic bulge and a symmetrical disc that cuts across the bulge and extends outwards both left and right. This image is consistent with all observations of other spiral galaxies.