The corrugated galaxy: Milky Way may be much larger than previously estimated
The Milky Way galaxy is at least 50 percent larger than is commonly estimated, according to new findings that reveal that the galactic disk is contoured into several concentric ripples. The research, conducted by an international team led by Rensselaer Polytechnic Institute Professor Heidi Jo Newberg, revisits astronomical data from the Sloan Digital Sky Survey which, in 2002, established the presence of a bulging ring of stars beyond the known plane of the Milky Way.
"In essence, what we found is that the disk of the Milky Way isn't just a disk of stars in a flat plane—it's corrugated," said Heidi Newberg, professor of physics, applied physics, and astronomy in the Rensselaer School of Science. "As it radiates outward from the sun, we see at least four ripples in the disk of the Milky Way. While we can only look at part of the galaxy with this data, we assume that this pattern is going to be found throughout the disk."
Importantly, the findings show that the features previously identified as rings are actually part of the galactic disk, extending the known width of the Milky Way from 100,000 light years across to 150,000 light years, said Yan Xu, a scientist at the National Astronomical Observatories of China (which is part of the Chinese Academy of Science in Beijing), former visiting scientist at Rensselaer, and lead author of the paper.
"Going into the research, astronomers had observed that the number of Milky Way stars diminishes rapidly about 50,000 light years from the center of the galaxy, and then a ring of stars appears at about 60,000 light years from the center," said Xu. "What we see now is that this apparent ring is actually a ripple in the disk. And it may well be that there are more ripples further out which we have not yet seen."
The research, funded in part by the National Science Foundation and titled "Rings and Radial Waves in the Disk of the Milky Way," was published today in the Astrophysical Journal. Newberg, Xu, and their collaborators used data from the Sloan Digital Sky Survey (SDSS) to show an oscillating asymmetry in the main sequence star counts on either side of the galactic plane, starting from the sun and looking outward from the galactic center. In other words, when we look outward from the sun, the mid-plane of the disk is perturbed up, then down, then up, and then down again.
The new research builds upon a 2002 finding in which Newberg established the existence of the "Monoceros Ring," an "over-density" of stars at the outer edges of the galaxy that bulges above the galactic plane. At the time, Newberg noticed evidence of another over-density of stars, between the Monoceros Ring and the sun, but was unable to investigate further. With more data available from the SDSS, researchers recently returned to the mystery.
When they revisited the data, they found four anomalies: one north of the galactic plane at 2 kilo-parsecs (kpc) from the sun, one south of the plane at 4-6 kpc, a third to the north at 8-10 kpc, and evidence of a fourth to the south 12-16 kpc from the sun. The Monoceros Ring is associated with the third ripple. The researchers further found that the oscillations appear to line up with the locations of the galaxy's spiral arms. Newberg said the findings support other recent research, including a theoretical finding that a dwarf galaxy or dark matter lump passing through the Milky Way would produce a similar rippling effect. In fact, the ripples might ultimately be used to measure the lumpiness of dark matter in our galaxy.
"It's very similar to what would happen if you throw a pebble into still water - the waves will radiate out from the point of impact," said Newberg. "If a dwarf galaxy goes through the disk, it would gravitationally pull the disk up as it comes in, and pull the disk down as it goes through, and this will set up a wave pattern that propagates outward. If you view this in the context of other research that's emerged in the past two to three years, you start to see a picture is forming."
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Well now, your self there Skippy. This is a perfect example of why we aren't still waiting for a lightening bolt to start a brush fire so we can cook dinner.
A "3th" dimension?!?
This bit, quoted FTA:
I find it kinda sad, but amusing at the same time, that they always seem to assume a "bullseye" collision, when, as everyone in the whole world knows, the odds against are --literally-- astronomical.
Further --to rely upon this unlikeliest of causatives to explain this "rippled disc" is pure folly.
Like most of you, I've always visualized the spiral arms as being big, winding pipes of stars'n'dust, with matter density greatest towards their horizontal axes --which are, in effect-- the centers of mass/gravity with respect to the spiral arm.
ctd
If the mass distribution changes, this will surely impinge on notions such as MOND and, possibly, reduce the need for 'Dark Matter'...
I'm quite shocked at my long term misunderstanding, but even more shocked that anyone ever conceived of the galactic disk as being of roughly homogenous thickness, like some kind of platter.
And, again, relying upon some supposed bullseye collision to impart the so-called oscillation of the arms above and below the plane of the galaxy also seems like quite a stretch to me --if pressed, I would guess that this observation would prolly be better explained as being relict evidence of the milky way's gravitational collapse from a more-or-less spherical mass of gas'n'dust to it's current accretion disk/spiral outgrown from that gravitational collapse. There is no reason to believe that the process would have been completely uniform, and it seems natural enough --at least to me-- that some of the arms would wind in from above- and some from below- the galactic plane.
I think most science articles should probably end after "this is what we found" and just eliminate "this is what we think it means".
We can, sort of. Send an observatory to 500 AU. Use Sol as a gravitational lens. Many things will be revealed.
If we dont draw conclusions from data like you say, never.
In fact we'd have never discovered anything. How is science supposed to work to you?
Or expansion out TO a spherical shape...
It's still just a backwater suburb...
I'm not sure how people tend to to think the ripples will be symmetric with the collisions. Even off-centric collisions will give a mass center oriented ripple, like in a drum skin. Here it is the balance between gravitation, rotational momentum and the friction processes that has made the disk collapse in the first place. The null scenario of no collision is a perfectly flat disk.
I am also not sure how people construe probes for visualization, since we already have it (incomplete as it is), these features are no guesses.
I don't think it will scale up much, but we will have to add in the ripples if we want to derive an "efficient disk thickness". IIRC there is a "thin disk" which is perhaps 1000 lyrs thick, and a thicker, less dense "thick disc" that extends roughly 10 times that. [But look it up!]
Modified Newtonian gravity (MOND) is the observed feature of Elliptical galaxies which contain most of the stars in the universe (60-70%) & creates 99.9999% of all gravitational lensing because Ellipticals which create are so much more massive than Spiral galaxies. MOND also accounts for the slower rotation rates of Ellipticals at 2 km/s as cp to Spirals at 200 km/s.
Notice in all those pictures of gravitational lensing effects? Almost all those galaxies being lensed are Spirals & the galaxies creating the lensing are Ellipticals, but never the reverse. You never see pictures of Spirals lensing Ellipticals. The reason being that the gravitational fields of Spirals are so low that they cannot create lensing.
Our 'puffing up' would mean whatever was holding us flat has lost energy and the normal rules either come into effect or lose ground. And our newly discovered dwarfs, are their orbits going to be mostly circular?
http://en.wikiped...nt_sheet
;no mysterious DM or collisions needed.
What it does suggest is there are large scale electric currents/fields that go along with the large scale galactic magnetic field. The presence of those currents/fields renders the need for DM moot. No fairy dust is needed, just the proper understanding of the EM forces acting across the many scales with which they operate.
That is an interesting question and it should be possible to test it by viewing the motional behaviour of matter around the black hole. However, the bigger and more regular the tilt, the less flat our galaxy would be.
Apart from that it is known that the rapid spin of black holes causes a "wobble" by itself and this could already create ripples. Though I have no idea if such wobbles can reach out that far, I wouldn't be surprised if that is the case here.
jeez people -- we have known the MW has a thickness of about 2k light years. The NEW item in this article is that the thickness has a wave like distribution. That it get thicker in waves... we assumed a nebulous thickness before, that it was in general, that stars were densest along the plane and followed a an almost bell curve thinning the farther from the plane you traveled. This new insight is stating that the density follows a wave pattern up and down which is indeed new.
We knew it had thickness and we knew about about the 3rd dimension, what was unknown was that there was a pattern to the thickness.
you guys really don't give people with a Ph.d any type of credit on here.
Ellipticals of the size that cause gravitational lensing would of necessity need to devolve in size (lose mass) if they were to become Spirals, this because the largest Spirals are all way smaller than the more massive Ellipticals of the size that cause lensing.
Maybe smaller Ellipticals could form into Spirals but for massive Ellipticals to do this would require huge losses of mass (stars). Many Ellipticals are more than 50 times the mass of our MW, so how you go about busting up something that big to create 50 Spirals the size of the MW would require some real fireworks. It would seem only a collision with another Elliptical could provide the energy to create that manner of fireworks. Maybe someone posting here can link us to observations of colliding Ellipticals, but I'm unable to find any.
http://www.techti...xies.htm
@jediknight190501 demonstrates the purist form of goddamned sophistry. So, you would collect data and not use it? Not collect data? WTF are you trying to even say? Nothing. You just love the sound of your own voice. A number of parents on here need to have read the study about effusive praise causing narcissism. All these, "We'll I've never amounted to anything but a POS, but I've always thought...". Why would we care? Humans are the only vermin that cop an attitude.
You keep believing in fairy dust and the associated fairy tales you're told to believe and I'll continue thinking for myself. Rather than calling people names like a 8 year old child, tell us why this observation doesn't match the already observed Heliospheric current sheet in our solar system. The laws of plasma physics shows these processes are scalable, why do you choose to plant you head in the sand?
To test the origin of ripples from external perturbations run the film backwards.
If the ripples diminished from running the film backwards, the time where this occurs can highlight 'suspects' in the vicinity of the Milky Way that were there at that time.
"the film backwards" simply means a computer model (simulation) to test the initial and final parameters.
Need your added critic to the rating you gave me. Thanks.
@Dethe,
Sometimes your comments have merit, and sometimes not. However, one thing is for sure --you aren't going to win any converts to your views by quoting yourself, and any time you do --then you should expect to be downvoted, for reasons which should be obvious.
what is the medium?
is this indirect evidence of dark matter/energy ?
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