A beast with four tails

Nov 30, 2011
Barred Spiral Milky Way. Illustration Credit: R. Hurt (SSC), JPL-Caltech, NASA

(PhysOrg.com) -- The Milky Way galaxy continues to devour its small neighbouring dwarf galaxies and the evidence is spread out across the sky.

A team of astronomers led by Sergey Koposov and Vasily Belokurov of Cambridge University recently discovered two streams of stars in the Southern Galactic hemisphere that were torn off the Sagittarius dwarf galaxy. This discovery came from analysing data from the latest Sloan Digital Sky Survey (SDSS-III) and was announced in a paper released today that connects these new streams with two previously known streams in the Northern Galactic hemisphere.

"We have long known that when small dwarf galaxies fall into bigger galaxies, elongated streams, or tails, of stars are pulled out of the dwarf by the enormous tidal field," said Sergey Koposov.

An artist's impression of the four tails of the Sagittarius Dwarf Galaxy (the orange clump on the left of the image) orbiting the Milky Way. The bright yellow circle to the right of the galaxy's center is our Sun (not to scale). The Sagittarius dwarf galaxy is on the other side of the galaxy from us, but we can see its tidal tails of stars (white in this image) stretching across the sky as they wrap around our galaxy. Credit: Credit: Amanda Smith, Institute of Astronomy, University of Cambridge

The Sagittarius dwarf galaxy used to be one of the brightest of the Milky Way satellites. Its disrupted remnant now lies on the other side of the Galaxy, breaking up as it is crushed and stretched by huge tidal forces. It is so small that it has lost half of its stars and all its gas over the last billion years.

Before SDSS-III, Sagittarius was known to have two tails, one in front of and one behind the remnant. Previous SDSS imaging had already found the Sagittarius tidal tail in the Northern Galactic sky in 2006 and revealed that one of the tails was forked into two.

"That was an amazing discovery," said Vasily Belokurov, from the University's Institute of , "but the remaining piece of the puzzle, the structure in the South, was missing until now."

Sergey Koposov and colleagues analysed density maps of over 13 million stars in the latest release of Sloan Digital Sky Survey data, including the crucial coverage of the Southern Galactic sky. The new data show that the Sagittarius stream in the South is also split into two, a fatter and brighter stream alongside a thinner and fainter stream. This brighter stream is more enriched with iron and other metals than its dimmer companion. Because each generation of stars makes and distributes more metals into the next generation, the Cambridge concluded that the brighter stream is younger than the older, fainter one.

This video is not supported by your browser at this time.
This movie shows an illustration of multiple streams produced by the disruption of the Sagittarius dwarf galaxy in the Milky Way halo. The orange sphere shows the location of the Sun in the Galaxy. The Sagittarius dwarf galaxy itself is located in the middle of the stream. The size of the area shown in the movie is approximately 600 thousands light years (200 kiloparsecs). Credit: S. Koposov and the SDSS-III collaboration

"Sagittarius is like a beast with four tails," observed Wyn Evans, from the Institute of Astronomy, Cambridge University.

No one knows the mechanism that caused the splitting of the tidal tails. However, scientists believe that perhaps the Sagittarius dwarf galaxy was once a part of a binary galactic system, similar to the present day Large and Small Magellanic Clouds. Each of these could have produced a leading and trailing tail on falling into the , yielding four in all.

A map of the sky showing the numbers of stars counted in the Sagittarius streams. The colors indicate the distances to the stars identified in the study - stars located in red areas are further away, while stars in the blue areas are closer. The dotted red lines trace out the Sagittarius streams, and the blue ellipses in the center show the current location of the Sagittarius Dwarf Galaxy. Credit: S. Koposov and the SDSS-III collaboration

But co-author Geraint Lewis of Sydney University has another idea. He says "Perhaps the Sagittarius has suffered an encounter with an object in the game of Galactic billiards. Maybe a collision with a massive clump of dark matter, or even another galaxy, has split each of the streams into two."

A final theory suggests that, just as meteors have spread into different streams through evolution in the Solar system, debris from Sagittarius may have spread into different streams at different points in time. Different epochs may suffer different amounts of precession in the Galaxy, causing the split streams. "I have been running hundreds of simulations of the disruption of the Sagittarius dwarf and this idea looks very plausible," commented Jorge Penarrubia of the IAA, Granada, who was also involved in the study.

Whatever the explanation, SDSS-III has provided a wealth of new information on the engorgement of the Sagittarius galaxy. The disruption of smaller galaxies has occurred many times in the history of the Milky Way and other galaxies like ours throughout the Universe.

The wagging of the four tails of Sagittarius will shed new light on both the structure and formation of the Milky Way.

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TimESimmons
2.3 / 5 (6) Nov 30, 2011
No one knows the mechanism that caused the splitting of the tidal tails.
Quite possibly they're not splitting, they're merging. This is demonstrated here under Galaxy Simulations > Drag Spirals.

http://www.presto...ndex.htm
TimESimmons
2 / 5 (4) Nov 30, 2011
..which would account for the different composition. Otherwise v difficult to see how the tail would split and sort into old and young stars.
HannesAlfven
1.7 / 5 (6) Nov 30, 2011
How many intergalactic forks are necessary for an astrophysicist to realize that the filaments are electrical?

From "On the Critical Ionization Velocity Effect in Interstellar Space and Possible Detection of Related Continuum Emission" by Gerrit Verschuur ...

"Interstellar neutral hydrogen (HI) emission spectra manifest several families of linewidths whose numerical values (34, 13, and 6 km/s) appear to be related to the critical ionization velocities (CIVs) of the most abundant interstellar atomic species. Extended new analysis of HI emission profiles shows that the 34-km/s-wide component, which probably corresponds to the CIV for helium, is pervasive. The 34-km/s-wide linwidth family is found in low-velocity (local) HI profiles and in the so-called high-velocity clouds (HVCs). In addition, published studies of HI linewidths found in the Magellanic Stream, Very High Velocity Clouds, and Compact HVCs ..."

CIV's are what you get when you slam charged particles into neutral gas.
TimESimmons
1 / 5 (3) Nov 30, 2011
Interesting Hannes. Also when you slam neutral gas into something else? Do you have a link to the full paper?
HannesAlfven
1 / 5 (4) Nov 30, 2011
Google search on "verschuur critical ionization velocity" to pull up his papers. Verschuur typically publishes in IEEE, but some of these CIV papers have also appeared in the Astrophysical Journal.

If you look up CIV in wikipedia, it will erroneously tell you that although CIV's have been observed within the laboratory, CIV's have yet to be observed in space as well. It is only true insofar as conventional thinkers decide what to read on the basis of how much support the material confers to conventional wisdom.

Verschuur has also published a paper showing that dozens of knots within some of these filaments can be correlated with WMAP hotspots. This would seem to suggest that the CMB is not of metaphysical origins, but is instead an electromagnetic fog.

Of course, it was Fred Hoyle who stated:

"A man who falls asleep on the top of a mountain and who awakes in a fog does not think he is looking at the origin of the Universe. He thinks he is in a fog."
HannesAlfven
1 / 5 (5) Nov 30, 2011
It's also worth mentioning that there is some mystery with regards to what this HI signal at 21 cm wavelength actually is. It appears to be a change in the spin state, but why is it there? What could alter the electrical spin of an electron in such a subtle, ordered manner?

When Verschuur mapped out the interstellar matter, he found that many of these "clouds" are highly filamentary. From his book, The Invisible Universe:

"These structures are known as high-velocity clouds, although detailed maps of such features show them to be filamentary instead of cloud-like."

There is a little-known laboratory observation in plasma physics called Marklund convection which can explain these cosmic observations -- but only if we are willing to permit the hypothesis that we may be looking at PLASMAS -- not gases.

This shouldn't be all that controversial though, as most astrophysical textbooks already agree on it. From http://www.plasma...5_plasma ...

(cont'd)
HannesAlfven
1 / 5 (5) Nov 30, 2011
"Today it is recognized that 99.999% of all observable matter in the universe is in the plasma state..."[4]

"It is estimated that as much as 99.9% of the universe is comprised of plasma."[5]

"..the plasma state is the most abundant state of matter. It is thought that more than 99.9% of matter in the universe is in plasma"[6]

"plasmas are abundant in the universe. More than 99% of all known matter is in the plasma state"[7]

"It is an interesting fact that most of the material in the visible universe, as much as 99% according to some estimates, is in the plasma state"[8]

"Probably more than 99 percent of visible matter in the universe exist in the plasma state."[9]

"The plasma environment Plasmas, often called the fourth state of matter, are the most common form of matter in the universe. More than 99% of all matter"[10]

(cont'd)
HannesAlfven
1 / 5 (5) Nov 30, 2011
"It is estimated that more than 99 percent of matter in the universe exists as plasma; examples include stars, nebulae, and interstellar particles"[11]

"It is sometimes said that more than 99 percent of the material in the universe is in the form of plasma"[12]

"about 99% of matter in the universe is plasma"[13]

"99.9 percent of the Universe is made up of plasma," says Dr. Dennis Gallagher, a plasma physicist at NASA's Marshall Space Flight Center" [14]

"How was it determined that 99% of the Universe is in a plasma state? Most of the gas in interstellar space is ionized (astronomers can tell by the wavelengths of light the gas absorbs and emits), and all of the gas in stars in ionized, that's where the 99% comes from. The 99% ignores any dark matter which might be out there."[15]

Needless to say, plasmas conduct electrical currents within the laboratory. Attempts to confuse cosmic plasmas with the behavior of gases lack a solid physical foundation. It is thought-experimentation.
barakn
5 / 5 (2) Nov 30, 2011
It's also worth mentioning that there is some mystery with regards to what this HI signal at 21 cm wavelength actually is. It appears to be a change in the spin state, but why is it there? What could alter the electrical spin of an electron in such a subtle, ordered manner?
What subtle, ordered manner? One spin state is simply a higher energy than the other. A hydrogen atom can be put in that state by absorbing a photon of the right energy or via a collision. Eventually it relaxes, emitting a 21 cm photon. Wherever you have cold, hydrogen gas you will find 21 cm radiation. The fact that you find this mysterious speaks volumes about how little you actually know about physics.
HannesAlfven
1 / 5 (4) Nov 30, 2011
Re: "The fact that you find this mysterious speaks volumes about how little you actually know about physics."

There are consequences to nitpicking. It tends to lead people to ignore the bigger picture. From Gerrit Verschuur's "The Invisible Universe", p55:

"Not all is understood about the distribution of HI in the Milky Way. For example, large areas of sky are found to contain HI moving at velocities that are not expected if the gas is confined to the plane of the Galaxy. In particular, when a radio telescope is pointed above or below the galactic plane, only relatively local gas traveling at velocities between -20 km/s with respect to zero, defined in terms of the average random motion of stars near the sun, should be observed. However, HI at very high negative velocities, which indicates motion toward us, is found at high galactic latitudes ..."

(cont'd)
HannesAlfven
1.3 / 5 (4) Nov 30, 2011
"... These structures are known as high-velocity clouds, although detailed maps of such features show them to be filamentary instead of cloud-like. Their distance and origin continue to be the subject of controversy ... If an HI cloud is permeated by a magnetic field the motion of a spinning electron is altered minutely."

Critical thinkers intuitively know that the riddles of the universe will not be had by nitpicking each other, and questioning each others' intelligence. We will get at the answers by hearing out competing arguments and following the enigmas. That you choose to nitpick me and ignore the enigmas speaks volumes about your approach to science (and where it will take you). If you consistently ignore the engimas, you will always end up at conventional wisdom, regardless of how well conventional theories are performing.
HannesAlfven
1.7 / 5 (6) Nov 30, 2011
Everywhere that I look, I see a bunch of online bullies just like yourself, dismissing problems with conventional theory while simultaneously arguing against the construction of newer, more functional scientific frameworks.

Ideas which make no sense:

1. The electron has a magnetic moment and a spin, but is a point source. Really, guys? If you go back to Dirac's stated intention, he never proposed that the point-source particle was supposed to be a *physical* model. It was meant purely to perform computations, and we now treat the point-source particle idea as if it is real.

2. Electrodynamics dictates that accelerated particles emit radiation. But, none has been detected from electrons supposedly orbiting the neutrons. And if it were, the electrons would lose energy and collapse into the atom's nucleus. We are constantly told that quantum mechanics is so accurate at making predictions, and yet the ideas being proposed do not follow simple electrodynamics.
HannesAlfven
1.7 / 5 (6) Nov 30, 2011
3. Collisions between particles supposedly demonstrate something like 500 subatomic particles. And yet, we can count the number of particles which are stable on one hand. Not even the hydrogen atom is stable in the absence of another hydrogen atom, calling into question this mindless allegiance to Bohr's model. Where is the strong force which this model requires to stay stable?

4. We are told that electrons can be both a wave and a particle. But, what if there was a geometry for the electron which permitted both? There actually is: Amazingly, the simple geometry of a spinning ring would do it!

What is the point of physorg? Is it a place where bullies can pressure each other into conformity? Or, is it a place where people who like to think about the problems of science can come together and have an interesting conversation? If the people of physorg really care about science, then the critical thinkers who care about a diversity of views must stand up to the bullies be heard.
TimESimmons
1 / 5 (2) Dec 01, 2011
Thanks Hannes. Don't let them get you down. I shall do some reading.
HannesAlfven
1 / 5 (4) Dec 01, 2011
Re: "Thanks Hannes. Don't let them get you down. I shall do some reading."

I think you will find that many problems occur when we throw the baby out with the bathwater. Our minds are overwhelmed because we live in an information age. The rule of our era is information overload. The subconscious fully realizes this, and works overtime to winnow the set of ideas we feel compelled to consider down as far as possible. Without a strong philosophy to guide us -- which we lost in the 1930's -- people have devised all sorts of makeshift, simplistic mechanisms for judging ideas which have absolutely nothing to do with evaluating arguments.

What would you say if I told you that a Creationist (!) has developed a spinning ring model for the electron which appears to resolve all of the outstanding riddles of quantum mechanics, without abandoning classical physics? Would you ignore his science because of his religion? Or, would you ignore his religion?
kaasinees
1 / 5 (1) Dec 01, 2011
To me, it looks like a giant black hole consuming a giant gas cloud.
HannesAlfven
1 / 5 (4) Dec 01, 2011
I am not religious myself, and don't concern myself one bit with the religion of my theorists IF the ideas they are proposing lack a reliance upon religion. But, many people today will ignore the entirety of what somebody says based upon one tiny perceived flaw -- even as they completely ignore the flood of flaws within conventional theories.

A new, "second" scientific framework is now possible, and it is based upon electricity. At the macro-cosmic level, it is the behavior of plasmas (The Electric Universe). At the micro-cosmic scale, we have the Common Sense Science group (such as Bill Lucas) -- which picks up exactly where quantum science and electrodynamics left off, pre-Einstein. And in the middle, to deal with biology, we now have Gerald Pollack, who has proposed a new, more functional model for the operation of the cell. By combining these three theories, a second scientific framework is now possible. And it is entirely classical and unified.
Nanobanano
1 / 5 (3) Dec 03, 2011
Merger simulation shows multiple tails on several different spin axis.

http://www.youtub...V-Sv8-GQ

"sorting" stars and dust by element or age in tails is just BS.

Objects of extremely different "ages" would have to be explained as being created by different forces/sources at different times i.e. two or more different parent galaxies, or perhaps as a mis-interpretation of the physics involved.

The Earth is like 99% metal...so...does that make it "older" than the Sun?

By the logic of the article, it WOULD make the Earth older than the Sun.

===

If God made one star out of pure hydrogen, and another out of pure Iron, which one is older?

How absurd is that?

How does composition prove relative age anyway, particularly when dealing with "stable" isotopes?
jsdarkdestruction
not rated yet Dec 04, 2011
If God made one star out of pure hydrogen, and another out of pure Iron, which one is older?

How absurd is that?

you are correct, you saying that IS absurd.
i take it you must be a young earth creationist?

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