Two Of The Milky Way's Spiral Arms Go Missing

[drwayne]

<p id="first"><span class="date">ScienceDaily (Jun. 3, 2008)</span> &mdash; For decades, astronomers have been blind to what our galaxy, the Milky Way, really looks like. After all, we sit in the midst of it and can't step outside for a bird's eye view.</p><div>Now, new images from NASA's Spitzer Space Telescope are shedding light on the true structure of the Milky Way, revealing that it has just two major arms of stars instead of the four it was previously thought to possess.</div><p>"Spitzer has provided us with a starting point for rethinking the structure of the Milky Way," said Robert Benjamin of the University of Wisconsin, Whitewater, who presented the new results at a press conference today at the 212th meeting of the American Astronomical Society in St. Louis, Mo. "We will keep revising our picture in the same way that early explorers sailing around the globe had to keep revising their maps."</p><p>Since the 1950s, astronomers have produced maps of the Milky Way. The early models were based on radio observations of gas in the galaxy, and suggested a spiral structure with four major star-forming arms, called Norma, Scutum-Centaurus, Sagittarius and Perseus. In addition to arms, there are bands of gas and dust in the central part of the galaxy. Our sun lies near a small, partial arm called the Orion Arm, or Orion Spur, located between the Sagittarius and Perseus arms.</p><p>Rest of the story:</p><p>http://www.sciencedaily.com/releases/2008/06/080603160245.htm</p> <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>ScienceDaily (Jun. 3, 2008) &mdash; For decades, astronomers have been blind to what our galaxy, the Milky Way, really looks like. After all, we sit in the midst of it and can't step outside for a bird's eye view.Now, new images from NASA's Spitzer Space Telescope are shedding light on the true structure of the Milky Way, revealing that it has just two major arms of stars instead of the four it was previously thought to possess."Spitzer has provided us with a starting point for rethinking the structure of the Milky Way," said Robert Benjamin of the University of Wisconsin, Whitewater, who presented the new results at a press conference today at the 212th meeting of the American Astronomical Society in St. Louis, Mo. "We will keep revising our picture in the same way that early explorers sailing around the globe had to keep revising their maps."Since the 1950s, astronomers have produced maps of the Milky Way. The early models were based on radio observations of gas in the galaxy, and suggested a spiral structure with four major star-forming arms, called Norma, Scutum-Centaurus, Sagittarius and Perseus. In addition to arms, there are bands of gas and dust in the central part of the galaxy. Our sun lies near a small, partial arm called the Orion Arm, or Orion Spur, located between the Sagittarius and Perseus arms.Rest of the story:http://www.sciencedaily.com/releases/2008/06/080603160245.htm <br /> Posted by drwayne</DIV></p><p>It's a little ironic that we could know more about the overall layout of a far distant galaxy than we know about the layout of our own galaxy.&nbsp; I guess one's perspetive makes all the difference in the universe.&nbsp;&nbsp; </p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>It's a little ironic that we could know more about the overall layout of a far distant galaxy than we know about the layout of our own galaxy.&nbsp; I guess one's perspetive makes all the difference in the universe.&nbsp;&nbsp; <br /> Posted by michaelmozina</DIV></p><p>Nothing ironic at all about it.&nbsp; It's a bit hard to describe the overall structure of a house by standing in the living room.&nbsp; However, if I have access to a window to view other houses that are either complete or under construction, I can make some logical inferences about the one I'm standing in.</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[CalliArcale]

<p>Well maybe ironic isn't exactly the word, but Michael's right -- there is something intriguing about the fact that we know less about the shape of our own galaxy than about others.&nbsp; Sure, the reason's obvious.&nbsp; It's a bit like trying to see the back of your own head without using a mirror.&nbsp; But there's something intellectually amusing about it.</p> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>..Posted by drwayne</DIV></p><p>If this image is meant to depict the reconstruction from the Spitzer data, then I am rather curious about the shape of the central core.&nbsp; It would have expected something more nearly spherical.<br /></p><div id="thumbImage"><div id="thumbImage"><img style="-moz-opacity:0.1;opacity:0.1" src="http://www.sciencedaily.com/images/2008/06/080603160245-large.jpg" alt="" /></div>http://null/images/2008/06/080603160245-large.jpg</div> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>If this image is meant to depict the reconstruction from the Spitzer data, then I am rather curious about the shape of the central core.&nbsp; It would have expected something more nearly spherical. <br /> Posted by DrRocket</DIV></p><p>I believe the article mentions that the central bulge was found to be bar shaped sometime in the 90's and that 2 arms fits the profile of what is expected through observations of other galaxies.&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well maybe ironic isn't exactly the word, but Michael's right -- there is something intriguing about the fact that we know less about the shape of our own galaxy than about others.&nbsp; Sure, the reason's obvious.&nbsp; It's a bit like trying to see the back of your own head without using a mirror.&nbsp; But there's something intellectually amusing about it. <br /> Posted by CalliArcale</DIV></p><p>I can see the intellectually amusing part of it, but how do you see it as intriguing?&nbsp; It's no mystery why we can't adequately image our galaxy's structure.&nbsp;</p><p>edited to add:&nbsp; I think it's mighty impressive we've come this far.&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[yevaud]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I believe the article mentions that the central bulge was found to be bar shaped sometime in the 90's and that 2 arms fits the profile of what is expected through observations of other galaxies.&nbsp; <br /> </p><p>Posted by <em>derekmcd</em></DIV></p><p>Yes, it does sound as if the Milky Way is now being described as some flavor of Barred Spiral, such as NGC 1300 (below).</p><p><br /> <img src="http://sitelife.space.com/ver1.0/Content/images/store/11/4/8ba3c5e9-98be-41c1-942f-e9134d1a4737.Medium.jpg" alt="" /><br />&nbsp;</p> <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well maybe ironic isn't exactly the word, but Michael's right -- there is something intriguing about the fact that we know less about the shape of our own galaxy than about others.&nbsp; Sure, the reason's obvious.&nbsp; It's a bit like trying to see the back of your own head without using a mirror.&nbsp; But there's something intellectually amusing about it. <br /> Posted by CalliArcale</DIV></p><p>The term "amusing" is probably a better term alright.&nbsp; Derek is right that there are logical reasons why it's harder to see the forest for all the trees, but like you said, there is something intellectually amusing about it.&nbsp;</p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Yes, it does sound as if the Milky Way is now being described as some flavor of Barred Spiral, such as NGC 1300 (below). &nbsp; <br /> Posted by yevaud</DIV></p><p>Interestingly enough, when computer models are created to model the effect of plasmoids fired at one another in an EM field, we end up with shapes that highly resemble the shapes of galaxies. IMO that shape is directly related to the EM properties of plasma. </p>Quote from Holioscience: "On the left is a series of single frame stills from a computer animation of a cross-section through two interacting Birkeland current filaments. Not shown is the elliptical core of plasma trapped at the geometric center of the simulation. Top right is the form taken by two interacting plasmoids fired at each other across a magnetic field (courtesy of W. Bostik). Below that, side by side to show the striking correspondence between lab experiment and computer simulation in plasma cosmology, are the development of auroral instabilities as current increases from top to bottom. All images are from Physics of the Plasma Universe by Anthony Peratt.&nbsp; (Click on the image for a larger view)" <p><br /> <img src="http://sitelife.space.com/ver1.0/Content/images/store/5/10/d54b44fa-5deb-42c9-9a8b-5ecc6b663bfb.Medium.jpg" alt="" /><br />&nbsp;</p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[michaelmozina]

<p>http://plasmascience.net/tpu/downloadsCosmo/Peratt86TPS-II.pdf</p><p>FYI, Anthony Peratt has done a number of computer simulations which tend to roughly match what we observe in galaxy layouts. </p><p>&nbsp;</p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>