I have big plans for this region...  Every year, in fact...  Never happens... 

In testing my first Rokinon 135, I got a clear slot that allowed me to collect an hour (almost) of decent subs.  The other hour's collection were discarded, lost to high clouds.  I believe this is the last data I have for this winter of data processing, unless things clear.  The title of this "panel" in my sequencer is Barnard's Loop, Panel 8.  Yes, I hope to collect 9 panels like this one (albeit, with more time!).  In any case, I went straight to the program for Panel 8 because it contains that which interests me the most.  Yes the Loop, but also the dark clouds, reflection nebulae and other emission nebulosity.  So even though this image is starved for data, I was reasonably happy to see something.  Of course, framing for the Orion, Running Man, etc., with its dynamic range would have made it easier to get a catchy image...  But that will come later.  Right?!

Actually this image is illustrating something that I have been thinking about for some time now.  A stick in my craw, so to speak.  So often in the descriptions of what we are photographing here on AstroBin, the generic phrase "dust and gas" are thrown out there by all, even the expert astrophysicists, without any distiguishing adjectives.  As a professional doubter (scientist), this has always bothered me.  Gas and dust are two very different things.  And dust, itself has been rather poorly defined, since it seems to include just about anything that is not composed of single atoms.  I have seen precious little written that points to differential behavior or segregation of gas from dust or the mechanisms that could lead to such segregation.  To be sure, it may be rare or impossible that dust can exist in the complete absence of gas, or visa versa.  But from the many images posted here, elsewhere, and by my own examination of my images, it seems plainly obvious that there is significant segregation, at least in many locales.  And I am more convinced of this as I have perused some of the locales of my images and others using the IR capabilities displayed in Aladin.  I think one of the best examples of apparent segregation is the common occurance of bright reflection nebulae in the presence of very bright, blue (thereby also likely prodigious UV emitting) stars.  Think Pleiades.  Often, but not always, it seems that there is little associated excitation/emission associated with these.  On the other hand it is not uncommon to see to varying degrees some pink or red highlights, suggesting at least some emission is possible.  As a OSC kinda guy, I have no means to confirm Ha emissions in these cases.  In this image, I believe that the Loop is a prime example of just the opposite phenomenon.  That is we see a very strong Ha emission that comprises the Loop proper, yet the density of the material that is doing the emitting, seems quite low.  Why do I say this?  Well, it seems apparent that the bulk of the visible starfield seen here is of stars more distant than the dust and nebulosity.  One sees in the dark nebulosity an apparent severity of extinction of starlight that is dependent on the darkness/density of those dark clouds.  It may well be that the Loop here is much more distant than the apparent dark nebulosity (and even the Flame itself), but current best measurements put these features at nearly the same distances.  Fair warning, my front page image is probably not the best image to demonstrate star densities, since this image is processed for aesthetics and star-reduction has been done, selectively at that.  To counter that, I include in Revision C, the star extracted starfield, which clearly shows the extinction "lanes" left by molecular clouds, some obvious in the full image, some less obvious.  The assumption here is that the starfield is rather deep and should include stars near and far relative to our line of sight and well more distant than the nebulosity, both dark and emissive.  What is not seen is a significant stellar light extinction tied to the deep red arc of the Loop.  To be sure there is some in local areas within the Loop, but certainly does not seem to coincide with the intensity of the red emission.  Clearly extinction seems detached from the intensity of the red.  The mouseover is data overlain and registered to this field.  The data is IR imaging that come from AKARI FIS (160 uM, gray) and Herschel (160 uM, gold/purple) orbiting observatories.  These wavelengths are used as efficient means of teasing out images of molecular cloud dust.  While it is clear that dust is present throughout the field (Sorry, it takes looking at a much wider field of the data to see what no dust looks like), there lacks a strong correlation of dust structure to red emission.  Yet the Loop is said to be broadly excited to emission by stars within the distant Orion Nebula.  In any case, the rather continuous nature of the Loop suggests a common exciter, such as those stars.  To me this suggests that there is a clear separation of gas from dust.  At least on a relative basis between these vast regions.  That both can coexist, is seen in the broad cloud channel that trends directly from the Boogeyman upward in the image.  Here both dust and emission is seen though emission is muted.  And that correlation is confirmed with the IR data mouseover.  To me, whenever emission is seen coinciding with molecular clouds, the dust appears to be a strong inhibitor of gas emission within the clouds.  That may be a "duh!" conclusion, but should still be considered.  It would mean that the very bright emission nebulae we tend to stretch stongly, sometimes making them look like (and even naming them) walls, are really quite tenuous.  Only distance (and photographic methods) create the appearance of strong dense edges.  No doubt if an astronaut were to fly a ship at light speed up to one of these features, long before they reached the edge of the "wall" the brightness, and apparent density, would disappear and eventually, when crossed, the "wall" boundary would go unnoticed!   Unlike what is experienced in the movies and popular science fiction, no astronaut could ever drive their spaceship into a lake of red paint!  Consider, for those who have imaged a lot, how many times we see distant galaxies appear even through some of the brightest of emission nebulae.

I do believe that there are interesting implications of this to where we find star-forming regions.  But even though I have endless time, lacking current data, I will not go on about that!