The world is wrong... and I am tired
This nebula near the top left edge of the widefield Milky Way mosaic caught my eye. It looks different from most of the other nebulas, because its emissions are so strongly in the MIPS1 channel with very little or none appearing in the other two. So in my other image, it appears extremely red. For this version, I have processed it in a way that makes it easier to see by having it screen over the green and blue channels a bit.
Anyway, one thing I have been struggling with for infrared imagery is how to interpret the various bands. Is it dust? Is it gas? What kind of dust? What kind of gas? Trying to learn more about this nebula, I came across this paper which helps me understand why it's been difficult. If I've understood it correctly, the authors looked at the emissions of known objects and compared them to the WISE W3 and W4 bands to see what matches up. In particular, the W4 band is closely associated with Hα emission for certain objects like this one, and the W4 band is very close to Spitzer's MIPS1 band presented here, so I'm satisfied to say this could probably also a Hα emission nebula.
The curling, looping appearance is unfamiliar to me. I don't know if those are actual loops or if they just look like loops from here. Note that the star itself, WR102, is nearly invisible in this image.
Pale Orange: Spitzer/MIPS1 (24μm)
Green: WISE/W3 (12μm)
Blue: Spitzer/IRAC4 (8μm)
North is NOT up. It is 58.7° counter-clockwise from up.
Tags: WR102 Wolf-Rayet nebula infrared Spitzer WISE star
A somewhat wider view of the infrared Milky Way scene. This one provides greater context, but is less visually impacting. All four corners are also fuzzy looking due to data deficiency. I also had to shrink the image down by 73% (15000px wide instead of its original 20660px) for Flickr to accept the upload.
For more information, see: www.flickr.com/photos/geckzilla/30386605114/
Tags: Sagittarius WISE Spitzer GLIMPSE infrared dust gas Milky Way black hole center nuclues Sgr A* Sagittarius A* space galaxy stars nebula
Centered on the invisible black hole called Sagittarius A*, infrared light from the Spitzer and WISE missions provides us a glimpse into what otherwise appears visually as a dark band in the constellation of Sagittarius. As you can see, it's a busy place bustling with star formation evidenced by glowing nebulas.
Because there is no separation between nearer and more distant structures, it's quite confusing. Imagine taking an x-ray of your body looking down from the top of your head with all your bones together on a single, flat plane. We can guess that larger structures are generally closer to us and the smaller ones are generally farther in the distance, but it's not always true, so it's best to take any interpretations about spatial positioning with a grain of salt. We know with our skeletal x-ray that our teeth are attached to our skull, but we don't have that advantage with our infrared view of the galaxy.
Still, it is tempting to make some general observations. Notice that there seems to be a lot of grayish-colored dust and gas sweeping outward from the center to the right side of the frame. Are we looking at the central part of an arm of our galaxy sweeping outward and toward us? Is the left side of the image the opposing arm receding in the other direction? Maybe. It does seem like some maps illustrating the Milky Way match up with this guess.
Some notes on the processing:
Once again I have made use of two Spitzer bands MIPS1/24μm and IRAC4/8μm for the red and blue channels, respectively. WISE's W3/12μm takes the green channel. Because the W3 and the MIPS1 data are so much less crisp than the IRAC4 data, I've used the IRAC4 data as a luminance layer in Photoshop. There's a bit of complexity in how I applied it. The green channel was also more strongly affected than the red channel.
One of the challenges of combining Spitzer and WISE data is that WISE imagery is at a much lower resolution. This causes some unsightly green glows around many of the stars. To deal with it this time I used a combination of a "Minimum" filter applied to the greenest areas. What this does is kind of shrink the spread of the star so it's more contained. Later on I also applied a channel mixer on some remaining green halos to nearly eliminate the glow. I think it worked really well without compromising the image quality in other ways too much.
Nov. 25 2016: I updated this image. Improvements should only be visible at around 100% zoom on the full size image. Overall image from lower zoom levels wasn't affected much.
Red: Spitzer/MIPS1 (24μm)
Green: WISE/W3 (12μm)
Blue: Spitzer/IRAC4 (8μm)
North is NOT up. It is around 60° counter-clockwise from up.
Tags: Sagittarius WISE Spitzer GLIMPSE infrared dust gas Milky Way black hole center nucleus Sgr A* Sagittarius A*
NGC 2170 is one of those nebulas which, in visible light, is difficult to forget. So striking are these tendrils of dust once they are fully revealed, one cannot help associating some kind of emotion with it. I personally find it to be dark and brooding.
These dusty star-forming regions tend to also be interesting in infrared, so I decided to see what kind of data was available in the archives. Lo and behold, Spitzer had observed the region in my favorite bands and so I set forth to compose this.
Unfortunately, it was a very troubled procedure. The most important channel—the 8μm one that I use to sharpen the whole image by applying it as a luminosity layer—was terrible. It was full of these blocky edges with some of the tiles having a bunch of extra light stuck in them, presumably from the zodiacal glow. Whatever it all went through (they call it a pipeline) didn't remove all that extra light, so I had to do it myself. I was moderately successful, but there are still things that aren't quite right with it.
Anyway, the bright spot in the center was also so bright that it easily saturated the detectors from both the Spitzer and the WISE telescopes. That does happen all the time, but it seemed extra annoying somehow. What this means simply is that there is a load of star formation going on in there. When looking at these particular infrared bands I find it's easier to think in terms of dust rather than stars, though. Sure, there are points of light that are stars, but it seems to me that without the dust component they'd all be oddly invisible.
Red: Spitzer/MIPS1 (24μm)
Green: WISE/W3 (12μm)
Blue: Spitzer/IRAC4 (8μm)
North is up.