Review of "Bubble-Like" Nebula in Cygnus Aug 2008
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Review of "Bubble-Like" Nebula in Cygnus Aug 2008
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August 9, 2008 Copyright 2008 Keith B Quattrocchi
. As previously noted, we believe this nebula to
be 'co-imaged" (again, pending the findings of the IAU, "discovered" would be technically less accurate, as it may be
present in a catalogue or paper we have not seen), first by Dave Jurasevich (of the Mount Wilson Observatory) on July 6, 2008 and submitted by him to the IAU on July 10, 2008. His images were
not posted at the time of our independant "discovery" (or at least, "independant imaging") of July 17, 2008. He deserves
recognition as being the first to image and submit this object (again, pending any prior submissions noted by the IAU or other
professional sources). You can learn about Dave's excellent work at www.starimager.com and about his initial images of this nebula at http://tinyurl.com/5q4qnu . As for our work, on July 17, 2008, Dr. Mel Helm noticed
an unusually symmetrical and "Bubble-Like" HII object in a wide field image he had taken (that evening) of the Crescent Nebula.
The image, shown below, was imaged at Sierra Remote Observatories. This image was an average eight separate 10 minute sub-exposures with the FLI
Microline 16803 and the Dream16” Astrograph on a Chronos HD32 mount. The
image below (Figure 1A) shows the initial image of the Crescent Nebula and the difficult to see bubble to the lower left. Figure 1B shows the object, as originally circled, by Dr. Helm. One interesting
note. When first posted we got an email from a noted planetary nebula hunter, Kent Wallace, who noticed the original image was a mirror image (Mel's images below have been properly flipped and rotated). As
with so many aspects of this "adventure", help seems to come from many places. We appreciate his email and careful observation
of Mel's orignial image. I knew I was getting a headache using that orignal image to find the exact location of
the "bubble" on "The Sky", and now I know why (what I don't know is why I didn't notice !). You can check out Kent's
work at http://www.ccastronomy.org/members_work_wallace.htm and his southern sky work at http://www.ccastronomy.org/members_work_wallace_australia.htm .
Dr. Don Goldman reviewed older images of this region and circled the area of the object, in which a faint area of definition could be seen. The resolution was poor, but it clearly required further inspection to determine whether
it was real or artifactual, and if real, whether it was already designated. Don
wondered if this might be a Wolf-Rayet star. At this point Mel and I talked further and we decided I
should attempt to image this object in order to determine whether it was real (ie, a relatively symmetrical "bubble-like"
object) and to find the objects exact location. This was accomplished using my16” RCOS at prime, with it’s
SBIG STL-6303/AOL. The initial location was obtained by matching the star pattern
of the object to Software Bisque’s “The Sky”, as shown below (Figure 3)
Figure 4 shows the first image (compilation of several 20 minute sub-exposures)
from July 29, 2008, intentionally oriented in the same direction as “The Sky” image, above.
A few calculations
were then made of the image. The image scale of my ion milled f/9 16” RCOS at prime is 0.51 arc-sec/pixel (i.e., imaging at prime f/9 with ion
milled optics, aperture of 406 mm, FL of 3654, using a STL-6303 with 9 micron pixels at 3072 x 2048, chip size of 18,4 x 27.6
mm, all binned 1x1). This yields a FOV of 17.3 x 26 arc-min. In CCDStack
the object measures with a diameter of 464 (height) x 496 (width) pixels in height, which gives an average of 480 pixels. This
calculates to the bubble size (diameter) of about 244 arc-sec, or 4.08 arc-min diameter. The area would be 13.07 arc-min squared.
A noted Astrophysicist at Fresno State University, Dr. Frederick Ringwald, recommended that we check to see if the object has a designation in two stages. The
first was to check Skyview (http://skyview.gsfc.nasa.gov/), in particular its H-alpha survey, in order to get reasonable coordinates (right ascension and declination within a few
arc seconds), and then feed these coordinates into the Simbad database (http://simbad.u-strasbg.fr/simbad/). This was then done. Although
the Ha Comp view did not show useful images, the DSS images were available and did faintly demonstrate the object, as shown
below (Figure 5)
X,Y: 147,145 -> J2000.0: 20 15 22.16 +38 02 41.9 This gave us reasonably
good coordinates: RA: 20 15 22.16 and Dec +38 02 41.9 Using this information the Simbad site was used to look
for objects with designations in this region. The map which follows (Figure 6)
is the closest map we were able to obtain, and the exact coordinates of the object are just to the right of the “X”,
designating an X-ray object which is to the left of center, but within (but not centered in) the “Bubble”. The quality of the downloaded plot is poor, but it can be gotten directly at the
site (just below image).
The actual link to the plot map is: If you click on the X-ray object, you get the image below. The bubble is faint, but it’s center is just to the right of the X-ray source. Since the FOV is 12.9 x 12.9 arc-minutes, the X-Ray source would be about 1.8 arc-minutes from the approximate
center of the “Bubble”. Note, the coordinates of the center of the
“Bubble” are 20 15 22.16, +38 02 41.9, which differ from the X-Ray
source, as noted in the plot below See Figures 7 and 8 (image blown up), below.
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