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#426 j.gardavsky

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Posted 25 September 2019 - 01:16 PM

Hello Allan,

 

it is very nice how the Sharpless nebulae in the Cepheus - Cassiopeia area of skies map the Galaxy spiral arms!

 

Thanks,

JG


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#427 AllanDystrup

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Posted 27 September 2019 - 03:47 AM

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JG: yes indeed, the HII nebulae and their embedded OB associations nicely trace out the arms of spiral galaxies, as is well seen in our neighbors in the Local Group, notable M33 (Triangulum) and M32 (Andromeda). It is sometimes a little harder to trace out the spiral structure of our own Milky Way using these markers, partly because our solar system itself is embedded in the galaxy, but also because many supernova explosion have triggered star formation in loops and bubbles around us, such as the Gould's Belt, the Cygnus Super-Bubble (CSB) and the Cepheus Bubble, -- to mention just a few smile.gif.

    

    

     Before I move on, up the Cepheus OB3-4 Strip, I'd like to add a further note on the Sh2-155/154 region in CEP OB3, which (as described in my previous post) is divided into two subgroups:

  1. the old (~10 Myr) and faint southern CEP OB3a subgroup at Sh2-154 around LSIII +60 28 (B0III)
        
  2. the younger (~7 Myr) and brightly ionized northern “Cave Nebula” area with hot stars belonging to the CEP OB3b subgroup around HD217086 (O7V), close to the giant DMC (dark molecular cloud): Cepheus B.

     It is thought that star formation in this region has progressed sequentially by shock waves from CEP OB3b, -> up north to CEP OB3a, and -> with a third generation now forming at the ionization front in the Cave Nebula (at the Hα knot seen in the zoom-in image in my previous post, just NE of HD217961).

 

 ----- ooooo OOOOO ooooo -----

    
        

 CEP OB3-4 STRIP
Sh2-171, CED214

    
        

     Continuing up NE in the CEP OB3-4 STRIP, I now arrive at the Sh2-171/CED214 (NGC7822) Hα emission complex: an expanding shell of gas and dust created by early, hot massive stars in CEP OB4. The shell is now primarily ionized by the only ~2 Myr young stars in the Berkley 59 cluster in the CED 214 part of the complex. Berk 59 contains at least nine ionizing (type O-B3) stars, including the type O7V BD+66 1675 and the ultra-hot eclipsing binary O5.5V BD+66 1673. There are several dark clouds of cold dust and gas including pillars with photo evaporation intertwined in the N part of the CED 214 HII region. Together the ~ (tilde) shaped northern nebula with the bright southern knot reminds me of a parachute with its cargo dangling below...

 

 

CEP OB3-4 STRIP OB4 Parachute.png

*click*

 

     -- Allan


Edited by AllanDystrup, 27 September 2019 - 07:16 AM.

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#428 AllanDystrup

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Posted 27 September 2019 - 05:28 AM

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Sh2-171, CED214

Zoom-In

    

    

          Here are my zoom-in observations for the two HII emission areas in the 'Parachute':

 

Sh2-171 Zoom-In.jpg

CED-214 Zoom-In.jpg

*click*

 

     -- Allan


Edited by AllanDystrup, 27 September 2019 - 05:35 AM.

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#429 j.gardavsky

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Posted 27 September 2019 - 07:25 AM

Thank you so much Allan!

 

The Sh2-171 is exactly the area of skies I have been dissecting in September. Really fascinating.

 

Best,

JG


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#430 AllanDystrup

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Posted 30 September 2019 - 04:43 AM

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Sh2-132 (The Lion)
in CEP OB1

    

    
     Panning my small refractor now, from our Local Orion-Cygnus galaxy arm with the Cepheus OB 2-3-4 emission nebulae at 1 kpc distance (the CEP Bubble and Strip), across the galactic interarm gap to the nearest outer Perseus Spiral Arm, which is lined by OB associations, from Cepheus OB1 below Eps CEP towards the SW, up through the “Cassiopeia Arc” at 2½ kpc, past CAS OB2 to the CAS OB5 Supershell above Caph (Beta CAS) towards the NE.

     
     I start my observations of the Perseus Arm nebulae from the SW, with a look at the Sh2-132 emission cloud. This nebula consists of a large but faint outer part with a brighter knot towards the NE. The bright part is illuminated by several embedded galactic open clusters of young and massive stars in the Cepheus OB1 association (Teutsch 127, SBB 1, SBB 2). The main ionizing source for the nebula is the powerhouse HD211853 (WR153ab): a Wolf Rayet binary consisting of the WN6o primary plus a O6I supergiant companion. [LBV (Luminous Blue Variable) and WR (Wolf Rayet) stars are ultramassive type-O super giants in their final stage of evolution towards an imminent core collapse type-Ib/Ic supernova explosion. I’ve written a little about these in connection with my observation of the LBV star P-Cygni in CYG OB1].

    

     Trying to make heads or tails of the appearance/semblance of the Sh2-132 nebula is somewhat like taking a figure/ground perceptual test or a Rorschach inkblot psychological test: some see a full figure lion, others a lion’s head/mane (the bright knot), some a horse (in the dark patterns) and others a dragon. Long exposure astrophotography of the object can indeed bring out the contours of a standing lion, with the head and mane being most prominent. I can glimpse that, when I max out the gain on my IIT device; In normal observation however, only the bright part of the nebula around WR153 and the embedded OB1 clusters are conspicuous, and in my eyes, that looks more like a kneeling man than any of the other proposed interpretations...

    

 

Sh2-132 Lion I.jpg

Sh2-132 Lion II.jpg

*click*

 

     -- Allan


Edited by AllanDystrup, 30 September 2019 - 04:59 AM.

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#431 j.gardavsky

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Posted 30 September 2019 - 06:02 AM

Thank you Allan for the details in Sh2-132!

 

The big binoculars with the OIII filters don't reveal (as expected) much detail, even if the nebular glow is fairly bright.It is again the ionized Hydrogen, revealing the form of this nebula in the photos.

 

Best,

JG


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#432 AllanDystrup

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Posted 02 October 2019 - 02:28 AM

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Sh2-142 (The Wizard)
in CEP OB1

    

    

     The Wizard Nebula (Sh2-142) is an Hα emission nebula around the ~5 Myr young open cluster NGC 7380 in the CEP OB1 association. It is located together with the Lion Nebula (Sh2-132) at the SW end of the Cassiopeia Arc in the Perseus spiral arm, at ~2½ Kpc distance from our solar system. At least 11 of the OB-stars in N7380 are ionizing (i.e.. earlier than type B2), with the main ionizing star being the spectroscopic binary HD215825 that has a pair of hot type-O stars (O5.5V+O6V) in close eclipsing orbit (making it a variable star: DH Cep). Another strongly ionizing star is the type B0I supergiant: HD215806, just N of the N7380 OC.

    
     There’s a pair of ionization fronts at the edge of two lanes of dark nebulae running in a NE-SW direction through the emission cloud, giving it an overall appearance of a clamshell with scalloped rims or (with a little more imagination): of a sitting wizard with a pointed hat towards the N and limbs stretching down SW; I can glimpse the contour of the Wizard using IIT on my small 4” refractor, though it is of course nowhere near the detailed RGB+narrowband view of bright Hα arcuate clouds, rims and knots interlaced with embedded dust lanes and reflection veils, as is seen in long exposure photographic imaging of this splendid object.

    

     Still, the Wizard is a nice friend to visit in my backyard smile.gif.

    

Sh2-142 Wizard.jpg
*click*

 

     -- Allan.

 

 


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#433 alanjgreen

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Posted 02 October 2019 - 02:52 AM

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Sh2-142 (The Wizard)
in CEP OB1

     Still, the Wizard is a nice friend to visit in my backyard smile.gif.

    

attachicon.gif Sh2-142 Wizard.jpg
*click*

 

     -- Allan.

If you rotate 90 degrees clockwise then can you see the “flying horse”?

 

Only seen the wizard shape once and that was at low magnification in the Borg 107. I just see the flying horse with the 20”.

 

Alan


Edited by alanjgreen, 02 October 2019 - 02:53 AM.

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#434 AllanDystrup

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Posted 02 October 2019 - 03:45 AM

If you rotate 90 degrees clockwise then can you see the “flying horse”? Only seen the wizard shape once and that was at low magnification in the Borg 107. I just see the flying horse with the 20”.

 

     I can do that Alan (like here), and yes, I can then see your flying Pegasus!

 

     As I normally observe with my 2" astro Amici-diagonal, I do not find it hard to see the white Wizard, especially when I turn down the ISO to emphasize the dark lanes; my Wizard even holds a Palantir (N7380) in his left hand grin.gif

 

WIZARD.png

 

     -- Allan


 


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#435 AllanDystrup

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Posted 05 October 2019 - 01:27 AM

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The Hand, the Brain and the Double Bubble

    

    

     It’s the start of October, and the polar jet stream is currently meandering across northern Europe, dragging with it series of fronts with clouds and showers; Typical Danish autumn weather, and not the best for astronomical observation, -- but there are windows between the clouds where the sun can peek through in daytime and the stars can be seen at night. Such a window opened up two days ago (2019-10-01, 22:00), and also this early AM (2019-10-03 01:00 local DST, CEST UT+2), so on both nights I managed a quick observation, dodging the incoming sheets of clouds: the first night in comfortable conditions (temp. 10°, humidity 80% and dewpoint at 3°C), whereas the second night was cold and damp (temp. 5°C, humidity 100%, dewpoint 5°C). The 3-4-day moon (15-25%) was well below the W horizon on both occasions, and the seeing was medium (6/10), but the transparency was quickly changing between a horrible 1/7 to quite a good 5/7 towards zenith, in the “holes” between drifting haze and clouds.

     
     My target these nights has been the CAS OB2 association embedded in its ionized emission nebulae, and with these up in Cassiopeia currently at ~82°altitude, I was able to take full advantage of the “holes” drifting by overhead. Extending the line from α to β CAS, it is easy to first center on M52 (NGC 7654), which is a rich, 35 Myr young OC beyond the CEP OB2-3-4 associations in our Local spiral arm, but still in the foreground of the more than twice as distant CAS OB2 association. The highly energetic CAS OB2 stars are located in a rather dusty part of the Perseus spiral arm, so the extended complex of molecular clouds is lit up in a mosaic of brightly emitting HII patches.

      

CAS-OB2 01.jpg

CAS-OB2 02.jpg
*click*

    
     The largest emission nebula in this region is Sh2-157, which has the shape of a Hand (or a lobster claw). The northern part of Sh2-157 (Sh2-157a aka Sim 13, “the fingers”) is a ring nebula with the OC: Ba3 (aka Mrk50) at its center. This cluster belongs the CAS OB2 association, and its brightest member is the strongly ionizing binary HD 219460 consisting of a Wolf-Rayet star: WR 157 (WN4.5) with a type B1II bright giant companion. The southern part of Sh2-157 (Sh2-157b aka Sim 14, “the palm”) is a compact HII region in the expanding shell around Basel-3; This area is partly ionized by two B0 stars: HD219286 plus the HD219287 supergiant.

    
     Sh2-162 (N7635) contains a wind-blown bubble around the hottest O-star in the CAS OB2 association: the O6.5III giant BD+60 2522. Its powerful stellar wind has cleared out the beautiful Bubble Nebula in the larger Sh2-162 emission cloud. The small Bubble is itself located inside a larger Bubble, previously inflated by the O-star, so we’re here actually -- without trouble -- looking at a “Double Bubble”. Beautiful! (Like being treated to a double rainbow...)

    
     Sh2- 158 is a bright HII knot around the NGC 7538 OC, which includes the hot ionizing O3.5V star: TYC 4279-1463-1. It is located at the SW edge of the large but faint Hα emission cloud Sh2-161. There’s a pair of darker streaks running NW-SE across the knot, which gives it kind of a “convoluted” look, -- hence the name ”the Brain” for Sh2-158; At low-res however, it does look more like a tadpole to me. The close by - but faint - patch of emission nebulosity Sh2-159 (LBN543) is part of the same large molecular cloud as Sh2-158 and Sh2-161.

    
     Sh2-156 is a bright core, ionized by a O7 type star embedded in the surrounding dust cloud. In this respect it is rather like a smaller version of the Brain (Sh2-158), -- “the Cerebellum” maybe? Ah well...

    

     -- Allan


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#436 AllanDystrup

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Posted 05 October 2019 - 01:40 AM

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Zoom-In on the Bubble and Brain

    

    

     I close my observation with a zoom-in on the Bubble and Brain nebulae in CAS OB2 -- quite a wonderful couple in this interesting part of the Cassiopeia Arc in the Perseus Arm:

    

CAS-OB2 03.jpg
*click*

    

     -- Allan


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#437 j.gardavsky

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Posted 05 October 2019 - 03:37 AM

Thank you Allan!

 

Very interesting, also because of the Larger Bubble structure,

JG


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#438 AllanDystrup

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Posted 06 October 2019 - 03:00 AM

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The CAS OB5 Superbubble.

    

     

     It’s another fresh and cold Autumn evening, 9 PM local with some drifting haze and low cumulus, -- but calm and with good transparency in the holes. The half-Moon is just past its rendezvous with Saturn, and is now setting at ~7° altitude below the Teaspoon in Sagittarius. The LP is good at SQM 19.6 (NELM 5.8), and I’m all set up with the small 4” refractor in my suburban backyard:

    

2019-10-06 Moon-Saturn.jpg

    

     Tonight’s target is the Cassiopeia OB5 associations with its surrounding emission nebulae, as viewed live using a Hα narrowband filter + IIT on my 55 and 41mm eyepieces. The CAS OB5 is located at the NE end of the Cassiopeia Arc in the nearest outer Perseus Arm of our Milky Way galaxy.

    

     CAS OB5 is surrounded by a ~5° large HI shell (GSH 117.8+1.5-35) that has been blown out by hot stellar winds from the OB-stars combined with the merger of several old supernova bubbles in the association. Three more recent supernova remnants (SNR) can still be found inside the HI shell: Abell 85 (CTB1, LBN576), Tycho (SN1572A) and G116.5+1.1, and at the dense edges of the HI shell, star formation with associated gas ionization has been triggered in several parts of the molecular clouds, such as the regions around: Sh2 172-173-177, Sh2-168-169 and Sh2-163-164-165-166:

    

2019-10-06 CAS OB5 Superbubble 01.jpg

2019-10-06 CAS OB5 Superbubble 02.jpg
*click*

    

     To-Be-Continued...smile.gif

     -- Allan


Edited by AllanDystrup, 06 October 2019 - 03:10 AM.

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#439 AllanDystrup

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Posted 07 October 2019 - 02:48 AM

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The CAS OB5 Superbubble
Abell 85 SNR

    

    
     I start my survey of the CAS OB5 HI Shell with a look at the Abell 85 supernova remnant (SNR), located well inside the shell. My “nebula hopping” around the shell takes off at Kappa CAS, from where I pan to Sh2-173-> NW to Sh2-170-> S to Abell 85; The panning is quite smooth, if you have a good nebula map (like the one I created from Aladin), an equatorial mount plus a wide field eyepiece on the scope (like my 4° 55mm Plössl, with a Hα narrowband filter + IIT device on top).
    
     Abell 85 is an ~10.000-year young SNR, that shows up as a large ½° diameter disc, but it has a low surface brightness, plus it’s relatively weak in OIII and Hβ emission. It has therefore proven extremely challenging for purely visual observers, and even astro-photographers often report spending tens of hours exposure to catch a good image of the object. The SNR is however bright in radio emission (CTB-1) and also decent in Hα, where especially the southern arc of the disc (LBN 576) is obvious. I have no trouble identifying the SNR using my 4” refractor + IIT, though of course the resolution is nowhere near what you can catch in a CCD image.

    

     The other two supernova bubbles inside the HI-shell (Tycho’s “Stella Nova” from 1572:SN1572A plus G116.5+1.1) are both strong in radio and X-ray emission, but very faint in Hα, so I don’t spend time tonight paying these objects a visit; I’d be interested to know however if anyone here have caught Tycho’s “new star” with amateur instruments? Maybe I should try to see it next time I’m out with my 4” refractor.

    

CAS OB5 - Abel 85.jpg

*click*

 

     -- Allan


Edited by AllanDystrup, 07 October 2019 - 02:49 AM.

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#440 AllanDystrup

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Posted 08 October 2019 - 03:17 AM

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The CAS OB5 Superbubble
The Piggy Snout and friends

    

    

     Sh2-173 is located at the dense SE edge of the large HI shell: GSH 117.8+1.5-35. The expansion of the HI shell (5 Myr ago) into the surrounding molecular clouds has triggered the Hα emitting HII region Sh2-173 (1 Myr). The nebula has a central open cluster: Mayer 1 that includes a type O9V ionizing star BD +60 39, and the hot stellar wind from this cluster is now expanding the bright HII region, thereby igniting a third generation of young stellar objects (YSO) in the nebula. Two patches of dark molecular clouds (LDN 1282-1283) remain embedded in Sh2-173, making it look somewhat like a masquerade eye mask or, more prosaic: like a piggy snout....

    

     There is a faint extended veil of HII nebulosity surrounding the bright “Mask”, which shows several weak emission features such as the feebly ionized arc Sh2-177 N of the O9V star BD+61 105 (below κ CAS), and a couple of small pale ionized spheres around a pair of stars in an IR cluster SW of HD1239: Sh2-172.  Both of these features are barely detectable and eminently inconspicuous in my 4” refractor. Sh2-173-177-172 are grouped together as part of the same star-forming region in the large molecular cloud complex at the SE edge of the CAS OB5 HI Shell.

    

CAS OB5 Sh2-173-177-172 01.jpg

CAS OB5 Sh2-173-177-172 02.jpg

*click*

 

     -- Allan
 

 


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#441 Jeff Morgan

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Posted 08 October 2019 - 02:30 PM

I have never heard of the Pig Snout before. But looking at your image, it absolutely jumps out!


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#442 AllanDystrup

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Posted 11 October 2019 - 01:30 AM

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Sh2-170, The Little Rosette.

    

    

     Moving from the Pig Snout (Sh2-173) up NW, I now encounter the Little Rosette Nebula (Sh2-170), which is just below CED214 in the Parachute (Sh2-171). The Little Rosette is a relatively bright (in Hα), almost circular diffuse HII region with a size ~2/3 the diameter of the full moon.

    

     It is lit up by the central young OC Stock 18, that contains two hot type-O stars: the O8V star BD+63 2093 plus the O9.5V star LSI+64 11. The stellar wind from the ionizing stars have blown out a central cavity in the molecular cloud, that shows circular ionized arcs/fronts with a few radially extending dust pillars (such as the SE Elephant Trunk). This morphology is very much like that exhibited by the (Large) Rosette Nebula (Sh2-175) in Monoceros, -- though on a smaller scale of course. An interesting object!

 

CAS OB5 Sh2-170 Little Rosette 01.jpg

CAS OB5 Sh2-170 Little Rosette 02.jpg

*click*

 

     -- Allan


Edited by AllanDystrup, 11 October 2019 - 01:32 AM.

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#443 j.gardavsky

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Posted 11 October 2019 - 01:41 PM

Hello Allan,

 

and thank you for the Little Rosette in Cas Arc CAS OB5!

 

Best,

JG


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#444 AllanDystrup

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Posted 12 October 2019 - 06:13 AM

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Sh2-165

    

    

     The Sh2-165 emission nebula is located just 1° due E of 6 CAS. It shows an NE-SW elliptical structure with a relatively large cavity, blown out by the central open cluster (BDS2003 46, most prominent in IR). I can glimpse the large wind-blown cavity in the nebula, surrounding the OC that includes the main ionizing B0V star: BD +61 2494. The asymmetric ring-shape is -- at least partly -- caused by a dense dark molecular cloud to the SE of the emission nebula:

 

CAS OB5 Sh2-165.jpg

*click*

 

     -- Allan


Edited by AllanDystrup, 12 October 2019 - 06:20 AM.

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#445 AllanDystrup

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Posted 13 October 2019 - 06:59 AM

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The Moth and the Fireflies...

S163,164,166 plus S168, 169.

    

    
     Sh2-163, -164 and -166 all (probably) belong to one extended star-forming region in the molecular clouds at the outskirts beyond the SW border of the CAS OB5 super-bubble; Here we also find another star-forming region containing the close pair of emission nebulae: Sh2-168 and -169. 

    

     Sh2-163 is the largest of these emission nebulae (~20’), and it shows an extended two-winged shape, like a Moth, while the four other mentioned objects all are rather small spherical HII patches (5-10’) ionized by a single hot star in a tight central cluster, -- like Fireflies swarming around the Moth; Let’s have a closer look:
    

    
     Sh2-163 shows a “Moth”-like shape (somewhat like a smaller and fainter version of the Gamma Cygni Butterfly Nebula E of Sadr). The bipartite structure is created by a section of dark molecular clouds cutting through the emission nebula, giving the impression of a bright N wing plus a somewhat fainter S wing. Just like the nearby Sh2-165, Sh2-163 also features a central cluster ([BDS2003] 45, best seen in IR) containing a hot ionizing star: the type O9.5V LSI+60.8. The strong stellar wind from the central cluster is expanding the HII-region thereby compressing the surrounding molecular clouds. This shock front has created a bright photo-dissociation region (PDR) in an arc at the N “wing” of the nebula, containing a pair of molecular “clumps”: one at NE (A) with active star formation, plus one at NW (B), with several deeply embedded young stellar objects (YSO).

    
     Sh2-164 is a small, amorphous patch of emission nebulosity ionized by the bright B0.2III giant: LS I+59 10. It is easily seen, but shows up rather featureless in my 4” refractor.
     Sh2-166 is an equally sized (as Sh2-164) but even fainter emission nebula, with the ionizing type-O9.5V star: BD +60 2607 at its center. I didn’t study Sh2-166 this time around.

    
     Sh2-168 is a very bright roundish emission patch around the main ionizing B0V star: LSI+60 50 in the central IR cluster [BDS2003] 47. It has an interesting morphology with a luminous central region and dark molecular clouds interwoven at the NE edge. It will definitely benefit from more resolution than my 4" can muster...
     Sh2-169 is a faintly illuminated nebulosity just SE of the much brighter Sh2-168. It is ionized by the B0III giant BD+59 2786 which is easily seen, but the surrounding veil of nebulosity is hard to spot in my 4" refractor!

    

CAS OB5 Moth and Fireflies 01.jpg

CAS OB5 Moth and Fireflies 02.jpg

*click*

 

     -- Allan


Edited by AllanDystrup, 13 October 2019 - 07:12 AM.

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