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#401 AllanDystrup

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Posted 28 August 2019 - 05:45 AM

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W80: The NAN-Pelican Complex

    

    

     The dark dust lane in the Galactic plane of our Orion-Cygnus spiral arm is also known as the “Great Cygnus Rift”. This structure of dark molecular clouds harbors many regions of nebulosity with active star formation, the largest nearby H-II regions being: the W80 in Cyg OB7 including the NAN-Pelican nebulae E of Deneb (aka Sh2-117), plus the CYG-X in Cyg OB 2/9 with the Butterfly nebula around Sadr (aka Sh2-108, IC1318 and LBN234).

    

     I’ve studied and described these regions of the Milky Way previously in this thread:

    
     Tonight (2019-08-24, 00:30-03:30 Loc DST, CEST UT+2) I’m out again for a look at the “Northern Trifid-Lagoon” nebulae, but being in the neighborhood of Deneb, who can resist another wide-field view of the NAN-Pelican...   The North America (NGC 7000) and Pelican (IC 5070/67) nebulae form a single large H-II cloud in the W80 region, located at a distance of ~600 pc. The emission nebulosity in W80 is bifurcated by the dense molecular cloud L935, residing in the foreground at ~500 pc. The NAN-Pelican form the northern ionized arc of a large (partly hidden) H-I bubble, which on the southern edge includes the Cygnus Arc emission clouds: IC5068 A-B-C, just below the Pelican.

 

NAN-PELICAN.jpg
*click*

    

    

     The North America Nebula is mainly ionized by the two hot stars: HD199579 (O6V) plus J205551.3+435225 (O5V), the latter being obscured (dimmed by 9.6m) in LDN 935. A couple of beautiful open clusters are easily observed in the NAN: Collinder 428 in the foreground at the E, and the 100 Myr old NGC 6997 behind the NAN towards the W (at ~690 pc). Also, up N in the NAN, I can see the small NGC 6993 background star cloud residing in the B 352 dark nebula (“The Egg in the Birds’ Nest”), and I can just glimpse the small asterism W of the Bird’s Nest  known as NGC 6989.

    
     The ionized molecular ridge towards the S part of the NAN (the “Cygnus Wall”) is easily seen, as is another brightly ionized bow of nebula up north, SE the “Birds’ Nest”. These shock fronts must have been pushed out by expanding H-I bubbles caused by stellar winds and explosions from hot young stars, -- but I have not been able to find any information on the specific origin of these features in the NAN. -- Maybe others know?

    

NAN.jpg
*click*

 

To be continued...

     -- Allan


Edited by AllanDystrup, 28 August 2019 - 06:17 AM.

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#402 Jeff Morgan

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Posted 28 August 2019 - 05:08 PM

I had to smile at the "Little Orion" you annotated. A very helpful asterism.

 

Using star hopping from the very recognizable 62 Cygni and naming the stars after US cities I have helped people see the nebula, which is not intuitive to a beginner when viewed in a reversed or inverted manner:

 

https://www.cloudyni...-apt/?p=1829075



#403 AllanDystrup

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Posted 30 August 2019 - 02:01 AM

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   Jeff, yes, the "Little Orion" smile.gif, -- I don't know who coined the name, but it is a handy asterism for locating the "Gulf of Mexico" in the NAN. And certainly using the geography of US states and cities are helpful in this respect too (to US citizens at least... I can zoom in on New England, Florida/Louisiana, Texas/New Mexico, California/Oregon... but I think most Europeans will have difficulty telling Colorado from Nebraska in the NAN, so there...lol.gif ).

    

     

W80: The Pelican-IC5068

         

    

     The Pelican Neck is a bright ionization front with several interesting Herbig-Haro objects, such as a major elephant trunk terminating in the bipolar jet HH 555 (that one could be interesting to observe with larger aperture and/or EAA).

    

     There are many interesting dark bands and stripes of dust radiating out from the center of the W80 bubble, crossing over the IC 5068 Cygnus Arc EN clouds. I can detect this by adjusting the gain on the IIT device (though I can’t see it with the same resolution as a larger aperture and/or EAA would offer).

    

Pelican 2019-08-24.jpg
*click*

 

     -- Allan

 

PS: Btw, I've always thought the "Pelican" looks rather more like a Pteranodon
       Maybe that's just me...

 

Pteradon.jpg

 


Edited by AllanDystrup, 30 August 2019 - 02:18 AM.

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#404 AllanDystrup

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Posted 31 August 2019 - 03:18 AM

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The heart of the Swan.

     

    

     The area around gamma Cygni is without doubt one of the most impressive skyscapes in the Milky Way of the northern hemisphere; Here we’re looking up the inner edge of our Ori-Cyg spiral arm, with the 2.2m bright, luminous supergiant Sadr (F8Ib γ Cyg) blazing in a complex, intricately woven tapestry of star clouds, dark dust lanes (LDN889), glowing nebulae (IC1318 B-C) and sparkling open clusters (NGC 6910, OCL 180-178), all at a distance of roughly around 1.5 Kpc. Furthermore, the heart of the swan (γ Cyg area) is surrounded by first class sights on all sides, ranging from the Cyg-X OB2 association over IC1318A Dolphin and DWB119/111 Propeller to NGC6888 Crescent.

         
     Even with glass-only, the Sadr region is beautiful and interesting to observe with its multitude of young and hot stars in the large Cyg OB9 association,- and if you add large aperture, EAA or IIT, it is guaranteed to blow your socks off... shocked.gif 

    

    

IC1318A-B 2019-08-24.jpg
*click*

 

TBC,

     -- Allan

 

 


Edited by AllanDystrup, 31 August 2019 - 03:29 AM.

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#405 AllanDystrup

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Posted 31 August 2019 - 07:06 AM

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Hi Paul, and thank you smile.gif

    

     Those are in fact excellent questions! In live observation with an IIT device plus smartphone camera there are the following three basic parameters:

    

1) Gain (ie photon multiplication) of the IIT device; I distinguish between: low - medium- high - max.

2) ISO (ie receptor light sensitivity) of the specific camera; My camera ranges from 0-8700 ISO

3) Stacking type; Two main techniques:

     I)  averaging: exposure integration without alignment on stars

     II) true stacking: integration with continuous alignment on stars

    

     The higher the gain and the ISO, the more light amplification but at the cost of also amplifying noise. The more precise the polar alignment, the better the result with simple averaging (whereas true stacking is more forgiving).

    

     I observe grab/go with simple classic motorized mounts, so I only do a rough eyeballed polar align. My smartphone application (NightCap) only allows averaging, alas no stacking. Averaging for me is normally good enough up to 1s exposures integrated up to 60s. Note that the first 5-10s averaging dramatically improves the image; after that, it is a question of playing with the light (and thus noise) sensitivity versus the exposure time, depending on the object. Interesting, in this respect it is somewhat like live observing with glass only: it takes at least 5-10s for the image to "settle" on the retina (assuming full dark adaptation), and after that integration is a function with diminishing returns.

    

     So yes, to recap: High (meaning Gain=High) is how much I have turned up the photon gain on the IIT device. ISO=400 is a low light sensitivity setting (to reduce noise on the screen). And 60s averaging here means 60 x 1s camera exposures all integrated by the NightCap app on my iPhone.

 

Hope that makes sense,

 -- Allan


Edited by AllanDystrup, 31 August 2019 - 07:21 AM.

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#406 AllanDystrup

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Posted 31 August 2019 - 09:45 AM

Paul,

 

     The latest models of the iPhone have ISO settings from 24 - 10.000, and exposure times from 1/20.000 - 1s max; So these are also the ranges for the NightCap app on those smartphones (other smartphone models like Huawei have other ranges and other apps).

    

    You can, however, in the NightCap app activate the "Long exposure" option, which will then continue to average incoming frames (with your chosen settings of ISO and exposure time). So, -- if you for example choose ISO=2000 and Exp=½s, and then start a "Long exposure", then you can follow the continuous averaging of the object on the phone screen, and if you stop the "Long exposure" after say 30s, then you will have a 60 x ½s integrated image on the phone; This I would annotate on my image as: ½s Exp. 30s Ave, ISO 2000, Gain High

 

     I don't use computer and stacking programs in the field; -- The simple setup of real time live viewing using eyepiece + IIT + smartphone under the night sky at the telescope is precisely the attraction and charm of this kind of visual observation with the option of snapping a  "phonetography" along the way for later sharing.

 

     If you have further questions to the technique, I'll be glad to answer, but let's then move the discussion to the EAA forum (or PM, if you prefer), as this forum and thread is about observation of the deep sky objects, and not so much about the gizmos we use smile.gif

 

     -- Allan


Edited by AllanDystrup, 31 August 2019 - 11:54 AM.

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#407 AllanDystrup

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Posted 01 September 2019 - 06:25 AM

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The Dolphin and Propeller.

    

    
     The area of nebulosity around the Gamma Cygni Butterfly” nebula stretches far out, especially towards the NW and SW. The NW region is impressive, with strands and patches of emission nebulae hovering above the densely populated, in-bending Cyg-Ori spiral arm (the NE part of the Cygnus Star Cloud). There are several brighter ridges and knots in the nebulosity here, most notably IC 1318A (the “Dolphin”) and DWB11/119 (the “Propeller”).

    
     I’ve described my observation of these objects in Cyg OB9 before (see the Dolphin and Propeller), but here's my latest observation with a larger aperture and better resolution. The Propeller does look like you'd expect from its name, as does the Dolphin using glass only or low gain IIT/EAA, but at higher gain IC1318A looks definitely more like a deer or antelope gracefully taking a large leap over the NGC6910 open cluster.

    

Dolp-Prop.jpg

*click*

    

    

     In fact, the whole IC1318 A-B-C nebula complex surrounds NGC6910 in a spherical bubble, much like the Bernard’s Loop SNR surrounds the Trap in M42 and the NAN-Pelican-Cygnus Arc SNR surround hot stars in Cyg OB7, and so the IC1318 complex is seemingly also a remnant from a supernova explosion in Cyg OB9/NGC6910.

 

SNR BUBBLESCYG.jpg
*click*

 

     -- Allan


Edited by AllanDystrup, 01 September 2019 - 07:04 AM.

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#408 Jeff Morgan

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Posted 01 September 2019 - 09:59 AM

What atlas is that in Post 407? Nice depictions.



#409 AllanDystrup

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Posted 01 September 2019 - 12:20 PM

Jeff, -- my sky atlas:

    

Oculum, Interstellarum Deep Sky Atlas + Deep Sky Guide

http://www.deep-sky-atlas.com/

    

Interstellarum.jpg
*click*

    

     -- Allan


Edited by AllanDystrup, 01 September 2019 - 12:41 PM.

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#410 Organic Astrochemist

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Posted 01 September 2019 - 02:13 PM

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The Dolphin and Propeller.

    

    
     The area of nebulosity around the Gamma Cygni Butterfly” nebula stretches far out, especially towards the NW and SW. The NW region is impressive, with strands and patches of emission nebulae hovering above the densely populated, in-bending Cyg-Ori spiral arm (the NE part of the Cygnus Star Cloud). There are several brighter ridges and knots in the nebulosity here, most notably IC 1318A (the “Dolphin”) and DWB11/119 (the “Propeller”).

    
     I’ve described my observation of these objects in Cyg OB9 before (see the Dolphin and Propeller), but here's my latest observation with a larger aperture and better resolution. The Propeller does look like you'd expect from its name, as does the Dolphin using glass only or low gain IIT/EAA, but at higher gain IC1318A looks definitely more like a deer or antelope gracefully taking a large leap over the NGC6910 open cluster.

    

attachicon.gif Dolp-Prop.jpg

*click*

    

    

     In fact, the whole IC1318 A-B-C nebula complex surrounds NGC6910 in a spherical bubble, much like the Bernard’s Loop SNR surrounds the Trap in M42 and the NAN-Pelican-Cygnus Arc SNR surround hot stars in Cyg OB7, and so the IC1318 complex is seemingly also a remnant from a supernova explosion in Cyg OB9/NGC6910.

 

attachicon.gif SNR BUBBLESCYG.jpg
*click*

 

     -- Allan

Excellent post Allan, as always.

Bubbles seem to be a pretty ubiquitous structural motif in nature. I think that might making explaining their origins more difficult.

Here's a challenge for you: Sharpless 2-119 near 68 Cyg. I think you might be able to see something with your system. It seems that 68 Cyg is ionizing this HII region but probably not causing the expansion of a bubble. Coincidentally (?) the ring around 68 Cyg seems to be roughly about the same size on the sky as the veil nebula (NGC 6992 and 6960) and the NAN-Pelican-Cygnus and IC1318 complexes.

 

Congratulations on your sky atlas; it looks great.



#411 AllanDystrup

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Posted 02 September 2019 - 02:03 AM

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Bubbles...

 

     Thanks Organic Astrochemist! And yes indeed, bubbles in the widest sense are recurring structures in the fabric of our universe, from the Cosmic galaxy supercluster walls & voids, to Milky Way supershells & loops and down to Local disc bubbles & chimneys and individual Stellar SNR veils,  WR shells and Strömgren spheres.

 

     There is indeed an approximate ring-like structure of nebulosity around 68 Cyg, and it has previously been proposed to be a Strömgren sphere created and ionized by the hot O7.5 giant star; However, more recent studies have not been able to confirm a bubble origin (i.e. there's no thrown-off stellar envelope with a clear inner wind-blown cavity). Instead, as 68 Cyg is ramming into the ISM with supersonic velocity, the stellar wind pressure is creating a long, compressed bow shock ahead towards the SE, in front of a nebula depleted area with a trailing cone of swirling clumpy nebulosity. An interesting object, which I have also observed previously and described: here.

 

     When observing the NAN-Pelican complex, I normally also swing by the Sh2-119 bow shock, so here's my most recent observation of this object:

    

2019-08-24 Sh2-119.jpg

*click*

 

More bubbles in my next posts...smile.gif

     -- Allan


Edited by AllanDystrup, 02 September 2019 - 02:12 AM.

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#412 AllanDystrup

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Posted 03 September 2019 - 02:23 AM

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Bubbles in a stream
(live fast, die hard...)

    

    

     Each time I study the Crescent Nebula floating down the whitewater river of the Milky Way, I cannot help but think of the closing words of the Diamond Sutra: "So, this is how you should consider this fleeting world: like a star at dawn, a bubble in a stream / a flash of lightning in a summer cloud / a flickering lamp, a phantom, and a dream", the Buddha (*~500).

    

     Maybe it’s because we are now transiting from late summer into autumn, and there’s that chilling sense of inevitable transience combined with a lonely melancholy: “This dewdrop world --/ It may be a dewdrop, / And yet— and yet—”, Kobayashi Issa (*1763). But this serene mood makes the Crescent Nebula if anything even more beautiful: the stellar wind from the dying hot Wolf-Rayet star (WR136), puffing up and ionizing the shell of material cast off from its previous Red Giant stage.

              

2019-08-24 Crescent.jpg
*click*

    

   In this observation I also looked for the Soap Bubble (aka PN G75.5+1.7, size and position indicated above), but being a planetary nebula, this object does not respond well to my Hα filter. On the other hand, the P Cygni hypergiant (aka 34 Cyg) is easily seen blazing SE of the Crescent bubble; This ~2 kpc distant, ultra-massive (50x solar mass) luminous blue variable (LBV) is evolving towards the stage of a Wolf-Rayet star in an expanding bubble (like WR136 in the Crescent), and in just a few million years from now it is destined to explode as a type II hypernova, leaving behind yet another delicate SNR veil nebula floating down the Milky Way, this one with a black hole at the center. I’ve described this most interesting object here

    

     -- Allan


Edited by AllanDystrup, 04 September 2019 - 01:53 AM.

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#413 AllanDystrup

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Posted 04 September 2019 - 02:40 AM

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Burst Bubbles…

    

    

     So, the final stage for an ultra-massive star is: from a shell-hydrogen burning blue supergiant (BSG, like Cyg X-1 A), evolving into an unstable core-helium burning luminous blue variable (LBV, like P-Cygni) while shedding its outer layers, then on to a Wolf-Rayet star building an iron core and ionizing its surrounding dust/gas bubble (like WR136 in the Crescent), and finally to a core-collapse (type II) hypernova blasting its outer layers to shreds in a gamma-ray burst (GRB) and ending up as a tiny neutron star or black hole surrounded by a supernova remnant (SNR)  “veil nebula”.

    
     The best example of a SNR veil nebula as seen here from our solar system is of course THE Veil in Cygnus (aka the Cygnus Loop). This object is located in the foreground at ~0.5 Kpc (1500 Ly) when we’re looking up our Ori-Cyg spiral arm, just 3° S of ε Cyg. It is the shroud of a 20x solar mass supergiant star that expired ~8.000 years ago. Although relatively short lived, there are many other SNR veils still visible, slowly dissolving up on the night sky; Another one in Cygnus is the “Little Veil” nebula, which I visited recently : here.

    

    

2019-08-24 VEIL 01.jpg
2019-08-24 VEIL 02.jpg
*click

 

     -- Allan
 


Edited by AllanDystrup, 04 September 2019 - 02:47 AM.

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#414 AllanDystrup

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Posted 05 September 2019 - 07:01 AM

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The Cocoon

    

    

     It’s the start of autumn (2019-09-04, 01:30 Loc DST, CEST UT+2), as I poke my head out the back door to check the state of the night sky. The weather has changed significantly the past week, from late summer with warm air moving up from central Europe, to a low pressure now settling over the Scandinavian peninsula guiding cool north Atlantic air with thunder showers down over Denmark. All forecasts have promised overcast with possible rain, but right now the sky is clear (apart from a single cumulus dragging its feet down south), and the air is calm, cool and clean, with a high transparency (5-6/7) and a good seeing (8-9/10). The LP is fine too with the 30% / 4.7dy moon buried way down 30° below the W horizon, and with a NELM currently ~6m (SQM 20). The temperature is a comfy 12°C, the humidity is at 84% and the dewpoint is also far down at 8°C. -- This is a perfect early morning for star gazing, so I put on a kettle for tea, while I set up my IB mount with the 4” refractor in my backyard.

    

     My first target for tonight is the Cocoon (Sh2-125 EN with the IC5146 OC). I always find the star hop to the Cocoon a little tricky, as it is located in an area close to the border between Cygnus and Lacerta, devoid of stars brighter than 7-6m. With other telescopes I normally start my star hop from Deneb, and in a finder scope I then follow chains of bright stars up NE to the M39 OC. My 4” refractor is however relatively fast (@ f/6.4 focal ratio), so with a 55mm eyepiece I have a 4° FOV at ~12x magnification, and thus I don’t really need a finder on this scope. For first pointing the OTA to the start point of my star hop, I instead use a small laser pen. Tonight, M39 is seen floating beautifully up there in the wide 8½° FOV of my classic Zeiss 8x30 binocular and so, while looking through the bino, I can just gently push the OTA of the 4” refractor to place the laser beam (and thus the telescope) right on M39; Easy peasy  smile.gif.

     

    

     I’ve recently described the bubbles created by dying stars, but tonight’s “bubbly” object it at the other end of the life course of stars: the Cocoon is embedded in a long filament of dark dust and hydrogen gas clouds (B168), in which several other clusters of young stellar objects are in the process of gravitationally contracting (all age <100myr, including many pre-main sequence stars). The star cluster in the center of the Cocoon (IC5146 aka Cr470) contains the very young (100.000 yr.) hot B1V star: BD+46 3474, which has ionized part of the surrounding hydrogen cloud so it’s now glowing brightly in Hα (Sh2-125). Another interesting star in IC5146 is the Herbig Be star BD+46 3471 which has a circumstellar disc still embedded in its gas/dust envelope.

    

     The 1.5° long B168 DMC with the Cocoon stellar nursery is located up the Ori-Cyg arm only a good 1 kpc away, together with the M39 OC. B168 is broken up towards the W into two dark streamers (a northern + a southern), each consisting of several smaller dust cloud patches, which have been assigned individual LND numbers. I’ve observed the Cocoon nebula before (here), where I also discussed the possibility of star formation in the E end of the B168 DMC having been ignited by a supernova explosion in the close by Lacerta OB1 association towards the SE; If so, that would be a nice way of tying together my observations here of both the birth and death of stars: “the circle of life”...

    

2019-09-04 Cocoon.png

*click*

 

     -- Allan


Edited by AllanDystrup, 05 September 2019 - 07:30 AM.

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#415 Corcaroli78

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Posted 05 September 2019 - 03:13 PM

Hi Allan,

 

Happy to read that the observing conditions are improving in our part of the globe. You wrote a beautiful concise essay about the Veil. i hope to dedicate some time to it in a couple of weeks in Kompedal. 

 

Thanks for sharing!

 

Carlos 



#416 AllanDystrup

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Posted 07 September 2019 - 02:01 AM

Thank you, Carlos! smile.gif

 

     The weather in Scandinavia is very variable here in autumn, depending on the jet stream and the wrestling of warm central European and cold north Atlantic air masses resulting in the high- and low pressures gliding north OR south of Denmark, dragging in their fronts and cloud systems.

    

     The astronomical darkness is back now, but at the same time the higher humidity often brings haze and fog with lowered transparency, and the seasonal strong winds often hamper the seeing. But -- sometimes -- all the pieces fall into place, and we have an extraordinary calm and cool night with exceptionally steady seeing; So you have to seize those opportunities!

    

     The Veil is a splendid view, both wide field with fast scopes + IIT (as in my obs. report), but also closer up using a large aperture instrument; If you get a chance at the star party, go for a 20" or larger Dob with a OIII filter in the nose. Marvelous!

    

     -- Allan



#417 AllanDystrup

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Posted 09 September 2019 - 10:12 AM

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The Cepheus Bubble (SNR)

    

    

     The Cepheus OB2 association with >75 bright young stars is located up the Milky Way at a distance of ~0.8 kpc in the outer part of our Ori-Cyg spiral arm. Its core is a relatively old subgroup: Cep OB2a, with many evolved age 7-8 Myr massive stars, centered on NGC 7160 and with the type O9II giant HD207198 close by (ca 4° due E of Alderamin (α Cep). This subgroup is surrounded by a giant ~9° diameter IR emission ring (the Cepheus Bubble: CB) formed by a supernova explosion in the subgroup, which probably kicked out the O6 Iab supergiant runaway star λ Cephei and also triggered star formation in several H-II regions now outlining the CB. 

     
     The brightest H-II region in the CB is found around the only 3.4 Myr young subgroup: Cep OB2b, which at its core has the dense open cluster Tr37 also known as IC1396. The type M2Ia luminous supergiant μ Cephei (aka “the Garnet Star”) is a prominent member of Cep OB2a, as is the hot type 06V+09V massive double star HD206267, which is the main ionizing source for the surrounding Sh2-131 emission nebula. The hot stellar wind from HD206267 is responsible for both photo-evaporation of the many surrounding globules containing YSOs with protoplanetary accretion disks, and also for the shock fronts sculpting the nearby dark dust- and hydrogen nebulae such as IC1396 A-B (the “Elephant Trunk” pillar, with 57 known ~1 Myr young YSOs) and IC1396 N.

    

     CB.jpg
*click*

    

    

     I’m out tonight, having observed the 61 Cyg bow shock (Sh2-119) and the Cocoon star forming region (Sh2-126, B168), and, oh my how time passes! – “listen: time passes,... you can hear the dew falling... the invisible starfall...”, as Dylan Thomas wrote back then, in Under Milkwood. It’s already half past three in the morning when I decide to have a quick look at the HII nebulae associated with the Cepheus supernova bubble, before going back inside for a roll in the hay. I start with a look at the Cepheus OB-2a area with the splendid Trumpler 37 central cluster wrapped in the brightly ionized Sh2-131 emission nebula. A wonderful view, though the snapshot below is a bit out of focus and the edge correction of the 55mm Plössl is somewhat lacking... I decide to call it a night, but “I shall return” to quote general MacArthur when he fled the Philippines during WWII...

    

Sh2-131.jpg
*click*

    

     -- Allan
 

    


Edited by AllanDystrup, 09 September 2019 - 10:14 AM.

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#418 AllanDystrup

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Posted 20 September 2019 - 06:08 AM

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The Flying Bat

and other tales...

    

    

     When pointing our telescope at Cygnus, we’re looking tangentially in the direction of the incurving arc of our own ORI-CYG spiral arm, with a superposition of objects at distances from 0.5 kpc (NAN-Pelican, Veil), past 1 kpc (CYG OB4, OB7, E Cyg Rift) and 1.5 kpc (CYG OB1, OB2, OB9) and out to the ~2 kpc distant structures  (CYG OB3, OB8, W Cyg Rift). The emission nebulosity in this area shows up on the night sky in Hα as a continuous giant glowing cloud with brighter knots in a patchwork from the Tulip at η Cyg past the Butterfly at γ Cyg up to the NAN-Pelican past α Cyg (Deneb).

    

    
    Pointing the telescope from the Swan further up the Milky Way at Cepheus, we’re now aiming towards the galactic anticenter, where we first see through the outer part of our local ORI-CYG arm at 1 Kpc, with many HII objects in the Cepheus Bubble around CEP OB2 (Sh2-129 Flying Bat, OB2b/Sh2-131/IC1396 Elephant, Sh2-133, -134, -140). Just to the E of the CEP Bubble and at an equal distance of ~1 kpc we find CEP OB3 (Sh2-155 Cave) and CEP OB4 (Sh2-171/CED214 ‘Parachute’).

    
     To the E of the Cave and Parachute on the night sky, we cross the interarm gap from our local ORI-CYG Arm out to the distant PERSEUS Arm, where at ~2-3 Kpc we find the CEP OB1  (Sh2-132 Dragon/Lion, Sh2-142 Wizard), CEP OB5 (Sh2-135) and CAS-OB2 (Sh2-162 Bubble and Sh2-157 ‘Wolverine’) associations. These HII-regions in the Perseus Arm form the Cassiopeia Arc of emission nebulae together with several smaller (and more distant, at ~4-5 kpc) HII patches such as Sh2-147, -148/49, -152/53.

    
     Still further out beyond the PERSEUS arm at a whopping distance of ~9 kpc are a small pair of faint EN, seen in the background just to the SW of IC1396 (Sh2-127, -128).

     _ _ _ _ _

    

     It’s closing in on midnight here in mid-September (2019-09-19, 23:30 Local DST, CEST UT+2), and the temperature is a fresh autumn 8°C with 73% humidity and a dewpoint at 3°C. The 72% (20dy) Moon is on the rise in Taurus towards the E, so the LP tonight is down at a Sub/Urban transition with 19.3 SQM (5.7 NELM). The transparency... ahh but the transparency! – it is a horrible 2-4/7 with patches and sheets of stratus undulatus clouds drifting down from the N, leaving only temporary holes for observation. Luckily my target tonight (Cepheus) is up at a good 80° altitude close to zenith, so the clouds don’t pile up too much as is the case closer to the horizon.

    

    
     I start the night by revisiting the Cepheus Bubble close by at ~1 kpc in our own Local Arm, but this time I spend a little more time focusing and also using my better corrected 41mm PAN eyepiece. I begin with an observation of the Flying Bat nebula, just NE of IC1396 (the Elephant):

    

    

CB-01 S129 A.jpg

CB-01 S129 B.jpg
*click*

 

TBC,

     -- Allan


Edited by AllanDystrup, 20 September 2019 - 06:30 AM.

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#419 j.gardavsky

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Posted 20 September 2019 - 06:55 AM

Hello Alan,

 

and thank you for the excellent read about this area of skies.

Some of the objects you have decribed, have been the targets for my season kick-off on the 3rd September

https://www.cloudyni...a/#entry9654795

 

Clear skies,

JG


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#420 AllanDystrup

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Posted 22 September 2019 - 03:15 AM

.

CEP OB2 Bubble, CEP OB3-4 strip, CAS ARC

    

    

Thank you, JG,
     Yes, the Cygnus-Cepheus-Cassiopeia area of the autumn sky is indeed ablaze with bright OB-associations plus their surrounding reflection and emission nebulae, including patches and pillars of dense dark dust. Marvelous to observe, -- but it can be a little confusing trying to piece together a 3D image of the objects here, as I tried previously in my description. Here's an attempt to identify the main structures on a map: the Cepheus OB2 Bubble and the Cepheus OB3-4 Strip (both local at 1 kpc in our own ORI-CYG spiral arm), plus the more distant Cassiopeia Arc reaching from CAS OB5-2 down into CEP OB1 at 2-4 kpc (all in the outer PERSEUS spiral arm).

    

CEP OB Map.jpg
*click*

    

    
     I’m out this splendid autumn evening (2019-09-21, 22:00 Loc DST, CEST UT+2), in a nice cool temperature of 10°C, but also with a saturated humidity (100%) and the dewpoint around 10°C, so the transparency is reduced by haze to 3-4/7 in the lowest 20° altitude towards the horizon. Fortunately, my targets for tonight are in Cepheus, up N around 80° altitude, and here the transparency is good (5-6/7) with steady seeing (8/10) and an OK suburban LP (SQM 20 ~ NELM 6), hampered only slightly by the 51% (22dy) rising moon low in Taurus (5° alt.) towards the NE.

    
     Tonight, I’ll continue my sweep of the Cepheus OB associations with their brightest emission nebulae, starting from the nearest CEP OB2-Bubble and OB3-4 strip in our Local Arm @ 1 kpc, and then crossing the interarm gap to the CAS ARC in the outer Perseus arm @ 2-4 kpc. I’ve already described my observation of the “Flying Bat” (Sh2-129) and the “Elephant Trunk” (Sh2-131, IC1396), but for completeness, let me offer a somewhat better focused view of the IC1396 HII cloud, which is rich in star formation regions with many cometary cores and young stellar objects, especially in the A part of the Elephant Trunk pillar and in the northern (N part) ionization front bordering on the B161 DN. I try to glimpse some of the globules and YSOs that has been described in these regions, -- but I need more resolution to do that!

    

IC1396-55-6.jpg
*click*

    

     -- Allan


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#421 AllanDystrup

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Posted 22 September 2019 - 03:17 AM

.

     Here's a slightly closer up look at the Elephant Trunk:

    

IC1396-41-12.jpg
*click*

    

     -- Allan

 

 

 


Edited by AllanDystrup, 22 September 2019 - 08:21 AM.

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#422 j.gardavsky

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Posted 22 September 2019 - 08:39 AM

Thank you very much Allan!

 

Finally, I have found a friend of the astrophysics behind the faint fuzzies.

I have tried to view the Cepheus Bubble objects, and the objects in the outer eastern segment

during the last 3 - 4 years.

Now, I am through with most of them, maybe your list includes something not seen as yet.

 

Anoter little project of mine has been the Orion - Eridanus Super Bubble, but there are still some filament extensions into Taurus to observe. Been mainly in Eridanus - Orion - Monoceros.

 

It is fascinating to trace the very large ionized hydrogen structures in our Galaxy, and to trace its spiral arms.

 

Clear skies,

JG


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#423 AllanDystrup

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Posted 23 September 2019 - 03:42 AM

JG,
     Yes, astronomy today is pretty much synonymous with astrophysics, right? We have come a long way from the ancient sun/moon calendars (Stonehenge...), the medieval positional stellar recordings (Tycho...) and the 17-18 century purely descriptive optical observations of moon craters, "nebulae" and double stars (Messier, Herschel...).

    

     With the cosmological revolution (Copernicus, Newton...) we started the modern scientific attempts at understanding and modelling the origin, dynamics and evolution of energy and matter in the Universe, from the chemical elements, to hydrogen clouds and dust, over stars and planets to galaxies and superstructures like clusters and walls.

 

     Modern astronomy is very much based on recent developments in spectroscopy, photometry, gravity monitors, (LIGO), interferometry (ETH), all done with digital recordings, computer simulations etc. In one word: astrophysics! Let me quote from the description of the masters programme for the study of astrophysics at Copenhagen University: "In practice, modern astronomical research consists of a considerable amount of physics. A good understanding of physics is necessary in order to describe and understand the luminosity, density, temperature and chemical composition of the various astronomical objects and phenomena. Due to the very broad nature of the topic, astrophysicists need to master elements of multiple disciplines, from classical physics to quantum mechanics, and to be well versed in the methodology of mathematical physics".

    

     I find it puzzling how much amateur astronomy today still burns up a lot of time, comparing, judging, arguing (even collecting) equipment, and when it finally gets to observing the universe, it is still often "purely descriptive recordings of moon craters, clusters, nebulae and double stars" (Messier, Herschel...). I see this endless striving for perfection of gear and skill, both in classic glass eyepiece observation and in astrophotography, as opposed to focusing on trying to understand the spatial distribution, relations, dynamics and evolution of the objects in our Universe. 

    

     Ahh well, you got me running off on a tangent there, JG grin.gif

 

__________ ooooo OOOOO ooooo __________ 

 

Cepheus OB2 Bubble
Sh2-134, Sh2-135
at λ CEP

    

    

     So, let me continue now with my roundtrip to the Cepheus OB2-Bubble, from the Flying Bat via the IC1396/Elephant to the area SE of λ Cephei (N of a line between ζ and δ CEP); Here we find a couple of outlying hot stars in the CEP OB2a association with associated hydrogen cloud ionization and emission nebulosity: namely the type O6Iab supergiant λ CEP itself with the Sh2-134 cloud and to the SE, the O9.5V hot BD+57 2513 lighting up the Sh2-135 blister on an adjacent dark molecular cloud.

    
     Lambda CEP is a runaway star moving with a peculiar velocity of vl ~-32 km/s towards the SE, creating a bow shock in front of it. It may have been kicked out from the close by CEP OB2a association towards the NNW, or (as more recent studies suggest), it can have been ejected about 2.5 Myr ago from the Cep OB3 association towards the NNE (both OB associations are at ~1 kpc distance, as is also λ Cephei). The CEP OB3 origin seems to offer the better fit for the recorded proper motion, as it is also revealed by the bow shock location. I looked for the bow shock SW of λ CEP, -- but was not able to detect it at this low magnification (12x).

 

CEP OB2a Sh2-134-135 at Lambda CEP.jpg

*click*

 

     -- Allan


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#424 AllanDystrup

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Posted 24 September 2019 - 04:10 AM

.

The CEP 25-26 Nebula Complex.

Sh2-140 and Sh2-145

    

    

     Continuing my tour around the Cepheus OB2 Bubble, I now sweep up N from the Lambda Cepheus cloud, where I find a group of emission nebulae between 25 and 26 CEP: Sh2-140, -145 and -150; Further E from here there’s also a couple of fainter HII regions in the Bubble (which I’ll not visit in this roundtrip: Sh2-137 and Sh2-133).

    

CB Sh2-140-145.jpg

*click*

      

      

     Here's a map of the mentioned Sharpless objects in the CEP OB2 Bubble; I've indicated the probable clusters for the high velocity, massive runaway supergiant λ CEP, with the most probable origin being a recoil from a binary encounter in CEP OB3.

 

CEP OB2 Bupple Map Sh2.jpg
*click*

 

    

     -- Allan


Edited by AllanDystrup, 24 September 2019 - 06:54 AM.

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#425 AllanDystrup

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Posted 25 September 2019 - 12:36 PM

.

CEP OB3-4 STRIP
Sh2-155 (Cave), Sh2-154

    

    
     I’ll leave the CEP OB2 Bubble now, and move on to the emission nebulae in the CEP OB3-4 Strip, which are lining the outer part of our local, incurving Orion-Cygnus spiral arm. These HII regions are ionized by hot stars in the CEP OB3 (Sh2-155/154) and CEP OB4 (Sh2-171/CED214) associations, all close by at ~1 kpc distance (same as the emission nebulae in the CEP OB2 Bubble).

 

CEP OB HII Map.jpg

*click*

 

 

     Here's first a closer look at the large Cepheus molecular cloud complex to the SE of 30 CEP, which is harboring the CEP OB3 group of hot young stars with their associated HII fronts and clouds. Two of the most conspicuous emission nebulae in this area are SH2-155 (Cave Nebula) and Sh2-154:

 

CEP OB3-4 STRIP Sh2-155-154 Cave.jpg
[N up, W right, as usual...]
*click*

 

 

     -- Allan


Edited by AllanDystrup, 25 September 2019 - 12:52 PM.

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