Object of the Week February 09, 2020 - WR bubble Sharpless 2-308

[Uwe Glahn]

Sh 2-308 (= LBN 1052, WR 6, RCW 11)

WR nebula in CMa

RA: 06 54 13
DEC: -23 55 42
Size: ~35’

Deep down in CMa around 3,7' SE of Messier 41 we find one of the nicest and perfect shaped Wolf-Rayet (WR) bubble in the winter sky.

Around the very hot EZ CMa (HD 50896) we can find a full moon sized bubble. Science suspects a binary system because of the variation in brightness between 6,71 and 6,95mag. The bubble itself is emitted and ionized by UV-radiation of the hot WR star. This star is near its end and will pass away as an early supernova.
At the southern end of the bubble we can find another bright star, ο1 CMa. This 3,9mag red super giant once was supposed to be related with EZ CMa. Modern Hipparcos parallax placed the star in front (610pc) of the bubble around EZ CMa (1500pc). All in all ο1 CMa seems to associated with Collinder 121 south of Sh 2-308.

From the observable standpoint Sh 2-308 is a spectacular object. A little difficult for European observer (-24° DEC) its stands well in the North American sky. The Brightest part can be found to the east. Challenge is to see the bubble as a full circle because of its fainter SW side. Telescopes with larger fields shows the surrounded IFN. Mel Bartels could detect some brightening south and north of the nebula. Perhaps he can contribute some more information to his observation and sketch.

picture (APOD): by Laubing [N to the left]
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link to APOD (https://apod.nasa.gov/apod/ap190131.html)

sketch: Mel Bartels, 13", 55x, [OIII], SQM 21.4
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link to Mel's side (https://www.bbastrodesigns.com/drawings.html#Sh2-308)

sketch: Uwe Glahn, 14.5", 54x-83x, [OIII], NELM 7m5+
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link to the sketch (http://www.deepsky-visuell.de/Zeichnungen/Sh2-308.htm)

Give it a go and let us know.

[Ivan Maly]

Hi Uwe, I gave it a go. 20", 70x, OIII, SQM 21.5.

3794

[clive]

Did you stumble across this by accident... or did you go there on porpoise ?

[obrazell]

I could not resist - no he went there on a dolphin :-)

[Uwe Glahn]

Thanks Ivan for your constructive contribution. I could not believe, that no one else had results for that famous WR bubble so far.

@clive, Owen
porpoise, dolphin?

[obrazell]

Too far south for me to see it from the UK Uwe.

I think Clive meant purpose not porpoise but it was worth the word play.

Owen

[clive]

Owen... nope, I really did go there with the dad joke...

Down here in Australia it is known as the porpoise nebula.

[j.gardavsky]

Hello all,

I have seen this WR nebula one year ago, on the 30th March 2019:
An arc at first, then slowly worked out the ring, no structures, no surrounding nebular glows.
Not particularly faint, but also not very easy.
F/5 6" achro, Baader visual OIII (10nm) filter, eyepieces: f=25mm (Leica HC Plan S), f=11mm (Leica B40x)
Location: Backyard (nominally Bortle 4) in Erlanger Oberland

(Another object observed on that night: VMT 10 (IDSA) Monoceros Loop)

[Raul Leon]

Hi here's my observation from 2/21/2020: Sharpless 2-308 aka the Dolphin Head is a Wolf-Rayet remnant in Canis Major; size:35' ; brightest segment is the left side arc ; didn't see as much nebulosity as Mel Bartels but saw most of the bubble.I used a Lumicon OIII filter with a 31mm Nagler at 51x with my 14.5 Starstructure Dob f/4.3 at 158x 3806

[Uwe Glahn]

Wow Jiri, Sh 2-308 with a 6-inch Achro from Bortle 4 skies, thumbs up. Thanks for sharing your observation to the forum. And second wow with the observation of VMT 10, perhaps worth an own thread. Could you detect something? Funny thing, I tried this SNR two months ago together with the new discovered PN StDr 13. While I could not see the PN, I could detect some "edges" with my 27-inch and noted "perhaps an object for a widefield binocular?" :D

Thanks also for your contribution Raul. Almost the whole ring, nice result.

[Jim Chandler]

My log notes from January 28, 2017:
30" f/4.5
TeleVue Panoptic 41mm
UHC
O-III

Large, round emission nebula, a big bubble. Not seen w/o filters, seen with UHC, but better defined with the O-III. Slightly more than half of the rim of a circle seen. The brightest part showed filaments similar to the Veil. Hints of nebulosity seen in the interior of the circle, but the rim is what really shows up.

[Robin]

Hi Uwe and Jiri,

Unfortunately I cannot contribute anything here yet, because I haven't looked for Sh2-308 yet. I will definitely try! :-)

Regarding Monoceros Loop, this sounds very interesting. Frankly, I have never heard about it before. If you don't mind, I'll start a thread about it in the Off the Beaten Path subforum.. :-)

Clear skies,

Robin

[j.gardavsky]

Hello all,

why the Sh2-308 WR:
Back in the day, someone on the old astronomyforum.net has asked if I have ever seen this WR nebula.
So, this has been the starter, and expecting not much and nothing easy, I have reserved an observing session for the Sh2-308, and for the Monoceros Loop.
The Monoceros Loop goes on in another thread.

Clear skies,
Jiri

[Robin]

Hey Uwe,

I know that you are interested in faint planetary nebulae. Are you aware of this one behind (or within or in front of?) Sh2-308? It can also be seen on the photo you show above.

https://www.cloudynights.com/topic/696636-second-planetary-nebula-in-sharpless-308/

Clear skies,

Robin

[obrazell]

Well recent in that it was discovered in 2008 in the MASH II catalogue.

Owen