Object of the Week, February 19th 2023 -- The Seagull Nebula

[akarsh]

Seagull Nebula
Star-Forming Region in Monoceros and Canis Major

Data
IC 2177 = Sh2-292 = LBN 1027 (Head)
HII region in Monoceros
RA: 07h 04m 26s
Dec: -10° 27'

Sh2-296 (Wings)
HII region in Monoceros
RA: 07h 05m 48s
Dec: -11° 13'

Sh2-297 = LBN 1039 (Knot at the end of a wing)
HII region in Canis Major
RA: 07h 05m 15s
Dec: -12° 20'

NGC 2327 = Ced 89B
Compact HII region in Monoceros
RA: 07h 04m 07s
Dec: -11° 19'

Bonus: NGC 2343 (Open Cluster), NGC 2335 (Open Cluster), Z CMa + Helwan 134 = HH160 (YSO)⁴.

The "Seagull Nebula" is a heavily photographed star-forming region straddling the boundary of Monoceros with Canis Major. It is estimated to lie about 3600ly away, giving it a size of about 250ly. As is typical of famously photographed nebulae, this is not an easy visual target and commands good, transparent skies and skill at discerning regions of low contrast -- just the kind of material this forum loves.

Seagull_Parts.png
Screenshot from KStars showing designations of various interesting parts of the Seagull. Imagery is from DSS2 HiPS.

History
I didn't have a lot of time to research this fascinating complex owing to a clear new moon period, so I'd encourage other forum members with any knowledge about the history or science of this object to pitch in. IC 2177, the brightest part of the Seagull Nebula which is the head/eye of the gull, was discovered photographically in 1898 by Welsh astronomer Isaac Roberts¹. Courtney Seligman¹ also points out that Roberts' paper states that "there is a wide nebulous band running across it in a south-following (southeastern) to north-preceding (northwestern) direction", which suggests that perhaps Roberts also discovered a portion of the wings of the gull (Sh2-296). In Harold Corwin's IC notes, it is mentioned that Max Wolf described a 2.5° long S-shaped nebulosity near IC 2177. Perhaps he should get credit for the discovery of most of the "Seagull Nebula". The bright knot NGC 2327 was discovered in 1785 by William Herschel and the Dreyer description reads "pretty Bright"², so those with poor skies and/or a narrow field-of-view can at least give this one a try.

Close_Up.jpg
Close up of NGC 2327 (top) and Z CMa (bottom right). DSS2/HiPS.

Science
The Seagull Nebula's sharp front suggests that perhaps it was formed by a supernova explosion. It seems that the details of its origin are unclear, although contemporary research suggests that this was shaped by not one but many supernovae. The Seagull Nebula is physically associated with the OB association "CMa OB1". From the ages of various stellar populations, there seems to have been multiple episodes of star-formation in this region. A 2019 paper³ points out that Seagull Nebula is part of an elliptical shaped bubble of nebulosity and hypothesizes that several SN explosions over the last 1--6 million years shaped this region. Supernovae send shocks through the interstellar medium, compressing them, causing star formation to occur again. Sh2-297 is apparently a site of recent star formation that may have resulted in this way. The paper hypothesizes that the Seagull Nebula glows largely from X-ray emissions generated by hot plasma created during the supernovae. The Seagull Nebula is a vista of the cycle of stellar birth and death.

CMa_Bubble.jpg
Figure from the 2019 paper³ showing the hypothesized supernova bubble that Seagull Nebula is a part of.

Night vision
With the explosion of Night Vision devices in our amateur community, the Seagull Nebula is readily experienced. Recently, in a Bortle 5 sky, someone loaned me an older 1x night vision device (of the green scintillation type) and a 15nm H-alpha filter to hold in front of it. Even with this simple NV device, the Seagull Nebula was seen in its full avian glory, barely above the noise background. In another recent session, a 4" refractor in a Bortle 4 sky fitted with a modern night vision device produced a much clearer view that looked essentially photographic.

Visual observation
But those of us who also want to experience "unprocessed" photons impinging on their own retinas like I do need not despair, for this is no Simeis 147. In two sittings over the last two months, I explored various parts of the Seagull Nebula in my 18" f/4.5, and it was "not too difficult" despite being under Bortle 4 conditions. My pandemic project on plate solving really pays off here; interfacing with a rotatable offline DSS2 (HiPS) overlay in the KStars planetarium, as I scan across the nebula, my system is able to show me on a photograph which part of the nebula I am on. I was using a 31mm Nagler equipped with a Lumicon UHC filter. My logs from the first sitting read: "Too difficult to sketch. IC 2177 is a relatively bright but not contrasty, irregular, large nebulosity around a star. The visually most contrasty part of the nebula is on the body of the gull." My rough sketch of the area shows the region between IC 2177 and NGC 2343 as the most contrasty region. This observation was made just after the 4" NV observation and the NV experience did not detract from the visual one, both of them being rewarding in their own ways. I missed Sh2-297 in the first sitting, so I went back and took a look at it the next time I had a chance. I described it as "A halo around a bright-ish star. A sharp dark nebula lies to the west and north west of the star. The dark nebula appears mottled. The bright nebula also seems to harbor some isolated dark patches to the east of the star.". Once again, I wrote "This is not the most visually contrasty part of the Seagull; that seems to be the region to SW and SE of and around the A-shaped star cluster at 07:08:07 -10:36:43 [which happens to be NGC 2343]."

Doing the research for this OOTW, I realized I haven't observed NGC 2327 yet. In addition, there is so much going on in this region that it definitely warrants a return. I am also yet to try it in 25x100 binoculars. I know I will revisit this region one way or the other, so why not join me

GIVE IT A GO AND LET US KNOW!

References
1. Courtney Seligman's website on IC2177
2. NGC/IC Project restoration effort on NGC 2327
3. Runaways and shells around the CMa OB1 association, B. Fernandes et. al., Astronomy & Astrophysics (2019)
4. Previous DSF OOTW thread on Z CMa

[wvreeven]

I have been observing this region with my 71 mm William Optics refractor and a 35 mm Pantoptic eye piece. I used an H-Beta filter to quickly explore this region from hotel Pachon which lies close to the construction site of Vera Rubin Observatory in Chile in November last year. I didn't know about the NGC designation, only about IC 2177. With a 5.7° FOV M 50 and several other nearby open clusters were visible in the same FOV.

[Clear Skies]

Here you go.

Seagull1.jpg Seagull-2.jpg

[Steve Gottlieb]

Here's an interesting tidbit -- although Sh 2-297 = Ced 90 doesn't carry a NGC or IC designation, it's one of the many visual discoveries of E.E. Barnard that were never published (otherwise, it would probably be better known!).

On the evening of October 28, 1889, Barnard was observing Comet 16P/Brooks through the 36-inch Clark refractor and simultaneously discovered the HCG 97 quintet (IC 5351, 5352, 5356, 5357, and 5359), which at the time was only 1?4° away from the comet. He published these discoveries, but not until 1906 when he was working at Yerkes Observatory.

Afterwards, he walked back to the small dome for the 12-inch refractor (his main instrument at the time) to search for comets and swept up Ced 90 at the southern end of the Seagull. He noted it in his logbook as “faint, diffused nebulous atmosphere, 2' in diameter (surrounding an 8th-magnitude star)". But searching for new comets was his passion at the time and he didn't want to take the time to determine an accurate position, so moved on in his sweeping.

[Uwe Glahn]

Can contribute a sketch of the region under very good transparency and dark skies with broadband filer and a large binocular.

sketch: 20x125, NELM 7m0+, Broadband Filter, field: 3°
IC2177.jpg
home

[Erik68]

I was observing the Seagull Nebula , with a refractor 152/760.
The 5.5nm H-beta filter is the best thing to use for this object. At 19x and 25x magnification,Sh2-296 and IC2177,can be seen with direct vision.NELM 6.5mag