Happy new year!

These wide field contains the extended structures of the spectacular Seagull complex with the Thor's Helmet as a bonus.
The picture, despite the relatively short exposure (the weather!), captured the fainter external wings of the nebula, which extend significantly beyond the "Seagull" ones, that are confined inside the Sh2-296 circle of the annotated revision B. We can say that the big picture shows that what we thought to be a Seagull is, in fact, an Albatross.

Most of the objects portrayed here are related to the Seagull Nebula and the CMa OB1 association, placed at 1000-1350 pc distance. Other few objects (Thor's Helmet and Sh2-294) are more distant, and not bound to the Seagull.
The presence in CMa OB1 of two runaway O-stars (HD 54662 and HD 57682, both visible in our picture) as well as an expanding shell of gas suggests the possibility that the structure of the Seagull region may have been shaped by a supernova explosion happened about 1 million years ago. HD 57682 may have been a companion of the massive star that exploded in the supernova, and got shot away by it!

The CMa OB1 association and its associated molecular clouds play an interesting role in the spiral structure of the Milky Way. The Orion spur, the local spiral structure, runs roughly parallel to the Perseus arm from its origin near the huge star formation region W51, and then on through Cygnus X, the second quadrant, and until it reaches CMa OB1 and the Seagull nebula. Just east of this region, it branches, with the dominant portion crossing the Perseus arm and connecting to the Outer arm. A second branch continues on in the direction of the constellation Vela and ends in the massive molecular cloud complex called the Vela molecular ridge. The Seagull nebula thus lies at a celestial river fork or street intersection and must be influenced by stellar winds, supernovae and other events originating in both branches of the Orion spur. The faint but enormous ionised clouds visible in hydrogen-alpha to the east of the CMa OB1 association hint at the structure of this enormous celestial river reaching into the outer galaxy.


Picture 1: The Orion Arm bifurcation in correspondence of Seagull Nebula. My edit of a Roberto Mura picture.

Most of the information shown here has been extracted by the magnificent site galaxymap.org.

Objects related to the Seagull Complex

Sh2-296 The Wings of the Seagull
Galactic Coordinates: (224.53°, -1.96°)
Also called RCW 1 and Gum 2, this large nebula forms the wings of the Seagull Nebula and in hydrogen-alpha can be seen to be an ionied shell surrounding the CMa OB1 star association (also sometimes identified as the CMa R1 association).
Avedisova lists 4 ionising stars for Sh 2-296, including 3 B-class stars and the O6.5V star HD 54662. (SIMBAD gives an O7III class for this star.) She places it in star formation region SFR 224.20-1.60 with other parts of the Seagull nebula.
Distance estimates are around 1100 pc.

Sh2-292 The head of the Seagull
Galactic Coordinates: (223.7°, -1.89°)
Also called RCW 2, Gum 1, vdB 93, it is both an HII region and reflection nebula (vdB 93). It is part of the CMa OB1 association and is ionized by the B0IV:e subgiant HD 53367, a young 20 solar mass star with a 5 solar mass companion in a highly elliptical orbit. Avedisova places this nebula in star formation region SFR 224.20-1.60 with other parts of the Seagull nebula.

Sh2-295
Galactic Coordinates: (224.4°, -2.75°)
A small HII region located in front of the right wing of the Seagull nebula. Avedisova says that it is ionized by three B2 V class stars: HD 52942, HD 53010 and BD -11 1761. She places it in star formation region SFR 224.20-1.60 with other parts of the Seagull nebula. However, in a 1989 paper she gives a distance estimate of about 700 parsecs, closer than the main portion of the Seagull nebula and implying that it may be a foreground object.
SIMBAD lists HD 52942 as the illuminating star for the reflection nebula vdB 90a and BD -11 1761 as the illuminating star for the reflection nebula vdB 92b, implying that the HII region surrounds several reflection nebulae.

Sh2-293
Galactic Coordinates: (224.17°, -2.87°)
Sh 2-293 is a roughly spherical nebula that appears in front of the right wing of the much larger Seagull nebula.
According to Avedisova, Sh 2-293 is ionised by the B2 III giant HD 52721. SIMBAD gives a slightly different B2Vne class for this star and identifies it as the illuminating source for the reflection nebula vdB 88, implying that Sh 2-293 may be both an HII region and reflection nebula.
Avedisova places it in star formation region SFR 224.20-1.60 with other parts of the Seagull nebula. However, in a 1989 study she places Sh 2-293 at a distance of about 750 parsecs, which is considerably closer than the other parts of the Seagull nebula, implying that it may be a foreground object.

Sh2-297 VdB94
Galactic Coordinates: (225.47°, -2.58°)
This HII region and reflection nebula is located at the tip of the right wing of the Seagull nebula. It is also known as the reflection nebula VdB94. It is located next to the cold dark nebula LDN 1657A.
Avedisova lists 5 possible ionising stars, including the O7.5 V star HD 53975, the O9.5 V star HD 54879 and the B1 II/III star HD 53623. (SIMBAD gives the class of HD 53975 as B7, too cool to be an ionizing star. SIMBAD may be incorrect, however) She places Sh 2-297 in star formation region SFR 224.20-1.60 with other parts of the Seagull nebula.

Sh2-291
Galactic Coordinates: (220.52°, -2.77°)
Avedisova associates Sh 2-291 with the carbon star EM Mon and places them both in the star formation region 220.52-2.77.
The available distance estimates place Sh 2-291 in the Cygnus (Outer) arm.
No ionizing star appears to have been identified in the scientific literature.

BFS 63
It is an Hii Region optically close to Sh2-291, a distance estimate is 930 ± 520 pc.

vdB95
It is a beautiful reflection nebula illuminated by HD 53974, a B0III blue giant, that is a variable beta Cepheid, named as well as FN Canis Majoris.

M50
It is an open cluster, recorded by G. D. Cassini before 1711 and independently discovered by Charles Messier in 1772. It is about 2,900 light-years away that places it at a similar distance of the Canis Major (CMa) OB1 association. It spans 17.8 ly The cluster has 508 confirmed and 109 probable members, it is around 140 million years old.

HD55439 Reflection Nebula
I have not found any specific classification of this beautiful reflection nebula surrounding the HD 55439 Be Star.


Picture 2: HD55439 Reflection Nebula


Distant Objects, not related to Seagull Complex

Sh2-298 NGC2359 Thor's Helmet
Galactic Coordinates: (227.75°, -0.15°)
Nicknamed Thor's Helmet, this far away nebula (500pc) is a wind blown bubble ionised by the Wolf-Rayet star WR 7 (HD 56925). To be more precise, NGC 2359 is the Wolf-Rayet nebula and this is embedded in the more diffuse Sh 2-298 Hii region.

Sh2-294 Octopus or Little Heart Nebula
Galactic Coordinates: (224.19°, 1.22°)
It has a distance of 4300 ± 1000 pc.
According to Avedisova this HII region is ionised by an uncatalogued B0.5 V star (MFJ Sh 2-294 4). It contains the loose infrared star cluster [BDS2003] 95 which is divided into two sub-clusters, the denser one surrounding the ionising star. Its odd shape looks like an upside down octopus, I see in it more a human heart.

RCW 4 The Albatross north wing
The RCW catalog identifies a large faint nebula, RCW 4, at the northern edge of the hydrogen-alpha emission surrounding the CMa OB1 association. However, no distance estimates are available and according to SIMBAD, no references in the scientific literature have ever been made to this nebula beyond the RCW catalog itself.