Celestial hemisphere:  Southern  ·  Constellation: Monoceros (Mon)  ·  Contains:  IC 2177  ·  NGC 2335  ·  NGC 2343
Open Clusters in the Seagull nebula, BrettWaller
Open Clusters in the Seagull nebula
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Open Clusters in the Seagull nebula

Open Clusters in the Seagull nebula, BrettWaller
Open Clusters in the Seagull nebula
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Open Clusters in the Seagull nebula

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Description

Situated on the boundary between Canis Major and Monoceros, the Seagull Nebula is a huge cloud of hydrogen gas, referred to as an HII region, with dimensions of approximately 120 x 40 minutes of arc, an area equivalent to six full Moons! Emission nebula Sh2-292 (IC 2177) constitutes the head of the "gull", while Sharpless Sh2-296 comprises the "wings", and the small, knotty appendage to the right wing tip is designated Sh2-297. Hot young stars within this cloud energize it with their intense ultraviolet radiation causing the surrounding gas to glow brightly. The distance to the Seagull Nebula is estimated to be 3750 light-years. This interesting area contains a number of fascinating objects, as described below.

The circular object at upper left is the emission nebula IC 2177, also known as Sh2-292, vdB93, Gum 1, and Ced 89c. It measures 19 x 17 minutes of arc, a diameter as large as two-thirds of a full Moon. This emission nebula is centered on HD 53367, a variable Herbig Ae/Be star of magnitude 6.96 and a mass 20 times that of our Sun, the "eye" of the gull.

The grouping of stars in the upper left-hand side of the "wing" is NGC 2335 which spans 8.7 minutes of arc and shines with a visual magnitude of 7.20, and is is also known as Collinder 127, Melotte 60, and Lund 292. It is classified as a Trumpler Type III 3 m open cluster, and lies at a distance of 4,600 light years.

The small group of stars directly below IC 2177 and beneath the left-center portion of the "wing" is NGC 2343, Stephen J. O'Meara's "Doublemint Cluster". Shining at a visual magnitude of 6.7, it spans 6 minutes of arc. The bright star to the right of the cluster, and the double star above it, also belong to this grouping (Claria, 1972), classified as a Trumpler Type II 2 pn open cluster.

The bluish reflection nebula around the bright star located just below and right of center is vdB 95, which spans 2.3 minutes of arc at a distance of 3260 light years. This faint blue reflection nebula is illuminated by the brilliant star HD 53974, a blue giant of spectral class B0III, a variable star also known as FN Canis Majoris, that pulsates with a period of 0.12 days and a range of brightness from m. 5.38 to m. 5.42. It is a massive star with estimates ranging from 19 to 36 solar masses. It is also a binary system, the primary being a magnitude 5.96 star of spectral class B0 III/IV to B2 Ia/ab. Its companion of magnitude 7.04 is separated 0.60 seconds of arc at position angle 111 degrees.

Another rather small nebula is embedded in the right-hand "wing" directly above vdB95. NGC 2327 is the bluish-white reflection nebula located in the small embayment along the top edge of the right-hand "wing". It is estimated to be at a distance of 3900 light years.

At the very tip of the right-hand wing is vdB 92, a small reflection nebula spanning 2 minutes of arc at a distance of 3160 light years. Contained within it is the small open cluster OCL 566.1, a grouping of spectral class A and B stars, the brightest of which is magnitude 8.92. A study by Soares and Bica (2003) concluded this vdB 92 is a very active region of star formation. A keen eye will note a similar region near the top edge of the image directly above vdB 92. This small reflection nebula is vdB90 (Sh2-295) and both of these reflection nebulae are energized by radiation from young B-stars contained within. The vague area of whitish nebulosity between vdB 90 and vdB 92 is LBN 1035

Two other open clusters are easily overlooked in this rich star field, and can be located at the center of the cross formed by a horizontal line between NGC 2335 and vdB95, and the vertical line from IC 2177 and NGC 2343. These two open clusters are Collinder 465 and Collinder 466. Collinder 465 has an integrated magnitude of 10.1, spans 9 minutes of arc, and contains 25+ stars; Collinder 466 has an integrated magnitude of 11.1 and spans 4 minutes of arc.

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Open Clusters in the Seagull nebula, BrettWaller