8 February 2017 | The Seagull Nebula

The Seagull Nebula Steve and Lis Milne

Image credit & copyright: Steve and Lis Milne | Click image to enlarge

Image Data

  • Camera: Atik 11000
  • Optics: Takahashi FSQ106
  • Mount: Mesu 200
  • Filters: Astrodon Ha 3nm, Baader OIII 8.5nm, Baader RGB
  • Exposure: RGB 4 x 400 secs each, Ha 12 x 1200 secs, OIII 8 x 1200 secs

Running along the border between the constellations of Canis Major (The Great Dog) and Monoceros (The Unicorn) in the southern sky, the Seagull Nebula is a huge cloud mostly made of hydrogen gas. It’s an example of what astronomers refer to as an HII region. Hot new stars form within these clouds and their intense ultraviolet radiation causes the surrounding gas to glow brightly.

The reddish hue in this image is a telltale sign of the presence of ionised hydrogen. The Seagull Nebula, known more formally as IC 2177, is a complex object with a bird-like shape that is made up of three large clouds of gas — Sharpless 2-292 forms the “head”, Sharpless 2-296 comprises the large “wings”, and Sharpless 2-297 is a small, knotty addition to the tip of the gull’s right “wing”.

Spiral galaxies can contain thousands of HII regions, almost all of which are concentrated along their spiral arms. The Seagull Nebula lies in one of the spiral arms of the Milky Way. But this is not the case for all galaxies; while irregular galaxies do contain HII regions, these are jumbled up throughout the galaxy, and elliptical galaxies are different yet again — appearing to lack these regions altogether. The presence of HII regions indicates that active star formation is still in progress in a galaxy.

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