THE THOR'S HELMET NEBULA
- NGC 2359 / Duck Nebula
- Deepsky 1665mm RGBhA
- Constellation Canis Major

NGC 2359, also known as the Duck Nebula or Thor's Helmet, is a Wolf-Rayet Ring Nebula (a special type of emission nebula) in the constellation Canis Major, south of the celestial equator. NGC 2359 has an apparent magnitude of +11.45 mag and an angular size of 9′ × 6′. It is about 15,000 light years away from the solar system and has a diameter of about 20 light years. The nebula expands at 26 kilometers per second. The mass of the bubble is estimated at 70 to 140 solar masses.
Unlike most others, this emission nebula is not caused to glow by O stars (such as the Orion Nebula) or white dwarfs (such as planetary nebulae), but by a Wolf-Rayet star: HD 56925 (WR 7, HIP 35378). This 11.4 mag bright star is located slightly west of the center of the bubble and has an effective temperature of approx. 50,000 ° Celsius. The star builds up enormous radiation pressure, which blows the outer shells into interstellar space. The matter ejected over time and propelled outwards forms a bubble that marks the shock front of the ejection.
Spectral analyses suggest that the bubble-shaped nebula is probably composed of a mixture of material lost by the central Wolf-Rayet star in an earlier ejection and the surrounding interstellar medium, which is swirled, condensed and ionized by the interaction with its strong stellar wind.



Equipment & imaging data:
Telescope: AFIL-1 - AG10 CDK F6.7 f=1665mm (remote telescope, purchased imageset)
Mount: SkyWatcher EQ8RH
Camera: FLI Proline 6303
Lights: R 6x 300s, G 7x 300s & B 8x 300s // hA 36x 900s (flats, darks, bias calibrated, dithering)
Location: Lijiang, China (Gemini Observatory), 3200m above sea level, Image Data Acquired By Alpha Zhang

Image processing:
mainly Pixinsight, additionally Photoshop, Lightroom, GraXpertAI, BTX Blur Terminator, Noise Terminator, Star X Terminator
Editing and development by me, as RGB with a touch of hAlpha mixed in.