Thor’s Helmet – A Wolf-Rayet Bubble in Canis Major

Image Title: Thor

Copyright: Copyright ©️ 2025 Linda Thomas-Fowler

Date image was taken: February 20, 2025

Location: Dark Sky Observatory Collective
Fort Davis, TX

Data Acquisition Method: Other

If other selected: This equipment is owned by John Kasianowicz. Images acquired by myself, Eric Kaufman and Jim Bishop.

Image Description and Details: Thor's Helmet is an emission nebula in Canis Major. Though it would be easy to think it is a planetary nebula, it is a Wolf-Rayet bubble similar to the Crescent or Bubble Nebulae. It is almost 12,000 light years away and about 30 light years across.

Though evocatively names, Thor's Helmet is the astronomical perpetuation of the myth that medieval Scandinavians wore horned helmets. Even so, it's an image that we modern humans are familiar with and it's easy to see how it got its name.

This image data was acquired between February 6th and 20th, 2025 and consisted of 4h 50m of H-alpha, 6h of S-II and 6h 20m of O-III for a total of 17h 10m total integration time. The image was processed in the Foraxx Palette as it best approximated a natural look for this target while retaining the S-II data. You can find the image processing details at: https://app.astrobin.com/i/z9nmfb

Equipment Details: Telescope: Ceravolo 300mm astrograph
Filters: Astrodon
Camera: FLI ML16200
Mount: Astro-Physics 1100GTO-AE
Image acquisition software: NINA
Image processing software: PixInsight

Name: Linda Thomas-Fowler

Website or Facebook Profile: http://lindasastronomyadventures.space