Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2025 March 17
The image shows a starfield with an oval shaped
red and light-blue tinged nebula in the centre
Please see the explanation for more detailed information.

Thor's Helmet
Image Credit & Copyright: Brian Hopkins (East Coast Astronomer)

Explanation: Thor not only has his own day (Thursday), but a helmet in the heavens. Popularly called Thor's Helmet, NGC 2359 is a hat-shaped cosmic cloud with wing-like appendages. Heroically sized even for a Norse god, Thor's Helmet is about 30 light-years across. In fact, the cosmic head-covering is more like an interstellar bubble, blown by a fast wind from the bright, massive star near the bubble's centre. Known as a Wolf-Rayet star, the central star is an extremely hot giant thought to be in a brief, pre-supernova stage of evolution. NGC 2359 is located about 15,000 light-years away toward the constellation of the Great Overdog. This sharp image is a mixed cocktail of data from narrowband filters, capturing not only natural looking stars but details of the nebula's filamentary structures. The star in the centre of Thor's Helmet is expected to explode in a spectacular supernova sometime within the next few thousand years.

Tomorrow's picture: sky danger


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