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About the image: This is a true colour image of NGC2359, also known as Thor's Helmet. It is a HII nebula comprised of ionised gases and interstellar dust. At it's center lies an extremely hot Wolf Rayet type star designated as WR7. The nebula is believed to being shaped in part by the strong stellar winds produced by this star.
The star WR7 is estimated to be 229,000 times brighter than our own sun, 13 times more massive than our sun, and 1.3 times larger. It has an estimated surface temperature of 112,200 Kelvin, that's an astonishing 111,926.85 °C. It is the second smallest Wolf Rayet star currently known.
What is a Wolf Rayet Star? A Wolf Rayet star is a rare type of star which has an unusual spectra showing prominent emission lines of ionised Helium, Nitrogen and / or carbon. Their surfaces tend to show an enhancement of heavy elements, a depletion of hydrogen and strong stellar winds. Their temperature can range from 20,000 to 250,000 Kelvin therefore making them by far some of the hottest stars in the universe. Where in the sky is it?
Thor's Helmet can be found in the constellation of Canis Major, very close to the star Sirius.