19 January 2017 | Cosmic Bubble

SH2 308 Atacama Photographic Observatory

Credit: Atacama Photographic Observatory | Click image to enlarge or here for full-size (9MB)

Image Data

  • Camera: Apogee Alta U16M
  • Optics: Takahashi TOA 150
  • Filter: Astrodon Ha and OIII 3nm
  • Exposure: 1200 minutes for Ha and 1600 minutes for OIII

Sharpless 308 (also known as Sh2-308 or S 308) is a cosmic bubble of nearly 60 light-years across, blown by the fierce winds of the huge Wolf-Rayet star HD 50896 (also known as EZ Canis Majoris) – the star near the centre of the bubble.

The windblown nebula has an age of about 70,000 years and is located some 5,200 light-years from Earth in the constellation of Canis Major, the Greater Dog.

Wolf-Rayet (WR) stars are extremely rare and short-lived super-hot stars which start their lives with dozens of times the mass of our Sun, but rapidly loose most of it through a powerful stellar wind, with speeds up to 2000 km/s. They are also highly luminous, from tens of thousands to several million times the luminosity of the Sun, although not exceptionally bright visually since most of their output is in far ultraviolet and, in the case of Sharpless 308, even in X-rays. Often occurring in binary systems, WR stars are candidates for being progenitors of long-duration Gamma Ray Bursts.

Sharpless 308 is one of only two known Wolf-Rayet bubbles that emits X-rays.

Like any good bubble, this one will eventually burst. Sharpless 308 will disperse its stellar material into the surrounding space within a few million years, to explode as a supernova.

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