In a galaxy teeming with spectacular objects, each so magnificent and cosmically grand, among the most spectacular are its superbubbles

While the searing stellar winds of single massive stars can blow a small bubble, ranging in diameter from fractions of 1pc to a few pc, the combined stellar winds and subsequent supernovae explosions of the entire OB association’s massive members expand these bubbles into a superbubble, an enormous structure with a diameter of ~100 pc. (In a typical OB association roughly one supernova per million years occurs, and this rate will remain approximately constant over 50 million years – the lifetime of the lowest mass B stars likely to become supernovae). 

As the hot and compressed bubble of material expands it ploughs into the surrounding material compressing it as well and trigging new star formation at the edges of the superbubble. So while destructive forces shaped the superbubble, new stars are forming around the edges where the gas is being compressed. Like recycling on a cosmic scale, this next generation of stars will breathe fresh life into the supperbubble. Such is the power of superbubbles that if they are large enough they can blow through the entire galactic disk, releasing their energy into the surrounding galactic halo or even into the intergalactic medium.

The Cloud very generously provides us with sixteen of these exotic objects and from the sheer opulence of N11 to the phantom glow of N185… no two are alike except in their ability to enchant and fascinate. A couple of them (N11 and N44) are like looking at textbook examples of the stellar birth, life and death that forms a superbubble with their vast star-filled superbubble cavities carved out by the lives and deaths of an OB association’s most massive stars, and the next generation of stars being birthed in the dollops of bright H II regions around the edges where the gas is being compressed.

In order to appreciate the astounding immensity, power, complexity and beauty of the superbubbles, one needs to first observe them at low magnification without a filter, for all, bar the extremely faint N185 and N186, are a truly beautiful sight with the glittering stars of the stellar associations powering them, and the beautiful and complex tapestry of nebulosity, glowing in varying intensity from a beautiful silky smokiness to startlingly bright.

And the radiance of these exquisite objects with a UHC filter is breath-taking – an elaborate mosaic of nebulae with every nuance of glowing nebulosity to explore – from impenetrable and brilliantly glowing knots with beautifully defined edges, to pools of swirling nebula infused with rich pearly shades and depth, to almost translucent patches whose undefined edges simply melt away into the background.

Once you have been captivated by their mystery and beauty and the sheer magnitude of what they are, these glorious superbubbles demand return trips. I find that subsequent visits are even better as a superbubble appears even more beautiful and fascinating than the memories of it burned into one’s mind. And there is always something more to see, even if it is but a strand of faint nebulosity one missed on a previous visit. Frankly, superbubbles ought to come with a warning… don’t go there, you won’t want to come back.