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Red sprites at La Silla Observatory

This unique and spectacular image of ESO’s La Silla Observatory features a cloudless sky stained with red and green airglow and bejewelled with celestial objects. Amongst the celestial cast are the Small and Large Magellanic Clouds just to the right of centre, the rosy-red glow of various star-forming regions and the faint green streak of a meteor just to the left of the Milky Way. These striking heavenly regulars are eclipsed however by the presence of something far more elusive and much closer to home.

On the horizon to the left, a rare atmospheric phenomenon called a sprite can be seen. These events are caused by irregularities in the ionosphere, high above storm clouds, at altitudes of about 80 kilometres. Typically seen as groups of red-orange flashes, they are triggered by positive cloud-to-ground lightning, which is rarer and more powerful than its negative counterpart, as the lightning discharge originates from the upper regions of the cloud, further from the ground. In a short burst, the sprite extends rapidly downwards, creating dangling red tendrils before disappearing.

The sprite pictured here was most likely over 500 kilometres away(compare with a satellite image showing the storm over Argentina), spanned a height of up to 80 kilometres and lasted only a fraction of a second.