On October 8, French astronaut Thomas Pesquet captured something strikingly rare from on board the International Space Station (ISS).
The photo – which is a single frame taken from a longer timelapse – might look like it shows a cobalt bomb exploding over Europe, but this scary-looking blue light didn't do any damage. In fact, most people would never have noticed it happening.
Instead, the frame shows something far less ominous called a 'transient luminous event' – a lightning-like phenomenon striking upwards in the upper atmosphere.
Also known as upper-atmospheric lightning, transient luminous events are a bunch of related phenomena which occur during thunderstorms, but significantly above where normal lightning would appear. While related to lightning, they work a little bit differently.
There are 'blue jets', which happen lower down in the stratosphere, triggered by lightning. If the lightning propagates through the negatively charged (top) region of the thunderstorm clouds before it gets through the positive region below, the lightning ends up striking upwards, igniting a blue glow from molecular nitrogen.
Then there are red SPRITES (Stratospheric/mesospheric Perturbations Resulting from Intense Thunderstorm Electrification) – electrical discharges that often glow red, occurring high above a thunderstorm cell, triggered by disturbances from the lightning below – and slightly dimmer red ELVES (Emission of Light and Very Low Frequency perturbations due to Electromagnetic Pulse Sources) in the ionosphere.
Sticking with the theme, there are also TROLLs (Transient Red Optical Luminous Lineaments) which occur after strong SPRITES, as well as Pixies and GHOSTS. We're sure the scientists had lots of fun naming all of these phenomena.
"What is fascinating about this lightning is that just a few decades ago they had been observed anecdotally by pilots, and scientists were not convinced they actually existed," Pesquet explains in a photo caption.
"Fast forward a few years and we can confirm elves, and sprites are very real and could be influencing our climate too!"
Although Pesquet doesn't explain specifically which type of luminous event we're seeing, this particular image could be showing a 'blue starter', which is a blue jet that doesn't quite make it to the jet part, and instead creates a shorter and brighter glow.
These events are particularly hard to photograph from the ground as they are both very high in the sky and also regularly obscured by storm clouds. Plus, the phenomena usually only last for milliseconds or a couple of seconds each time.
With all those things in mind, it makes the ISS a particularly great place to look for these transient events, particularly if you have a timelapse turned on. So far we've seen a number of these events captured by astronauts on the ISS, and a small number taken from the ground.
Interestingly, Earth isn't even the only place where the light shows take place, with researchers discovering just last year that 'blue sprites' were occurring on Jupiter too.
"The Space Station is extremely well suited for this observatory as it flies over the equator where there are more thunderstorms," says Pesquet.
"This is a very rare occurrence and we have a facility outside Europe's Columbus laboratory dedicated to observing these flashes of light."
We hope that this research will give us plenty more photos of this incredible phenomena in the future!