In a stormy Hawaii sky in July 2017, rays of red and blue light seemed to meet above a bed of white light.
The cameras on the Gemini North telescope at the Gemini Observatory in Mauna Kea took an impressive photo of the multicolored light show. The National Optical-Infrared Astronomy Research Laboratory (NOIRLab) released the photo on Wednesday as its “image of the week”.
The lightning bolt in the image “looks so supernatural that it looks like it must be a special effect,” said NOIRLab. He also published a zoomed version.
These colorful lightning phenomena are aptly known as red sprites and blue jets. They are extremely difficult to capture on camera: flashes last only tenths of a second and can be difficult to see from the ground, as they are often obscured by storm clouds.
According to Peter Michaud, NOIRLab’s education and engagement manager, astronomers from nearby Hilo use the telescope’s cameras to remotely track the bad weather that is forming near the observatory. The camera system takes a picture of the sky every 30 seconds.
“We saw some other examples of similar phenomena, but this was the best example of a lightning sprite in the upper atmosphere,” he told Insider.
Red, white and blue
Regular white lightning strikes are different from sprites and jets in several important ways. While regular lightning strikes between electrically charged air, clouds and ground during storms, sprites and jets start at different locations in the sky and move into space. Their distinctive hues also set them apart.
Red sprites are ultra-fast bursts of electricity that pop through the upper regions of the atmosphere – between 37 and 50 miles in the sky – and move towards space. Some sprites are shaped like jellyfish, while others, like the one in the Gemini Observatory image, are vertical columns of red light with tendrils snaking downwards. These are called carrot sprites.
Stephen Hummel, a dark sky expert at the McDonald Observatory, captured a spectacular image of jellyfish elves from a ridge on Mount Locke, Texas, last July (below).
“Sprites generally appear to the eyes as very brief, cloudy and gray structures. You need to be looking for them to locate them, and I’m often not sure if I really saw one until I checked the camera footage to confirm,” Hummel Insider at the moment.
Davis Sentman, who worked as a physics professor at the University of Alaska Fairbanks, proposed the name “sprite” for the red lightning phenomenon. He said the term was “well suited to describe his appearance,” since the word evokes fleeting, lightning-like nature. Sentman died in 2011.
Blue jets, in turn, are born closer to Earth than red sprites. These cone-shaped electrical discharges are also brighter than sprites and explode from the top of clouds. The peaks of the storm cloud can be anywhere from 1 to 14 miles above the Earth’s surface; the blue jets continue to move towards the sky until they reach a height of approximately 30 miles, when they disappear. These jets move at speeds of more than 22,300 mph.
Sprites and jets can be seen from space
When a regular lightning strike hits the ground, it tends to release positive electrical energy that needs to be balanced by an equal and opposite charge energy anywhere in the sky. Thus, sprites and jets are the electrical discharges that balance the equation – that is why these colorful lightning phenomena occur.
“The more powerful the storm and the more lightning it produces, the more likely it is to produce a sprite,” said Hummel.
Astronauts can sometimes locate sprites and jets from the International Space Station, 250 miles above Earth.
European Space Agency astronaut Andreas Morgensen captured elusive blue jets on video for the first time in color in 2015. He spotted the jets while filming a storm in the Bay of Bengal, India. Later, scientists used the footage as part of a 2017 study.
Morgensen’s observations “are the most spectacular of their kind,” wrote the study’s authors.
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