(ORDO NEWS) — A camera in Waycross, Georgia, witnessed a mysterious object streak across the sky.
Bright, fast, with a glowing elongated halo, the object looked like a space jellyfish, Chris Combs, a professor of aerodynamics and mechanical engineering at the University of Texas at San Antonio, tweeted.
Of course, as Combs noted, this space jellyfish was not a UFO – it was a SpaceX Falcon 9 rocket launched from the Kennedy Space Center in Florida, about 250 miles (400 km) south of the camera.
Dozens of rockets leave Kennedy’s launch pad every year, but few of them can rightfully be mistaken for a bioluminescent invertebrate in the sky. So what happened here?
According to Combs, it’s a combination of physics and perfect timing.
For starters, the long, spherical “body” of the jellyfish is just exhaust coming out of a Falcon 9 rocket engine nozzle, Combs writes.
The reason the exhaust gases take on this bulbous shape is due to the difference in pressure inside and outside the nozzle.
In this case, the exhaust exiting the nozzle is “underexpanded” – meaning that the gas is at a higher pressure than the surrounding air when the exhaust exits the engine nozzle.
To match atmospheric background pressure, the rocket’s exhaust reduces its own pressure by expanding as it exits the nozzle, Combs says.
“In the underexpanded exhaust at the exit of the nozzle, fans are working to reduce pressure and bring it into line with background pressure: jellyfish at high altitude,” Combs tweeted.
This explains the clot. But what about glow?
According to Combs, it’s much simpler – it all comes down to time.
Since the rocket launch took place in the wee hours of Thursday morning (around 5:45 am local time (09:45 am GMT)), the light from the sun fell over the horizon, illuminating the exhaust plume, causing it to glow brightly against the dark sky .
Physics plus perfect timing – space jellyfish. A simple equation for a high-altitude spectacle.
Of course, if you want to see a real space jellyfish, you need to look a little further into space – more precisely, about 300 million light years further.
This is how far away the cluster of galaxies Abell 2877 is located; when astronomers recently looked at this object with a radio telescope, they saw the ghostly shape of a jellyfish floating through deep space.
This large jellyfish in the sky is also the result of a large gas explosion – in this case, a massive eruption from a group of ancient black holes, Live Science previously reported.
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