Cameras caught a space jellyfish

Found at: gopher.erb.pw:70/roman/phlog2022/436.txt

Cameras caught a space jellyfish fly over Georgia

In the wee morning hours of Thursday(May 5), a camera in
Waycross, Georgia witnessed a mysterious object streaking
through the sky. Bright, fast and trailed by a glowing oblong
aura, the object looked a bit like a space jellyfish, as Chris
Combs, a professor of aerodynamics and mechanical
engineering at the University of Texas at San Antonio put
it on twitter (https://bit.ly/3FrcNVC).
Of course, as Combs pointed out, this space jelly was no
UFO - it was a SpaceX Falcon 9 rocket launching from
Florida's Kennedy Space Center (https://bit.ly/3vXECBV),
roughly 250 miles (400 kilometers) south of the camera.
Dozens of rockets leave the launchpad at Kennedy every year,
but few of them could rightly be mistaken for a bioluminescent
invertebrate in the sky. So, what happened here?
According to Combs, it's a combination of physics and perfect
For starters, the long, blobby "body" of the jellyfish is simply
exhaust leaving the Falcon 9's rocket engine nozzle, Combs wrote.
The reason the exhaust takes on such a bulbous shape has to do
with the pressure difference inside and outside the nozzle. In
this case, the exhaust leaving the nozzle is "under-expanded"
- meaning the gas is at higher pressure than the ambient air around
it as the exhaust leaves the engine's nozzle.