Anyone who has watched a SpaceX launch near sunrise or sunset has probably seen it: a vast, glowing plume spreading across the sky like a jellyfish.
Jon Bell, associate professor of astronomy and director of the Hallstrom Planetarium at Indian River State College, says the phenomenon is striking but not mysterious.
“They are very, very beautiful, and they are very unusual, very alien-like, but it’s actually a little bit simpler than you might imagine,” Bell said.
Bell compared the rocket plumes to the contrails jets leave on humid days.
“As the exhaust comes out of the jet, the water in there is going to freeze and make ice crystals, and that’s what you see as the plume,” he said. “Same thing with spaceships.”
The plumes are most visible around dusk or dawn, Bell said. In full daylight, the sky is too bright for them to stand out.
“You don’t see them in the daytime so much because the blue sky is so bright, but they are there nevertheless,” he said.
Bell said the Falcon 9’s kerosene-based fuel helps give SpaceX launches their distinctive look. He said the rocket is also efficient and economical, which is why he expects the company to keep using it. That means more jellyfish plumes for Treasure Coast residents who catch a launch at the right hour.
“It’s wonderful to live in this part of Florida where you can watch these things for yourselves,” he said.
The next scheduled launch is Wednesday, October 28 at 8 pm.
His advice for catching a jellyfish: “Any time there’s a launch in the evening hours or the predawn hours, look for that jellyfish to appear.”