A Rare And Spectacular Launch Phenomenon

There is a period of time when the sun has just set where conditions are perfect to illuminate a rocket high in Earth’s atmosphere as it ascends while it is nearly dark down on the ground where people are watching.

Conditions have to be perfect for this to happen: skies need to be relatively clear between you and the rocket, the Sun can’t be blocked by clouds between it and the rocket and it has to happen at just the right time of day. All that came together tonight here on the Space Coast, giving spectators a spectacular “jellyfish” that was the best in about two years. Rare indeed.

If you’ve ever been outside in the gloaming and seen a plane fly overheard still brightly lit by the Sun, you’ve seen the same thing. Some nights, the plane is leacing a contrail and it too is brightly lit. The sun is still above the the horizon from the plane’s perspective, but down below it has already set.

If that happens during a rocket launch, you get to see the rocket brightly lit as it climbs, and you also get to see a gaseous plume from the rocket’s engines brightly illuminated. The higher a rocket is, the lower the pressure of the atmosphere, so the exhaust plume expands to enormous proportions that can appear larger than your extended hand (or even two!) as you look up. It looks a lot like an iridescent jellyfish you might see in the ocean, hence the name.