“When this glowing spiral came toward me while growing rapidly, I thought, What The Heck?!?!,” Salat, a seasoned aurora hunter, wrote on his website. He frantically photographed the eerie spiral until it disappeared about seven minutes later. Other sky watchers also snapped images without the northern-lights backdrop. An all-sky camera from the University of Alaska captured a time-lapse of the event.
The culprit? The launch of a Falcon 9 vehicle by SpaceX three hours earlier from California. Researchers say such patterns have become increasingly common in recent years with more commercial satellite launches.
“It’s interesting to look at it, definitely not a UFO … It’s just SpaceX,” said Chris Combs, an aerospace engineer and assistant professor at the University of Texas at San Antonio. “It’s not restricted to just SpaceX, but we’re starting to see these a lot more often just because they’re launching so much more frequently.”
Researchers say the event was probably caused by excess fuel released during the launch. Water vapor or other gases in the engine exhaust may have frozen at the high altitude, forming ice crystals. The ice crystals reflect sunlight from space, which we can see from the ground.
The spiral shape formed because the rocket was spinning — like “water from a spinning sprinkler head,” said Carlos Martinis, a space physicist at Boston University.
The fuel was probably released from Falcon 9′s second stage as it was taking steps to de-orbit so it could safely lower in the atmosphere, said space physicist Don Hampton. The first stage, or lowest section of the system, is responsible for lifting the rocket off the ground and returns to Earth. The second-stage section of a rocket launch delivers the onboard payload to orbit, which were 51 satellites in this case. The second stage also burns up in the atmosphere, using a de-orbit burn to reposition itself so it can safely be discarded, such as over an ocean.
“That will require a motor burn to slow it down, and then many will also dump their remaining fuel,” Hampton, an associate professor at the Geophysical Institute at the University of Alaska at Fairbanks, said in an email. “What we saw was either the rocket exhaust or fuel dump — I can’t be sure without SpaceX confirmation.”
It doesn’t take much material to create such a bright-looking cloud, either, he added. He said the amount of material reflecting the sunlight was probably measured in just a few pounds, not hundreds.
“You can also see that it is spreading out very quickly, so concentration goes to nil after a few orbits,” Hampton said. “In the sunlight at those altitudes, any complicated molecules will be broken down into constituent atoms and simple molecules by the ultraviolet wavelengths in the sunlight.”
Most large rocket launches will produce a similar cloud, but observing it is more rare due to geography and timing. The exhaust or fuel needs to be in sunlight, and the ground needs to be dark. Hampton, who slept through the event but saw the time-lapse captured by his department’s all-sky camera, said clear skies in Fairbanks also allowed for an excellent view Saturday morning.
“I think the real uniqueness in this one is that you have the northern lights behind it, which is pretty cool,” Combs said.
Previous rocket launches have been linked to unusual patterns, including spirals. A Japanese telescope spotted a similar spiral in January over Hawaii after the SpaceX launch of the Falcon 9 rocket. Sky watchers in New Zealand saw a spiral after another Falcon 9 launch in June 2022.
At the moment, there’s no name for the rocket-induced spiral, although Combs said, “We should maybe have one at this point.”
“This is something that I think used to be more uncommon, but as the commercial launch industry and SpaceX are launching so much more, we’re starting to see it a lot more,” Combs said.