Mysterious glowing 'SpaceX spirals' in the night sky seem to be linked to rocket launches

• Photos and video show a mysterious, glowing spiral swirling across Alaska's night sky on Saturday.
• It's likely a cloud of excess fuel from a SpaceX rocket launched earlier that day. 
• "SpaceX spirals" are rare, but they may be getting more common.

Mysterious, glowing blue spirals have appeared in the night sky several times in recent months, and they may be linked to SpaceX rocket launches.

The most recent of these ghostly apparitions spun across the skies over Anchorage, Alaska on Saturday, during a display of the Northern Lights.

"I was totally bewildered," Todd Salat, a local aurora hunter who was watching the spectacle, told Insider in an email.

He shared the below timelapse of the mysterious spiral swirling across the sky before it dissipated.

It almost looks like a giant galaxy popped into existence nearby. But the reality is not so fantastical.

These spirals are appearing shortly after SpaceX rocket launches, and are probably residual fuel the rockets released during flight, space physicist Don Hampton told the Associated Press. In fact, some space observers have begun calling them "SpaceX spirals."

That's because the fuel turns into ice if it's released at a high altitude.

"And if it happens to be in the sunlight, when you're in the darkness on the ground, you can see it as a sort of big cloud, and sometimes it's swirly," Hampton told the AP.

SpaceX spirals, jellyfish, and smoke rings may happen more often

This is the third time in the past year that a Falcon 9 rocket has appeared to produce a SpaceX spiral.

The apparition danced among the Northern Lights for a few minutes before dissipating, according to observers. That was about three hours after SpaceX launched a Falcon 9 from California's Vandenberg Space Force Base toward the North Pole.

A similar whirlpool spiral appeared over Hawaii in January, and the National Astronomical Observatory of Japan said at the time that it was probably linked to SpaceX as well.

After a Florida launch in June 2022, a similar spiral was seen over Queenstown, New Zealand, The Washington Post reported.

"They have occasionally been seen in other contexts, particularly Russian missile defense tests," Jonathan McDowell, a Harvard astrophysicist, told Insider.

The reason Falcon 9 keeps producing these spirals is that it fires its engines while deliberately "coning" — rolling in a cone-like shape — to waste fuel, according to McDowell. That happens when the rocket has more fuel than it will burn to push itself into a freefall back to Earth.

"Other rockets sometimes just vent the leftover propellant after the burn is done, but perhaps there isn't enough time to do this reliably on [Falcon 9]," McDowell said.

Falcon 9 rockets have made other colorful and ethereal formations in the sky, too. The launch that could have produced the New Zealand spiral may have also created a "smoke ring" formation in the skies above the central US, according to SpaceWeather.com.