Moving spiral appears over the Alaskan sky

The lens of photographer Todd Salat, an expert in auroras, recorded an interesting phenomenon the last Saturday.

Suddenly, high above the Alaskan sky, a weather phenomenon occurred, unlike anything he had ever seen before.

As he later described, against a stunning backdrop of rippling green light, a sort of blue spiral with brilliant light emerged on the northern horizon, one that grew larger as it moved rapidly across the sky.

The following clip shows those moments more clearly:

The explanation, as they point out in ScienceAlert, is simpler than one might expect.

Apparently a few hours before the spiral appeared, half a continent away at California's Vandenberg Space Force Base, SpaceX launched a Falcon 9 rocket containing dozens of satellites as part of its Transporter-7 mission.

After launch, the first-stage rocket returned to the surface and landed softly, available for reuse on future missions.

However, the Falcon 9 upper stage continued in orbit where it completed its mission before descending back to Earth in a rotating spiral. In fact, by "releasing" its leftover fuel into the upper atmosphere, the water vapor in the gases would have frozen into tiny, light-reflecting crystals.

This is not the first time that a similar phenomenon has occurred after rocket launches, so this option should be considered much more likely, or at least more likely than a possible invasive cosmic jellyfish.