An amazing blue spiral observed in the sky in Alaska
Last weekend, a strange blue spiral appeared in the night sky in Alaska.
It is not the first time that a luminous whirlwind has caught the attention of sky watchers.
Last weekend, a strange luminous phenomenon appeared in the lens of aurora hunter Todd Salat, while he was near the town of Delta Junctio, Alaska. Against a background of rippling green light, a mysterious blue spiral suddenly appeared in the night sky. The astrophotographer was able to immortalize this celestial apparition.
"It was a magnificent work of art in the sky," described Todd Salat, who posted a high definition image on his website, to the Anchorage Daily News news site. Video captured by automated cameras at the University of Alaska also shows the whirlpool as it moves across the sky. As unusual as this sight may have been for Alaskans, it's not the first time a bright whirlwind has caught the eye of skywatchers.
Originally a SpaceX rocket
The explanation is actually quite simple. A few hours before the appearance of the spiral, at the other end of the continent, on the Californian base of Vandenberg, the SpaceX company launched a Falcon 9 rocket carrying satellites on board. Minutes after launch, the rocket's first stage dropped down and gently touched down on the Earth's surface, ready to be reused for future missions.
But the upper stage of the rocket continued its course towards orbit where it accomplished its mission, before descending towards the Earth, forming a spiral. By evacuating the remains of fuel in the upper atmosphere, the water vapor contained in the gases would have congealed into tiny crystals reflecting light, explains the Science Alert site.
The constellations of satellites that fill the night sky are becoming astronomers' nightmare. With the rise of the space industry and the falling cost of orbital technologies, these luminous spirals are likely to become more and more frequent. On January 19, a Japanese telescope, located at the Mauna Kea observatory on the island of Hawaii, had already observed a similar phenomenon.
Matthieu DELACHARLERY