On the morning of Dec 9th, many in Norway were treated to a beautiful sight. An enormous, pearlescent, spiral lit up the twilight sky. Of course, some suspect it to be of extraterrestrial alien origin. There is a better explanation though: it was a twilight-affected rocket launch. A no-fly alert was issued for the area over the White Sea on Dec. 9th. In 2005, we watched a scheduled evening twilight Minotaur launch from Vandenberg AFB about 400 miles to the west. It was a stunning and very unusual sight.
That launch did not, however, sport a spiral. If you've ever launched a model rocket and didn't have the fins attached correctly, you may have noticed a crazy spiral smoke trail as your creation soared (wobbled) into the sky--or into the ground nearby. See this photo of an ill-advised horizontal launch from many years ago (my buddy Chris is hiding behind the dirt berm in the background).
It looks to me like something similar happened over Norway, which would mean the rocket may have failed, causing it to spin and eject fuel in a spiral pattern as it soared away. In most of the images, you can see two spirals: a large, diffuse spiral, and a brighter, tighter spiral at its core. This is similar to what we saw with the Minotaur launch, which was a diffuse and rapidly expanding outer shell, with a tighter, more stable core of material in the center. It seem to me that this may be due to different compositions in the exhaust: lighter, more volatile material that spreads quickly and easily in the tenuous upper atmosphere, and denser material that doesn't spread so readily.
Rocket launches that are backlit by the sun while your observing location is still dark are fantastic sights. In fact, another evening twilight launch is tentatively scheduled for a Minotaur IV launch in the near future: Vandenberg AFB Launch Schedule. I'll be keeping my eyes peeled!
[[Update: Russian Defense Ministry has confirmed this was a failed test ICBM launch: BBC News.]]
