While I was observing the skies above the La Silla observatory during the majestic night 19/20 January 2015, I didn’t know that was possibly the best night for capturing airglow in my life. It started after the sunset, when I was focused on observing and capturing of the comet Lovejoy passing Pleiades. A waves of redish airglow were moving from the east, where also were located huge MCS storms visible before the nightfall. The night were going on, while I spent a time on the platform of 3,6m telescope of La Silla and via the camera was witnessed by much more red airglow not only in the direction of the storms, but also above my head. The slowly moving red stripes covered all the sky, while the north-east horizon had a greenish-yellow hue. The biggest surprise came a few hours before the sunrise, when the sky was covered by structures visible even by naked eyes. The surprise was even bigger, because I noticed first Red Sprites flashing above the far mountains, just form the direction of the evening gravity waves. It took me a time wondering how many TLE phenomena I capture, so I went back to the hotel just before the daybreak. Watching the rising Scorpius constellation with strong shine of the zodiacal light, I took one more panorama of the sky and it made me shocked again. On the last image is totally new azure-green structure looking like a comb in the sky. This night was obviously something like a ZOO of the airglow colors.
Colors of airglow above the La Silla Observatory – Poster
As written on the Atmosphere optics webpage, the Sun’s extreme ultraviolet light excites oxygen and nitrogen atoms and molecules in the thermosphere. The energetic products collide and interact with other atmospheric components, including hydroxyl radicals (OH), to eventually produce light emission by chemiluminescence and and decay of excited atoms and molecules. As seen on the image(s), the airglow during the night was really various. The most noticable was orange and reddish hue caused by atomic oxygen in 150-300 km above the ground. This one was seen just after the sunset in gravity waves from the south to the east. Darker red luminiscating is most likely produced by the OH radicals in about 88 km and the most noticable is the airglow in the sky from the 3.6m platform (right top panoramatic view). On the image is also yellow-green color above the north to the west horizon. It was emited by the oxygen atoms far away, about 90-100 km especially above the Pacific ocean that direction. The most interesting are, however, the bottom images, where the variety of the airglow gets to the maximum. You can see a waves with green and deep red colors following the green. Those waves are probably 80-100 km high and following by azure-green isolated cloud of strong excitation of the atomic oxygen. Of course, you can also enjoy the view to the Milky way with hydrogen nebulae in Vela constellation and Orion, the hunter, with the zodiacal light, zodiacal bridge and the Gegenschein close to the planet Jupiter.
The detailed fish-eye images are the results of my major purpose of the January visitation of the ESO observatories – ultra HD fulldome panoramas. Those panoramas are usually more than 14×14 thousands pixels big and created for fullfome digital planetariums. Thanks to that the resolution of the original images the details of the structures of the airglow is incredible. For all images was used Canon 6D, Samyang 24 mm, f2.0, ISO 8000-10000 (individual for every panorama), 45-52×15 s (stitched to the fulldome panoramas).
The poster in full resolution (3661×4488 px, PNG; 12,8 MB) you can download here: The types of airglow.