LUNAR RAINBOW CONTRAIL: Pilot and night-sky photographer Brian Whittaker has a knack for catching unusual sights from the cockpit as he flies back and forth from the USA to Europe. On July 3rd, he added “lunar rainbow contrail” to the list. “Although it was a beautiful evening seeing noctilucent clouds all night long from 38,000 feet, the coolest thing I saw was this iridescent contrail streaming from the wingtip of an Air France A380,” says Whittaker.
“We were flying east of Newfoundland, Canada, when the rising Moon lit up the contrail, creating a rainbow-colored streamer with stars sparkling above,” he says. “What a wonderful job.”
Although the contrail was rainbow-colored, it was not technically a rainbow, which requires raindrops. The contrail was filled with ice. Vortices of air that swirl behind flying wingtips create a low-pressure zone where water from humid air can condense. Sub-freezing temperatures produce crystals of ice which, in this case, split the light of the rising moon into iridescent colors.