On Monday, Aug. 19, the night sky was illuminated by a rare blue supermoon along with the appearance of vibrant “moonbows” throughout the United States. Lunar rainbows are a rare occurrence that mimics the appearance of solar rainbows but are lit by the moon instead of the sun. The only time to see a moonbow is during a full moon when the moonlight is at its strongest. But because moonlight is so much weaker than sunshine, their colours often look white to the naked eye.
The extraordinary brightness of the moon in the days preceding the supermoon made moonbows appear more vibrant. On the morning of August 18, astronomer Aaron Watson took a photo of a double moonbow over Paonia, Colorado. Another moonbow, this one fainter, was seen later that night above New York’s Keuka Lake.
Even though moonbows weren’t reported during the main supermoon, there’s still time to see one in the coming evenings. Moonbows can be seen when the moon is low in the sky, either immediately after sunset or before sunrise, when rain is falling and the moon is directly behind the observer. These elusive moonbows’ colours may appear more clearly in photographs, even though they look white in person.
