Rare 'moonbows' light up night sky across US as blue supermoon rises — and you could still spot another one

Extremely rare, vibrant "moonbows" were spotted in the night sky above the U.S. shortly before the rise of the blue supermoon on Monday (Aug. 19).

The moon will remain bright for the next few nights, meaning you still have a chance to see this ethereal phenomenon for yourself, if you're lucky. And we can tell you how.

Moonbows, also known as lunar rainbows, are created in the same way as their solar counterparts, with one obvious difference: they appear when moonlight, rather than sunlight, reflects and refracts off falling raindrops. But they are much rarer because they can only be seen around a full moon, when our planet's natural satellite is at its brightest in the night sky.

Even then, the moonlight is so faint compared to the sun that the luminous arches normally appear white — that's because the color-detecting receptors in our eyes don't work well enough in dim light to distinguish between the spectrum of colors produced — namely, "ROYGBIV," according to the U.K. Met Office.

However, the moon has been unusually bright over the last few days in the lead-up to the "once-in-a-decade" blue supermoon, allowing more impressive examples of this phenomenon to emerge.

Related: 10 bizarre phenomena that lit up the sky (and their scientific explanations)

Astrophotographer Aaron Watson spotted a stunning double moonbow above Paonia, Colorado, at around 2 a.m. ET on Sunday (Aug. 18), Spaceweather.com reported.