When Is The Blue Moon? You Better Make Sure To Sneak A Peek Since It Won't Be Back For Years

Sorry to be the bearer of bad news, but a "blue moon" isn't actually blue (I know, bummer). Still, if you get a chance to check it out, you should step out and see when the next blue moon comes up Friday, July 31. Even if it's not the shimmering cobalt sphere you imagined it would be, it's still going to be pretty spectacular. And if you miss out on this one, don't even bother booking your calendar ahead — the next one won't crop up until 2018.

In reality, though the best time to view this Friday's blue moon will actually be Thursday night, since the moon will reach "peak fullness" around 5:42 a.m. CT on Friday morning, reported AL.com. So unless you're planning on pulling an all-nighter, you'll need to sneak a peek a little earlier than scheduled.

"According to modern folklore, whenever there are two full Moons in a calendar month, the second one is 'blue,'" wrote NASA in a statement on Monday. "Most Blue Moons look pale gray and white, just like the Moon you've seen on any other night [since] squeezing a second full Moon into a calendar month doesn't change its color."

LOUISA GOULIAMAKI/AFP/Getty Images

I love it when you're sassy, NASA. Of course, the space agency is right: In order to truly cause the moon to turn blue relative to our perspective here on Earth, you'd need a massive explosion like a volcanic eruption. When the Indonesian volcano Krakatoa erupted in 1883, for example, the ensuing plumes of ash scattered enough red-cloaking micro-particles (which, conversely, allowed blue light to pass through) into the atmosphere that the moon looked like a truly dapper, turquoise version of itself. Not that it's worth the cataclysmic fallout of a devastating eruption or anything. But it was pretty nonetheless, and more remarkably, the phenomenon reportedly lasted for years following the eruption.

Don't be surprised either if the moon betrays your sense of color and shows up red. According to NASA astronomers, Luna (that's the moon's official, Latin name) will sometimes take on a fiery hue, thanks to all the particulates in the sky that scatter blue light. They explained:

Often, when the Moon is hanging low, it looks red for the same reason that sunsets are red. The atmosphere is full of aerosols much smaller than the ones injected by volcanoes. These aerosols scatter blue light, while leaving the red behind. For this reason, red Blue Moons are far more common than blue Blue Moons.

The last blue moon to grace us with its presence showed up way back in 2012, and the upcoming blue moon will be the last until Jan. 31, 2018, according to The Old Farmer's Almanac. After that, the next occurrence won't take place until 2037. Plan accordingly.

Images: Getty Images (1)