January 31 is a day to mark on your calendar if you fancy yourself a space enthusiast. A Super Blue Blood Moon — an event veteran space reporter J. Kelly Beatty calls an “astronomical trifecta” — will be visible in a few places across the globe.
Beatty, the senior editor for the magazine Sky & Telescope, explains that this event is the crossover of three distinct lunar occurrences.
“In addition to the total lunar eclipse, that event occurs when the moon is about its closest to Earth,” Kelly tells Inverse. “Technically that’s called perigee, but it’s widely known as a ‘supermoon.’ And in addition, it’s the second full moon of the month.”
Total lunar eclipses are colloquially known as “blood moons.” That’s because the moon is completely in the Earth’s shadow, so light from the sun is scattered through our atmosphere before it hits the moon, causing us to see a crimson moon. This is a phenomenon known as “Rayleigh’s scattering.”
As Kelly explains in the video above, this will occur as the moon is in perigee, something that happens fairly often. What really makes the January 31 eclipse special is that it’s the second full moon of the month, an occurrence known as the “blue moon.”
“Perigee lunar eclipses are actually pretty common, the last total lunar eclipse in December of 2015 came at perigee and so too will the one around this time next year, in January 2019,” says Kelly. “Those blue moon eclipses are less common. The last time a total lunar eclipse happened on the second full moon of the month was December 30, 1982.”
The overlapping of these three lunar events — the supermoon, the blood moon, and the blue moon — is what gives this Wednesday’s eclipse its wordy title.
The last time these three things coincided was in 1866, so if you’re lucky enough to be able to catch a glimpse of the the moon on January 31, make sure you take some pictures.