The moon left mouths agape around the world last night, larger and brighter than usual and glowing a melodramatic blood red—a spectacle that will not be seen again until 2033. This unusual occurrence was a rare mashup of a super-sized full moon and a total lunar eclipse, when the moon passes through Earth’s shadow. Even during a total eclipse, some of the sun’s rays filter through our atmosphere, leaving the moon with a spooky blood-red glow. Last night’s eclipsed moon was the last in a lunar eclipse tetrad, earning it the popular moniker "blood moon."
The greater size and brightness of last night’s supermoon can actually be seen at least once a year, when the full moon passes closest to the Earth in its elliptical journey around the planet. When the moon is in this position, called a perigee, it casts a silvery glow 30 percent brighter and 14 percent larger than when the orb is furthest away.
Though a supermoon or a lunar eclipse may not be rare on its own, the stars don’t often align for these events to occur in tandem. Since 1900, a supermoon lunar eclipse has only occurred five times, with the ruby orb last showing its enlarged face in 1982.