On Wednesday morning many people around the world were treated to a full lunar eclipse that turned the moon a coppery shade of red.
The event also coincided with what is known as a supermoon—where a full moon is particularly close to the Earth due to its oval-shaped orbit.
As such, Wednesday's moon was dubbed the super blood moon of 2021, or sometimes the super flower blood moon to include the name of the full moon in May.
On their own, neither a lunar eclipse nor a supermoon are particularly rare. NASA data on lunar eclipses past and future shows there tends to be two or three lunar eclipses every year—though sometimes there's a couple years' gap between total lunar eclipses.
Supermoons, meanwhile, may happen two to four times in a row in a typical year. A supermoon is defined as a full moon that happens when the moon is within 90 percent of its perigee—or its closest approach to our planet.
So all of the above have to happen simultaneously in order for a super blood moon to occur.
The next super blood moon will appear on October 8, 2033. NASA's lunar eclipse data table for 2031 to 2040 shows there will be two total lunar eclipses in 2033—one on April 14 and one on October 8. The October 8 lunar eclipse will be visible from Asia, Australia, the Pacific, and the Americas.
Technically, there will be a few occasions in which a supermoon coincides with a lunar eclipse before 2033, on September 18 2024, January 12 2028, and June 15 2030. However, these will all be partial lunar eclipses and not full ones.
A full lunar eclipse means that the moon passes completely behind the Earth's shadow, darkening it in the sky.
A full lunar eclipse causes the moon to appear coppery red in the sky because although the sun's light is mostly blocked by the Earth, some light does still reach the moon by passing through the Earth's atmosphere first.
Due to the frequencies of sunlight and how these different frequencies are bent by the atmosphere, the reddish portion of the light is better able to reach the moon than the other colors.
