Super Blue Blood Moon 2018: Why the Term "Supermoon" is Misleading
An expert explains.
The Super Blue Blood Moon adorned the sky over [some parts] of the world early Wednesday morning. While it certainly lived up to the hype by dazzling stargazers, the reason why it’s being called a “supermoon” is actually pretty underwhelming.
Much like the “blue moon”, the supermoon is simply a naming convention for when the moon is a bit closer to Earth than it usually is, and it happens fairly often. In a video for Inverse, senior editor for the magazine Sky & Telescope J. Kelly Beatty explains how the moon got its actually not so super title.
“The total lunar eclipse on January 31 comes at a time when the full moon is especially close to Earth,” Beatty tells Inverse in a video. “Technically that’s called perigee but a lot of people know it as a ‘supermoon.’ That’s a term that was invented in 1979 by an astrologer, but really there’s not much super about it.”
The moon’s orbit around Earth is elliptical, meaning it’s not a perfect circle, so there are points during its journey around our home planet that it’s either closer or farther away.
The moon fully orbits the Earth in a little less than a month’s time. That means the moon could be in perigee two times in one month. That’s exactly what happened in January, as the Super Blood Moon on January 31 was the second supermoon of the year. According to Time and Date, it’ll be followed by 12 more this year.
While you might expect the moon to be gargantuan during these times, Beatty explains that it’s actually not all that epic.
“On the night of the eclipse the full moon will appear 6 percent bigger and closer than average and it will look about 11 percent brighter,” he says. “That’s really not a big difference, I certainly can’t tell. The only difference we’ll see is that astronomically this will raise tides in the oceans that are a little bit higher than normal.”
While this Super Blood Moon looked much wilder than your average, don’t expect the supermoons to follow to be sporting a cape or anything.