By now you’ve likely heard about a rare cosmic event taking place before the crack of dawn Wednesday: the “super blue blood moon.”
The event, which last occurred in the U.S. more than 150 years ago, will result in the moon taking on a reddish tint as it passes through the Earth’s shadow, though it will be visible only to viewers in the westernmost parts of North America and Hawaii.
Chicago sky-gazers will hardly see any of the blood moon, and possibly none of it at all given the cloudy forecast.
“This particular lunar eclipse is not well-placed for Chicago,” said Michelle Nichols, director of public observing at Chicago’s Adler Planetarium. “If people want to sleep in for this one, I totally understand.”
Those able to see it will witness the convergence of three lunar events: a blood moon, supermoon and blue moon.
A blood moon takes place during a lunar eclipse, when Earth’s shadow casts a red or copper hue on the moon’s surface.
A moon is considered “super” when it is closest to Earth in its orbit, a point known as the perigee, causing the moon to appear about 14-percent brighter than normal.
A blue moon, meanwhile, is the second full moon in a single month – and has nothing to do with the color blue or the appearance of the moon at all.
“The moon can appear bluish at times, but that doesn’t necessarily coincide with when it’s the second full moon in the calendar month,” said Nichols, adding that the blue moon is simply a convention of the 12-month Roman calendar. “It’s a total human construct.”
The hype surrounding this week’s event is somewhat overblown anyway, Nichols said. That’s because the perigee of the moon’s current orbit – the point at which it is closest to Earth – will actually occur almost a full day earlier, just before 4 a.m. Tuesday.
And this moon won’t be as “super” as it was during previous orbits earlier in January or in December, when it was closer to the Earth (and brighter in appearance).
“That’s the supermoon that we all needed to pay attention to,” Nichols said, referring to the supermoon on Jan. 1. “We’re stretching this supermoon story thing a little bit. But if this is what gets people to look up at the sky, fantastic.”
Weather permitting, the event will still offer a unique experience for viewers in places like California, Oregon, Washington, Alaska and especially Hawaii.
“When the eclipse starts, they’ll see what looks like this shadowy bite taken out of part of the moon, and then that shadow will appear to sweep more across the face of the moon,” Nichols said. “In reality, it’s the moon moving into the Earth’s shadow. And then when it’s actually in the shadow, that’s when you see that reddish color.”
The moon could also appear gray, depending on weather conditions.
“If the atmosphere is cloudy in those areas, if there’s been some volcanic eruptions, if it’s dusty, these conditions can change the color,” Nichols said. The color will be the result of “the collective light of the sunrises and sunsets around the entire edge of Earth,” she said.
In Chicago, Nichols said the moon will be just 2 degrees above the horizon when it is fully within the Earth’s shadow starting at 6:45 a.m. Wednesday, resulting in an unremarkable viewing experience.
For those who want a glimpse of the blood moon, NASA is livestreaming the event.
The next super lunar eclipse visible across the U.S. will take place Jan. 20, 2019. It won’t be a blue moon, but it should be visible in Chicago.
“Weather permitting, we’ll see the entire eclipse,” Nichols said.
Aug. 21: Adler Planetarium astrophysicist Lucianne Walkowicz joins us from the eclipse epicenter in Carbondale.
Aug. 21: About a dozen different species were under close watch during the event as scientists looked for any changes in behavior.
Aug. 21: Chicagoans from all neighborhoods and walks of life came out of the shadows to fix their appropriately covered eyes on the skies.