Early Friday morning, a red moon will darken over Chicago skies. It will be the first of two total lunar eclipses this year — and the only one visible from North America.
This lunar phenomenon is different from the rare total solar eclipse that swept over U.S. skies almost a year ago. It happens when the moon darkens as it passes through the Earth’s shadow, which is cast into space when sunlight falls on the other side of the planet. If the moon is full, it dims completely, causing a total lunar eclipse.
“On average, lunar eclipses happen about twice a year, but not all of them are total — and not all of them can be seen from (the same place),” said Michelle Nichols, director of public observing at the Adler Planetarium.
The last time Chicagoans saw a total lunar eclipse was Nov. 7, 2022. There have been more eclipses of the moon since then, “but those either weren’t visible from our area or they weren’t total,” Nichols said. So, while not as rare as a total solar eclipse, Friday’s is still an unusual occurrence.
At 10:57 p.m. Thursday, the full moon will begin to enter the Earth’s lighter, outer shadow, or the penumbra. Looking southwest, Chicagoans will see a partial eclipse as the moon more noticeably darkens from 12:09 a.m. to 3:47 a.m. Friday. At that time, the celestial body will be passing the Earth’s darker inner shadow, or umbra.
Totality, or the darkest period of the eclipse, will last roughly one hour from 1:26 a.m. to 2:31 a.m., the maximum occurring at 1:58 a.m. The moon will fully exit the Earth’s shadow at 5 a.m. Friday, ending the eclipse.
When does a lunar eclipse occur?
According to the Adler Planetarium, a lunar eclipse can only happen during the moon’s full phase when it is opposite the sun with the Earth right in the middle. This allows the entire side of the moon that is facing the planet to be illuminated at night as it reflects sunlight.
Even though there is a full moon every time the moon completes its orbit — about once every month — lunar eclipses only happen once or twice a year. This is because its orbit is tilted relative to Earth, meaning the moon usually passes slightly above or below the shadow.
The March full moon was dubbed the “Worm Moon” by Native American tribes, according to the Old Farmer’s Almanac, because it occurs when earthworms come out of the ground as it thaws in the spring or when beetle larvae emerge as the bark of trees and other winter hideouts thaw.
Why does the moon turn red?
The moon dims during a total lunar eclipse, but it doesn’t generally disappear during totality. It often takes on a rusty, reddish color, which gives it its common name of “Blood Moon,” according to the Adler.
This color comes from the sunlight that passes through the atmosphere, which scatters blue rays away and allows red wavelengths to pass through it and into the shadow of the Earth.
“It’s passing through air on the entire edge of the Earth at that point,” Nichols said. “So you’re basically seeing the collective sunrises and sunsets happening on Earth at that exact moment in time.”
But not all total lunar eclipses make the moon turn red.
“There’s a wide range of colors,” Nichols said, such as deep brick red, bright orange or dark gray. “The color can change from one (eclipse) to the next because of how clear or cloudy the air is when the sun’s light is passing through.”
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For instance, the deep red color of the total lunar eclipse seen from Chicago on November 2022 has been attributed to the massive eruption of the Hunga Tonga-Hunga Ha’apai volcano in the Pacific nation of Tonga in January of that year which released sulfate aerosols into the atmosphere that reflected sunlight, according to the U.S. National Science Foundation’s National Optical-Infrared Astronomy Research Laboratory.
What makes a ‘total’ lunar eclipse?
The type of lunar eclipse is determined by how much of the moon passes through Earth’s inner and outer shadow, according to the Adler.
When it passes through the lighter, outer shadow area, or the penumbra, it’s a penumbral lunar eclipse. The moon may appear tan in color, but the change is often hard to notice.
When only a part of the moon passes through the darker, inner shadow area, or the umbra, it’s a partial lunar eclipse. The moon looks like a bite has been taken out of it that grows bigger as it continues its journey through the Earth’s shadow.
When the moon passes completely into the umbra like it will Friday, it’s a total lunar eclipse.
Tips to watch
Only people on the side of the Earth facing the moon will see a lunar eclipse. On Friday, it will be visible for all of the United States, Canada, Mexico, Central and South America — if skies are clear.
Experts recommend checking local weather and cloud coverage forecasts. According to a National Weather Service digital forecast map Wednesday, skies over Chicago will be 35% to 55% cloudy between 1 a.m. and 3 a.m. Friday during the darkest period of the eclipse.
Meteorologists from AccuWeather cautioned the public that a “cross-country storm” that slammed the West Coast with rain and snow Wednesday could trigger thunderstorms, hail, damaging winds and possibly tornadoes in parts of the central U.S. Friday through Saturday, affecting eclipse viewing for millions.
Those observing outdoors should dress appropriately for a long wait and find a spot unobstructed by tall buildings and trees. There is no need for special equipment such as binoculars or telescopes.
Those at home are invited to join Nichols from the Adler and Hunter Miller, an astronomer educator at the planetarium, in the free YouTube livestream “Sky Observers Hangout” shortly after midnight. The experts will be viewing the eclipse from Carbondale in southern Illinois, which had the unique opportunity of being in the path of totality for the total solar eclipses of 2017 and 2024. Viewers will be able to interact with them over chat, ask questions and learn to stargaze from home with everyday objects.
More eclipses to come
This week’s lunar eclipse will be the only one visible from North America in 2025; the second one, also total, will happen Sept. 7 over Australia, Asia, Africa and Europe.
Lunar eclipses often happen in tandem with a partial or total solar eclipse — which usually occurs two weeks before or after — since the moon’s orbit is lined up just right with the Earth and sun. The one caveat is that both kinds of eclipses might not be visible from the same parts of Earth, and they may not be total.
On March 29, a partial solar eclipse will follow Friday’s lunar happening, though it won’t be visible from Chicago — only in the Northeast where there is an unobstructed view of the horizon. On Sept. 21, a second partial solar eclipse will be visible only from the South Pacific, New Zealand and parts of Antarctica, according to the Old Farmer’s Almanac.
The next total lunar eclipse visible from Chicago will be March 3, 2026.
