Driftless Dark Skies: In the Shadow of the Earth

January 11th, 2019 by John Heasley

On the evening of January 20, moongazers in the Driftless Region can be awed by a total lunar eclipse. That’s when our moon passes through the shadow of the Earth and darkens in color to copper or rust or brown or grey. Unlike the total solar eclipse that wowed us in August 2017 when the shadow of the moon trekked across North America, you don’t need to travel to experience totality. It will be visible everywhere in the western hemisphere at the same time. It’s a slow and meditative event. And totality lasts for over an hour instead of the two minutes of totality for the solar eclipse.  I love the way both solar and lunar eclipses take us out of the ordinary as the familiar shapes of sun and moon become weird.

graphic by Leah Tiscione / Sky & Telescope

Enjoying a lunar eclipse is pretty easy. It’s January in the Driftless, so bundle up. Remember you don’t need to stay out the whole time. The pace is leisurely, so you can go inside to warm up. The moon rises in the northeast around 4:34 just as the sun sets in the southwest around 4:56. The moon is closest to Earth on January 21, so it may appear a little bigger and brighter in the sky. The Full Wolf Moon will be fairly high in the sky when it enters Earth’s penumbral shadow at 8:37. The effect is subtle. You won’t notice much at first, but by 9:10, you should start seeing some darkening of the moon beginning on its lower left limb. Take time to have a look at Mars in the southwest before it sets by 11:11. The umbral phase begins at 9:34 as Earth’s shadow starts taking bigger and bigger “bites” out of the moon. This is where things start to get weird as we see the moon with unfamiliar phases and colors. If you can only see part of the eclipse, head out around 10:30 as we move from partial to total eclipse. Even if you’ve seen a lunar eclipse before, don’t miss this one. Like memorable plays at American Players Theatre, each performance is unique.

Totality lasts from 10:41 until 11:43 with maximum eclipse at 11:12. This is when the moon is most colorful. It’s hard to predict what color we’ll see. Even though Earth is between sun and moon and totally covers the sun, our atmosphere refracts the sunlight and some of it still reaches the moon. How much depends on clouds and particles in our atmosphere. Our atmosphere scatters the blue light, but the reds and oranges pass through to eerily light up the moon. Be sure to watch as more and more stars emerge as the moonlight is dimmed and the sky darkens. Binoculars are a great way to watch Earth’s shadow making its way across the surface of the moon. You can also use them to check out the sparkling Beehive Cluster to the left of the moon about a dozen moon widths away and the twin stars Castor and Pollux in Gemini lined up above the moon.

After totality, everything happens in reverse for the hardy eclipse watchers as the moon orbits out of Earth’s shadow and goes through those weird phases. You’ll see the first brightening of the moon on the upper left limb and traveling across the face of the moon until the umbral phase ends at 12:50.  The moon continues to brighten until 1:48 when it finally leaves the penumbral shadow of the Earth. If you’re too caffeinated to sleep by this time, you can enjoy the winter sky becoming familiar once more, Jupiter and Venus rising together in the southeast around 4:15, the sun rising around 7:27, and the moon setting around 7:51.

2019 is the Year of Apollo, when we celebrate the 50th anniversary of humans first leaving the Earth to walk on another world. It’s fun to imagine ourselves viewing the eclipse from the Sea of Tranquility where Neil Armstrong and Buzz Aldrin landed the Eagle during the mission of Apollo 11. From there, Earth is always in the same spot in the sky directly overhead and much bigger and brighter than the moon appears from Earth. We would see it rotating once every day and going through the phases of Waxing Crescent, First Quarter, Waxing Gibbous, Full, Waning Gibbous, Last Quarter, Waning Gibbous, and New Earth every month. Lunar eclipses occur when the moon appears full from Earth and Earth appears new from the moon. Earth would be challenging to see because it’s so dark and close to the sun. From the moon, we would be seeing a total solar eclipse as Earth begins to take bites out of the sun until it totally blocks it.  During an hour of totality, we could be awed by the sun’s wispy corona streaming out and a ring of fire surrounding the totally dark Earth. We’re watching all the sunrise and sunsets on Earth all at once as its atmosphere refracts the light. Maybe we would even see some of the city lights of the Americas. We would notice the moonscape around us change color from grey to copper and rust and maybe even begins to resemble a Marscape.

Lunar eclipses are somewhat rare, though not as rare as solar eclipses. The last lunar eclipse we saw in the Driftless was last year on January 31, 2018. The next ones won’t be for another two years when we will be treated to a tetrad of four lunar eclipses in May and November of 2021 and 2022 much as we saw a tetrad of four lunar eclipses in March and September of 2014 and 2015. But don’t wait. This one starts at a fairly friendly time, the next day is a federal holiday, and you never know when clouds might get in our way. Carpe noctem/Seize the night!

John Heasley is an astronomy educator and stargazer who enjoys connecting people with the cosmos. He volunteers with NASA/JPL as a Solar System Ambassador. For more information about stargazing in southwest WI, like Driftless Stargazing LLC on Facebook and find out whenever there’s something awesome happening in the skies. Driftless Dark Skies appears monthly in the Voice of the River Valley.

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