The first total lunar eclipse of 2021 will take place early next week and will show the largest full moon of the year.
Ready for the end of the lunar eclipse drought? It’s been a while since we’ve seen the moon go through the earth’s dark inner shadow to be sure. In 2020 there were four lunar eclipses … all of them weak penumbra. In fact, you have to go back all the way to January 21, 2019 (do you remember 2019?) To remember the last total lunar eclipse. But that wait ends next Wednesday morning on May 26th with a very brief total lunar eclipse focused on the Pacific region.
The solar eclipse occurs in the early hours of the morning for western North and South America and at dusk for Far East Asia and Australia. Europe, Africa, and the Middle East are missing out on the event completely, and most of eastern North America only sees the very early partial phases of the sunrise and moonset solar eclipses.
Eclipses occur when the nodal intersection (where the moon’s orbit intersects the ecliptic) occurs near a new moon or a full moon. By definition, a lunar eclipse must occur near a full moon. This also marks the start of the solar eclipse season, with an annular solar eclipse occurring two weeks later, on June 10th.
The flight of the moon through the shadow of the earth on Wednesday May 26th. Adapted from NASA / GFSC.
A ‘super, flower, blood moon’ solar eclipse
No doubt you’ve heard the next week’s event known as the “Super Blood Moon” eclipse. That’s because the full moon and solar eclipse on Wednesday occur just nine hours after the next lunar perigee of the year, and the moon is 357,309 kilometers away. The Perigee Moon appears 33 ’28 ” in diameter during the eclipse, slightly larger than its normal 30 ‘diameter. Can you spot the difference
The circumstances for the solar eclipse on Wednesday
The penumbral stage for the solar eclipse begins at 8:47 a.m. Universal Time (you can convert UT to your local time here). However, it will still be about half an hour before you notice a slight tea-colored shade on the southeastern lunar limb. The actual action begins at 9:45 UT, when the moon enters the inner dark umber of the earth’s shadow and the partial stage of the solar eclipse begins. Totality begins at 11:11 UT and the solar eclipse occurs at 11:20 UT. Be ready for a very short solar eclipse with only 14 minutes and 30 seconds total time. The process is then reversed, with the moon leaving the umber at 11:26 UT and the solar eclipse ending at 13:50 UT.
Visibility prospects for the solar eclipse on Wednesday. Photo credit: NASA / GSFC / F. Espenak.
This is a very brief solar eclipse, in fact, as total lunar eclipses occur. In fact, next week’s total lunar eclipse is the second shortest in the 21st century: only the total lunar eclipse of April 4, 2015 was shorter with a duration of around 12 minutes. The third runner-up of the century on October 21, 2091 (mark your calendar) is approaching with a total duration of about 20 minutes.
… And maybe you won’t see the moon go away entirely. The 2015 solar eclipse was extremely bright, and many observers noted that, to their eyes, the solar eclipse never seemed to have completely hit the whole. This sparked a lively discussion about the estimated and apparent diameter of the Earth’s inner shadow umbra at the distance of the moon. Certainly the actual edge of the earth’s shadow appears as ragged and diffuse, as opposed to sharp and clear. Here’s a fun project: without paying attention to the exact contact times, try to judge which partial phases of the moon are beginning, compared to the beginning and end of totality. Were you close
Multicolored entirety. Photo credit: Dave Dickinson
Things to look out for
During the entire time, make sure that the south-western limb of the moon takes on a bright orange to dark red shimmer, the bloody “blood red” of the “blood moon”. Since this solar eclipse is barely complete, the moon should take on a light, multicolored hue, from saffron yellow near the edge to darker red near the core. This is the result of a thousand sunsets on the edge of the earth filtered into the shadows of the planet on the moon. If you stand on the moon’s surface and look back, you will see a total solar eclipse. Not all total lunar eclipses are created equal, and the color of the moon during totality depends on how deep it goes through the core of the umbra and how much particulate matter and aerosols are in the earth’s atmosphere at that time.
The Danjon scale describes the apparent color of a solar eclipse from 0 (very dark) to 4 (very light). Although binoculars or a telescope can improve vision, you can enjoy a total lunar eclipse with just one working pair of 1x Mark-1 eyeballs. You will see visual confirmation that the world is indeed round during a total lunar eclipse when the curve of our planet crosses the face of the moon.
Lunar eclipses as medieval ‘GPS’
Before the advent of accurate chronometers, lunar eclipses were useful for providing a one-time correction to your longitude at sea. Columbus claimed to have tried to find his position in the Atlantic using eclipses in 1494 and 1504, although he preferred a smaller model for the true size of the earth and was less than successful. Captain James Cook fared better and used eclipses and the lunar distance method for celestial navigation during his voyages across the Pacific to assess his position.
Stories of the Saros
The total lunar eclipse on Wednesday is part of the Lunar Saros series 121, member 56 of 84 eclipses. This is the final total lunar eclipse of this Saros, which began on October 6th, 1047 and triggered its first total lunar eclipse on July 13th, 1516. If you caught the total lunar eclipse on May 16, 2003, you saw the last member of the same lunar Saros family.
Almost all of it during the 2003 eclipse. Photo credit: Dave Dickinson.
Accept the ‘Selenelion’ challenge
Well-positioned observers on Wednesday may have a chance for a unique visual observation on Wednesday morning / evening: They can – very briefly – see the completely darkened moon and the sun over the horizon … at the same time shortly after sunrise. This is known as the Selenium Elion.
What’s going on here? Doesn’t the moon have to be opposite the sun for a lunar eclipse to work?
This happens because the shadow of the earth is not exactly the size of the moon, but is actually about three times as large. This means that the moon can linger a little in this upper shadow after sunrise but before moonset. And of course, the curvature of the planet and atmospheric refraction can further distract the apparent versus the actual observed position of the sun and moon. A fascinating study from 2018 showed that the observed and predicted sunrise and sunset times in your favorite weather app can be shifted by up to five minutes.
The line to see a Selenium on Wednesday (between line U3 and U2 on the map) runs from East Texas to Montana and western Canada and Alaska at dawn and from China and Southeast Asia at dusk. Be sure to find the flat horizon possible to perform this unique visual athletics feat. The higher the altitude, the better.
The next lunar eclipses will not occur until November 19, 2021 (a partial moon) and May 16, 2022 (the next total moon).
Cloudy or just on the wrong side of the planet to see the total lunar eclipse on Wednesday? The good folks at the Virtual Telescope Project webcast you up to date about the solar eclipse being hosted by astronomer Gianluca Masi on May 18th at (10:00 UT / 6:00 EDT).
The eclipse webcast on Wednesday. Photo credit: The Virtual Telescope Project.
Don’t miss the total lunar eclipse next Wednesday: it’s worth getting up early (or staying up late).
Mission statement: totality! The total lunar eclipse in January 2019. Photo credits and copyright: Szabolcs Nagy.
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