Monday, August 21, will bring us the first coast-to-coast total solar eclipse in the United States in 99 years. While not incredibly uncommon generally—total solar eclipses can be seen from Earth every couple of years—this one is special to us, as it will cut diagonally across the entirety of the United States.
Knowing the significance of this upcoming eclipse is one thing, but knowing the science behind it is another. For that, Twin Cities Geek turned to Evan Tyler, a PhD candidate researching space physics and the outreach coordinator for the Minnesota Institute for Astrophysics (MIfA) at the University of Minnesota. “A solar eclipse happens when the orbit of the moon lines up so that it moves directly between Earth and the sun, from our line of sight,” he explained. “The moon orbits the earth about every 27 days, but we don’t see a solar eclipse every 27 days on the new moon. This is because the moon’s orbit is tilted a few degrees compared to the line of sight between the earth and the sun. Thus, during most new moons, the moon isn’t quite in the right position to cover the sun, so the earth will only experience an eclipse two to five times per year, and a total eclipse happens even less often.”
For most Minnesotans, the moon will be covering a little over 80 percent of the sun at the peak of the eclipse—not enough to darken the sky too much or really weaken the sun’s energy. Yet for those looking to indulge their cosmic curiosities with the best local views of the eclipse, be sure to check the weather forecast for clear skies and make your way southwest of the Twin Cities for higher percentages of occultation (coverage). As explained by Dr. Lindsay Glesener, professor and solar physics researcher at the University of Minnesota, “the farther southwest you can get, the better, so our view here in Minneapolis will be better than the one in Duluth. You’d probably buy yourself a couple percent more of occultation with every hour southwest you drive, but the occultation won’t get to more than about 92 percent even in southwest Minnesota.”
Whether you’re planning a full-on road trip to view the eclipse in totality or simply hoping to catch a glimpse by looking up wherever you might be at the time, proper protection is imperative. Regular sunglasses definitely won’t cut it, so look for specifically designed eclipse glasses or eyewear specifically made for looking directly at the sun. For specifications, NASA’s eclipse safety page details criteria for safe eclipse glasses as well as verified manufacturers.
If totality—or full coverage—is your goal, you may have to venture outside of of the state. Bill Glass, a member of the Minnesota Astronomical Society someone who could be described as an “experienced eclipse chaser,” has traveled to the likes of Mexico, Aruba, Bolivia, Zambia, Kenya, Libya, the Faroe Islands, Turkey, India, Mongolia, China, Australia, and Easter Island to view and record total solar eclipses. For this one, however, he’s able to stay a little closer to home. “Personally, I prefer to be away from cities and in a location that permits seeing a large chunk of the sky so that I can see the effects of the changing light levels,” he says. “In general, the western USA offers better weather prospects than the eastern half of the country; however, there are plenty of opportunities along the path of totality to catch some spectacular views.”
Apart from proper eyewear, timing is everything. While the complete event lasts throughout most of the day on August 21, the best views will be brief. “The max occultation time just happens to be very close to solar noon—the time at which the sun is highest in the sky,” explained Dr. Glesener, who will be viewing the eclipse at a Solar Physics Division meeting of the American Astronomical Society in Oregon. For us here in Minnesota, we can expect max occultation at about 1:06 p.m. CDT.
For more general information on the eclipse, NASA’s eclipse outreach site contains interactive maps and calculators, viewing tips, and detailed facts and figures. If you’re interested in taking a more proactive, participatory approach, check out the eclipse Megamovie Project, which will be gathering images from over 1,000 volunteer photographers in an effort to stitch together an “expanded and continuous view of the total eclipse as it crosses the United States.” More locally, if you’d like to meet fellow stargazers and eclipse enthusiasts, the Bell Museum will be hosting a pre-eclipse block party on Sunday, August 13, at the University of Minnesota.
The next major solar eclipse visible from United States won’t be for another seven years (2024), so it’s worth making a point not to miss it this time around. While many people won’t be able to travel in the path of totality, we still have the opportunity to witness one of the countless visual wonders the cosmos has to offer. Let’s all take some time, grab some eclipse glasses, and look up this August 21.