Bucket List Alert: Solar Eclipse 2017
By Eric Fleming
In August 2017, a total solar eclipse will be visible from the US for the first time in over 30 years.
In 1918, the year better known for the end of World War I and a raging influenza pandemic, a total solar eclipse traversed the United States from coast to coast. Now, 99 years later, Americans will finally get another chance to experience one of nature’s most awe-inspiring displays. On the morning of Aug. 21, 2017, a total solar eclipse will travel across the United States from Oregon to South Carolina. Along the way, it will pass over thousands of cities, towns, and parks, giving millions of people the chance to cross “viewing a total eclipse” off their bucket lists.
Dr. James Lattis is the director of UW Space Place, the outreach and education center for the UW-Madison Astronomy Department. Lattis cleared up a common misconception about the rarity of solar eclipses by stating, “The appearance of a total solar eclipse at a specific point on the Earth is the rare thing, not the eclipse itself.” To better clarify: Total solar eclipses, which occur when the moon passes between the sun and the earth and completely covers the sun, are only visible from a small area. However, partial solar eclipses, where the moon covers only part of the sun, are relatively common and can be seen across a wide area. The defining characteristic of total solar eclipses is that they are only visible in a narrow range of about 100 miles wide. The last time a total solar eclipse occurred in the United States at all was in 1979, but it has been since 1918 that the path of totality has stretched from Atlantic to Pacific. Observers will get about two minutes of totality this year.
Total solar eclipses get much more attention than the more common partial eclipses, as they are far more dramatic. When situated in a broad viewing area during a total eclipse, an observer can watch the shadow of the moon race across the landscape. Lattis likens this to “a science fiction movie.” When the shadow reaches the viewing point, shadow bands, which are light and dark bands, are painted across the landscape. This phenomenon continues as temperatures drop sharply once the area is covered in sudden darkness. At the abrupt arrival of nighttime conditions, birds and other animals behave strangely. Looking around, there is twilight circling the entire horizon. Higher in the sky, stars and even planets are visible, despite it being midday. However, the most striking part of a solar eclipse is the sight of the sun’s outer atmosphere, the solar corona.
“You can’t possibly miss a total solar eclipse. It’s probably the most dramatic astronomical experience that I can think of.” — Dr. Lattis
The surface of the sun, or photosphere, is extremely bright. The atmosphere, or solar corona, is orders of magnitude dimmer and can only be seen during a total solar eclipse. “Even in a partial eclipse that’s 99 percent covering the surface of the sun, the sunlight is still extremely bright,” Lattis says. “There’s enough of it that the atmosphere never gets dark and you can’t see the corona.” In the absence of the photosphere, the solar corona is bright and vivid. According to Lattis, in a total solar eclipse, “photographs can’t really capture the bright and dark detail.” It’s truly something that must be seen in person.
The solar corona is not just mystifying to casual observers; it still has many secrets astronomers have yet to unlock. As the atmosphere of the sun extends away from the surface, it increases in temperature, from a few thousand degrees to a few million. This is counterintuitive; generally, things get colder further from a heat source. Solar eclipses are an important time for astronomers to study why this occurs. “There is an interesting physics going on there in that plasma environment that we have yet to understand completely,” Lattis says. Although astronomers at UW-Madison are not currently participating in the ongoing research on the solar corona, they were once heavily involved, back when solar eclipses were used for a wider range of observations. Before advances in astronomy, solar eclipses were used to search for undiscovered planets near the sun, and UW astronomers partook in “eclipse-expeditions” in the early 20th century in the unsuccessful search for a planet closer to the Sun than Mercury.
Lattis has been in the path of two solar eclipses in the past. On one occasion, it was cloudy and rainy, but it still got noticeably darker during the eclipse, even through the clouds. However, that didn’t compare to the second time, when he was treated to a perfect view of the total eclipse. He describes it as “absolutely astounding,” and that “you can’t compare it to anything.” Lattis says other astronomical events, like meteor showers, “might be fairly subtle,” but “you can’t possibly miss a total solar eclipse. It’s probably the most dramatic astronomical experience that I can think of.” Lattis plans to drive down to Kansas for this eclipse and certainly is not alone in his pursuit. Many people, especially enthusiasts called “eclipse-chasers,” plan years in advance for solar eclipses. It’s not uncommon for these eclipse-chasers to book accommodations in multiple locations, waiting for the big day to determine which spot will have fairer skies. The United States’ roads and highways will make this eclipse particularly accessible; in contrast, many total eclipses are only visible from the ocean or remote areas of the earth.
It’s recommended that those interested in viewing the eclipse make travel plans as soon as possible — camp grounds and hotels near the path of totality have been filling up for quite some time. There are many public events occurring along the path of totality, and Lattis expects it to be a “huge bonanza for science outreach in the United States” Whether in the path of totality or not, it’s important to protect your eyes during a solar eclipse. Looking at the sun is always dangerous and it is only during the brief period of totality that it is safe to look at it unfiltered. In Wisconsin, there will be no period where it is safe to view the eclipse directly. However, there are ways to safely observe a partial eclipse. Sun viewing filters, number 14 welder’s glasses, or pinhole projection devices can all be used to observe the partially-eclipsed sun. The UW Space Place recently ordered several thousand sun-viewing filters in anticipation of local demand. Lattis also advises against using equipment to view the sun; concentrated solar rays can easily damage cameras, telescopes, and binoculars.
The 2017 “Great American Solar Eclipse” promises to be a breathtaking sight. Anyone who is able should try to witness it. But fortunately for those unable to get to the path of totality this August, the United States will be graced by another total eclipse relatively soon, in 2024. However, as the experience of Dr. Lattis shows, it’s a good idea to plan to attend both. Astronomers can guarantee when and where a total solar eclipse will occur, but they can’t guarantee it won’t be cloudy.
