On August 21, 2017, a 70-mile band spanning the continental United States was treated to a relatively rare celestial event: a total solar eclipse. In a total solar eclipse, the new moon fully covers the sun, darkening the sky and making the stars and planets visible during the day. The band in which the total solar eclipse was visible stretched from Oregon to South Carolina—the first American coast-to-coast eclipse in nearly 100 years. (The last eclipse in the US was in 1979, but it touched only a few states in the northwest and did not span the whole country.)
“A total solar eclipse is way, way better than a partial solar eclipse or a lunar eclipse,” says Astronomy Professor Joel Bregman. “Often you’ll see prominences from the sun, which are long loops of ultra-hot plasma extending away from it. You can even see the shadow made by the moon approaching at supersonic speeds if you have a good view toward the west.”
This year, in the band of totality, the sun will be completely blocked by the moon. During the less thrilling (and more common) annular eclipse, the moon is farther away from the earth and does not fully cover the sun.
A solar eclipse happens when the moon, in its orbit around the earth, moves between us and the sun, which in turn casts a shadow on the earth. The middle of this shadow is where the total solar eclipse happens; suddenly, daytime feels like night, and you can see stars and planets twinkling in the distance. During those few minutes, the sun appears to be a thin, glowing halo around the moon. But it’s not just the short period of totality that is so striking: Bregman says the hour and a half preceding and following the eclipse, when the moon is only partially blocking the sun, is well worth experiencing, too.
Totality lasted the longest near Hopkinsville, Kentucky, whose population of 31,000 was expected to temporarily swell to over 200,000 on the day of the eclipse.
“You see a 360-degree sunset around every horizon and notice that the temperature has dropped 15 degrees,” says Bregman. “Leading up to totality, birds go home to roost, cows head to the barn, and evening insects come out, even though it’s the middle of the day.”
A solar eclipse is so sublime that millions of eclipse chasers were expected to travel to locations within the band of totality to see it. Most places in the United States, including here in Ann Arbor, were able to see a partial eclipse, but only those within a narrow belt from Falls City, Oregon, to Silverstreet, South Carolina, were able to see the full solar eclipse. Some larger cities, like Nashville, Tennessee and Lincoln, Nebraska were also within the path of totality, and were planning events to celebrate.
Astronomy Professor Mario Mateo planned a 760-mile, six-day bicycle ride from Ann Arbor to Owensville, Missouri, to view the eclipse.
Bregman was a big proponent of experiencing this year’s solar eclipse, and he has a long history of enthusiasm for the event: He began studying eclipse tables as a child and traveled to Prince Edward Island in Canada to see his first total solar eclipse in 1979. He planned to be at U-M’s Camp Davis on August 21, because the location is drier this time of year and therefore ideal for viewing the eclipse. Clouds can obstruct one’s view, he says, so be ready to move if you have to.
One final piece of advice for would-be eclipse chasers: Be sure to purchase a cheap pair of protective eyewear, because looking directly at the sun can permanently damage your eyes. (You can take them off for the minute or two of totality, but be sure to put them on during the partial phases.) And of course, most importantly: Savor this once-in-a-lifetime celestial treat.