Partial Solar Eclipse Expected for South Dakota

Aug 3, 2017

The first total solar eclipse to span across the United States in 99 years takes place on August 21st.
Michael Dowding is an instructor of physics at the South Dakota School of Mines and Technology. He explains how a solar eclipse happens.

“The sun and the moon are all in alignment with one another, in the case of an eclipse, that’s the only condition you need. So, that’s both lunar and solar eclipses…is that you have to have the three aligned together. But, a solar eclipse is going to happen when the moon positions itself between the earth and the sun and the effect is that we start to see the moon blocking out the sunlight that’s coming from the Sun…the moon will cast a shadow over the surface of the Earth and passes over a relatively small part of the Earth, which makes it difficult for so many of us to view,” Dowding says.

The path of totality, or where 100% of the sun is covered up by the moon, cuts through central Wyoming and into Nebraska -- missing South Dakota. Dowding is taking a group of physics students to Nebraska to be in the path of totality.  Areas expecting a total eclipse span from Oregon to South Carolina. NASA says many areas along the route will see the eclipse for about 2 to 2 and a half minutes.

Nathan Grau is an associate professor of  physics at Augustana University in Sioux Falls. He says the State is still expected to see a significant partial solar eclipse.

“All of South Dakota will see a substantial partial eclipse. So, again out in the Southwest it’s probably 95 to almost 100% eclipsed. In Sioux Falls, Vermillion is more like 95 percent and up in Aberdeen it’s about 90 percent…which definitely is the largest partial eclipse we’ve seen in quite a long time in the State, ” Grau says."

Grau says NASA has an interactive map showing how much of the sun is set to be eclipsed. He says the next solar eclipse takes place in 20-23, but it passes from Oregon to Texas and misses South Dakota.  Grau says there are several explanations for why eclipses happen in different places.

“There’s lots of motion happening. The rotation of the Earth is one. There’s the fact that our rotation axis is tilted 23.5 degrees compared to the way we orbit the sun…that’s the thing that causes our seasons. There’s the fact that the moon’s orbit is tilted and doesn’t orbit in the same plane that the Earth does around the Sun. And so, all of those factors together make each eclipse sort of unique,” Grau says.
NASA says the 20-23 eclipse is annular, or when the Moon is too far away from the Sun to completely cover it. The next total solar eclipse is set for 20-24. The path for this also misses South Dakota but will stretch from Texas to Maine, cutting through parts of the Ohio Valley and the Great Lakes.