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University Gazette

The University of North Carolina at Chapel Hill

Illuminating facts about the coming solar eclipse

Wearing ISO-certified solar eclipse viewing glasses, Chris Clemens stares at the sun, safely.

On Aug. 21, the continental United States will experience a total eclipse of the sun. The darkest shadow of the moon will travel from Oregon to South Carolina in about 90 minutes. The 70-mile wide path of the shadow is called the “path of totality.” Only the southwest corner of North Carolina (including Murphy, Cullowee and Brevard) lies in the path, but the rest of the state – including Chapel Hill – will experience almost complete darkness for about 2.5 minutes in mid afternoon, about 2:43 p.m. We checked in with stellar astrophysicist and astronomer Chris Clemens, senior associate dean for natural sciences, to find out more.

What is an eclipse?

An eclipse is the alignment of three bodies: sun, moon and Earth. And when the moon comes between the sun and the Earth, you can see the moon blot out the whole sun. In Chapel Hill, we’ll see the moon blot out most of the sun.

Why is this one special?

Scientifically speaking, it is no more special than any other eclipse. It’s unusual to have one go across the United States all the way, so there are a lot of potential places to see it. This is going right through the heartland.


How can you watch an eclipse safely?

In Chapel Hill, you should not look at the sun without glasses specifically designed for direct solar viewing. That would not be drugstore sunglasses. That would be an ISO-certified direct solar viewing pair of glasses. The paper ones are not very expensive and they’re perfectly good, but look for the certification. With those on, it is safe to stare at the sun and without those on, it is not safe. Even if it feels comfortable to look at that sliver of light from the sun, do not do that without your glasses or you will have burned spots on your retina for the rest of your life. I cannot emphasize that enough.

This map shows the path of totality for the Aug. 21 solar eclipse.

What will you see?

If you can travel to a place where the eclipse is total, you should watch right at the moment when the sun disappears completely. There will be a little sliver and then a tiny point of light that looks like a diamond ring almost. At that moment, you may see the crescent of the sun broken up into tiny pieces, like beads. We call them Bailey’s Beads. That’s because there are mountains on the moon that obscure parts of the sun before other parts. It’s really a proof that the moon is not perfectly spherical. If you look, you can see Mars, Venus and Mercury in the daytime because once the sun’s covered, the planets will come out. You’ll see stars and you’ll see planets. On eclipse day, you will see projections of the sun everywhere – under trees and all around.

Where will you be watching the eclipse?

Somewhere in South Carolina and I’m hoping for good weather. I’m going to have my ISO glasses and my binoculars. Binoculars are dangerous and only useable without special filters during the total portion of the eclipse when stars and planets become visible, but I’m not going to hand the binoculars to my kids. They might vaporize part of their retinas when the sun reappears.


What is it like to be in the path of totality?

You’ll see kind of a curtain of darkness in the west and then a shadow moving at very high speeds will sweep across you. It’s not like the shadow of a cloud. You’ll feel almost engulfed by darkness. [The path of totality is also the only place you can safely view the total eclipse without special glasses.] What are the effects of an eclipse? You will hear birds and crickets, just as if it were dusk or nighttime. You’re viscerally aware that something strange is happening. And you might feel a sense of ominous dread, or, if you are an astronomer, a sense of elation.