Total Solar Eclipse Shines Light On Science

Aug 18, 2017

On Monday the long-anticipated “Great American Eclipse” will cross the country coast-to-coast from Oregon to South Carolina. Scientists will watch the sun vanish behind the moon using telescopes on the ground and from weather balloons and planes. But what are they looking for? KNAU’s Melissa Sevigny spoke with Lowell Observatory astronomer Gerard van Belle about science that can only be done during a total solar eclipse.

Credit NASA

Melissa Sevigny: This particular eclipse is crossing the nation coast to coast; tell me what that looks like.

Gerard van Belle:  They’ll be a spot that will sweep across the nation, where the entire face of the sun gets blocks out by the moon, and in that path—the path of so-called totality, where you have a total eclipse—you’ll get the sun completely blocked out. And you can see the stars come out, you can see outer reaches of the sun that you don’t normally see, that are much fainter than the actual surface of the sun, and you’ll be able to feel the temperature drop. This will be a spot of shadow that will hit the Oregon Coast in the morning and will sweep across the nation in about an hour and half.

The path of totality
Credit NASA

What can scientists learn about the Sun during a total solar eclipse that you can’t normally learn?

So the sun has outer regions that are very tenuous and faint and not very well understood, because if you look in the direction of the sun oftentimes that part of the sun just gets washed out by the brightness of the sun itself…. But when you have the special configuration of the earth and moon and sun in the case of a total eclipse, the photosphere of the sun, the shining surface of the Sun, gets blocked out by the moon, and then these outer dim areas pop out. They tell us a lot about the processes that are going on just above the surface of the sun, it much the same way you have weather going on over the surface of the solid Earth.

OK, so the sun actually has weather?

It does! It does. One of the most obvious things associated with space weather is this idea of how flares from the sun can throw bursts of energy and material into space and sometimes in the direction of the Earth. … It is fascinating and also mildly terrifying to think about what an event like that would do to us now that we’re so much more reliant on satellites and cell phones and TVs and all this technology around us which would probably go silent for a few days in the middle of something like that…. You’d have to go back to playing Scrabble with pen and paper rather than Words with Friends.

You mentioned earlier when the moon blacks out the Sun, this is really the only time we can see that outer atmosphere of the sun. What does that look like?  

The sun's corona during a total solar eclipse
Credit M. Druckmuller

It looks a lot like flowing tendrils of hair, almost, on the sky, and it can be quite dramatic in terms of its appearance, how big it is on the sky, and it’s one of those things, where, it’s very interesting when you pull back the curtain and suddenly see something that’s been there all along, and yet we haven’t realized that because it’s been basically blocked out by the bright central sun.

So you’re heading for Oregon for this total solar eclipse, what are you most looking forward to?

Well I’m doing a road trip, with my family in an RV, I’m most looking forward to us just making it. I’m looking forward to the adventure of eclipse itself…. The observatory, as you know, is having a big event up in Madras Oregon, we’re taking over the high school up there, we expect many thousands of people to come join us for that. So it should be a lot of fun.

Safe travels and thanks so much for speaking with me.

Thank you very much.