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Solar eclipse: No totality in Boro, still fascinating

Partiality means no safe moment to look at sun unprotected

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Solar eclipse: No totality in Boro, still fascinating

Georgia Southern Physics Chair and Planetarium Director Clayton Heller watches a scene from "Totality," a planetarium show about solar eclipses.


People who expect to see the full effects of a total solar eclipse in Statesboro on Aug. 21 will be disappointed, but the eclipse tracing a rare transcontinental path remains fascinating even to astronomers, says Professor Clayton Heller, Ph.D., director of the Georgia Southern University Planetarium.

Heller also chairs the university’s physics department. In research, he specializes in the structure and evolution of galaxies, so the interplay of the sun, moon and earth in an eclipse might seem relatively mundane. But Heller plans to drive to Columbia, South Carolina, which is in the path of the eclipse’s totality, to experience it in all its glory. He traveled to Mexico for a total eclipse about 20 years ago and describes what it’s like in enthusiastic detail.

“When you go into totality, I mean, it’s like nothing you’ve ever experienced before, if you’ve never seen one,” Heller said. “You have to remember it’s the middle of the day, it’s usually the hottest point of the day, and all of a sudden it gets dark, and it goes quick.”

Before the brief time of totality, the moon will be slowly encroaching on the apparent disk of the sun for a much longer period. But when even a sliver of the sun is still visible, the sunshine remains quite bright, until the glow at last resembles that on a cloudy day, he said. Then, suddenly, darkness arrives. Over central South Carolina, the totality is expected to last about two and a half minutes.

“Then it gets really dark, the temperature drops because it’s mainly solar heating, all the birds go quiet because they’re like shocked that the lights  went out, and then all of the  stars  come out, which it’s the middle of the afternoon,” Heller said.

 

Nothing like totality

But don’t expect that in Statesboro on Aug. 21.

“It’s not going to be total here, and the sun is so bright that even if a little bit is showing, it’s just not the same thing whatsoever,” Heller said. “It will look maybe like it’s a cloudy day or something, if you didn’t know what was happening.”

As the sun will appear from Statesboro, it will obscured at most 97 percent, reaching that maximum at about 2:44 p.m. Eastern Time. These and other numbers cited here for the eclipse’s timing are derived from the U.S. Naval Observatory’s online eclipse computer, which uses 24-hour Universal Time. See “Data Services” at http://aa.usno.navy.mil.

From the moment when the moon begins to pass in front of the sun until the trailing edge leaves the sun’s disk, or photosphere, the eclipse will last almost three hours. The Naval Observatory gives a start time of roughly 1:13 p.m. and an end-time of about 4:08 p.m. specific to Statesboro’s longitude and latitude.

A couple of factors make this a once-in-a lifetime eclipse for Americans. It will be the first total eclipse passing coast-to-coast across the United States since 1918, and the first since 1776 where the only places the totality is visible from land are within the continental United States, Heller said.

The path will stretch from Salem, Oregon, east-southeastward through America’s heartland to Charleston, South Carolina. The umbra, the central portion of the moon’s shadow, will form a cone pointing downward to a region about 70 miles wide. This swath, where the dark totality will occur, passes through the heart of South Carolina.

But except for the corner of the state northeast of Athens, eastern Georgia, while tantalizingly close, will not be in the umbra, but in the penumbra. This is the wider part of the moon’s shadow, coning outward, where totality will never arrive.

Within the path of the umbra, the peak experience will be shorter than in some total eclipses, where totality can last as long as seven to eight minutes, Heller said.

 

Corona and relativity

But the brevity doesn’t prevent the eclipse from being of interest, even to serious astronomers. By blocking light from the photosphere, the moon makes visible the sun’s faintly glowing corona, which is actually larger than the photosphere, Heller said.

“It is important for astronomers to be able to really look at the outer part of the sun’s atmosphere,” he said. “Otherwise, you really need to do it from space. There are special solar telescopes that occult the disk, but they’re just not quite the same.”

Observations during a total solar eclipse, in 1919, provided the first confirmation of Albert Einstein’s general theory of relativity, Heller noted. Stars viewed near the sun, where they would usually be invisible in daylight, appear shifted from their measured positions, proving Einstein’s prediction that light is affected by the gravity of massive objects.

The corona, and solar prominences or flares if these happen to coincide with the eclipse, are also responsible for some of the more interesting visual effects within the path of totality.

“They’re a beautiful color, a beautiful – like, violet,” Heller said. “It’s hydrogen alpha emission is what it is. That’s a color like fluorescent light. It’s not a color that you ever see in nature, normally, but there it is. That’s nature.”

 

Diamond and beads

Other effects noted for their beauty include  the “diamond ring” that occurs when the last sunlight flares out on one side of the moon before totality, and Bailey’s Beads, when light breaks through valleys at the edges of the moon.

But don’t expect these in Statesboro, even with 97 percent obscuration, Heller said.

In the umbral path, such as in central South Carolina, there will be a couple of minutes after the Bailey’s Beads disappear when removing eclipse protection glasses for a better look would be safe, he said, but not here.

“You have to be very careful,” Heller said “You should never be looking at the sun with your bare eyes.”

Individuals and school groups can still have useful learning experiences observing the moon pass over the sun in the partial eclipse here, he said.

“You can get eclipse glasses, but they need to be the right type of glasses,” he said. “You can’t use sunglasses, for instance.”

Acceptable eclipse glasses carry the international safety designation ISO 12312-2. NASA’s special website, https://eclipse2017.nasa.gov, carries a list of approved manufacturers and sources. See the site’s “Safety” tab. There is also an “Education” tab and instructions for making various pinhole projectors for observing the sun while looking away.

Old, bent or scratched safety glasses should be thrown away, because these could allow damaging light through, Heller said.

 

Shows and a caravan

The Georgia Southern Planetarium will present its eclipse show, “Totality,” twice on Wednesday and five times on Friday, but all shows are already “sold out,” said Planetarium Coordinator Dillon Marcy. The planetarium is distributing eclipse glasses for a $1 donation to attendees at the Friday shows, but he has only 250 pairs of glasses, or 50 for each show, with 67 people already signed up for each of the five shows.

Not surprisingly, some Georgia Southern students will travel to experience the totality. The College of Science and Mathematics, or COSM, has a truck going with cars following.

“I don’t know how many people are going to go, but we’re essentially starting a caravan and we’re going to make our trek up to South Carolina Monday morning,” said Marcy, who graduated last year with a bachelor’s degree in physics and astronomy.

The caravanning students have an open area where they have permission to observe the eclipse, Heller said. Individuals making their own journeys should expect traffic, have a known destination and not plan to park on the side of the roadway, Heller said. Also check the weather and choose your destination accordingly, he advised.

Herald reporter Al Hackle may be reached at (912) 489-9458.

 

 

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