On August 21, 2017, many across the United States will be looking up, hoping to catch a glimpse of a rare total solar eclipse. Cities from the coast of Oregon to the beaches of South Carolina are hosting festivals and throwing viewing parties to celebrate this event. But it's more than just a cool light show brought to us by Mother Nature. Scientists are coming from around the world to study this eclipse in hopes of unlocking more truths about our universe.
For David Sliski, a Graduate Student of the Physics and Astronomy Department at the University of Pennsylvania, where he specializes in the detection of exoplanets, this total solar eclipse is providing an opportunity to image the sun.
"Studying the behavior of our sun allows us to test models that can help answer other questions about the universe. If we can understand our star well,” says Sliski, "we can extrapolate our knowledge of the Sun to better understand how stars behave. In turn, that should also help us understand the habitability of planets that orbit other stars.”
Professor. Cullen Blake and David Sliski in southern Arizona at the dedication of their new telescope MINERVA-Red, a telescope dedicated to the discovery of planets orbiting the nearest low mass stars! — Photo courtesy of David Sliski
Sliski is heading to Salem, Oregon to participate in one of the largest organized scientific expeditions to study the sun and the sun’s effects on Earth at the eclipse. The expedition is being led by Professor Jay Pasachoff of Williams College and the Chair of the International Astronomical Union’s Working Group on Solar Eclipses. This will be Pasachoff’s 66th solar eclipse.
I recently sat down with Sliski to discuss the upcoming solar eclipse and what the everyday person should know in order to enjoy the event with a deeper level of understanding and scientific curiosity.
What is a solar eclipse?
A solar eclipse occurs when the moon’s orbit passes between the sun and the Earth, casting a shadow on the Earth. This can only happen when the moon is in a new moon phase. But don’t expect to see a solar eclipse every new moon.
“This is because the orbit of the moon is inclined to the orbit of the Earth,” explains Sliski. “Only once every 18 months do the two line up to get an eclipse of the sun. Also, the moon’s orbit isn’t round so it can sometimes be too far away, causing the moon to not completely block out all of the sun’s light, causing an annular eclipse.”
What type of eclipse can be seen across the U.S., Source: NASA — Photo courtesy of Janet Loehrke, USA TODAY
Where will you be able to see the eclipse?
The umbra, where the sun will be completely eclipsed, will stretch continent-wide from Oregon moving southeast through South Carolina. The path of totality is a 70-mile wide area where you can see the full eclipse. 12.2 million people live within the area of totality and another 200 million live within a day’s drive to these areas. So about two-thirds of the nation’s population should have an opportunity to see a total solar eclipse.
Outside of that area, people will be able to see a partial eclipse. Regardless, the majority of North America will be able to see some portion of this solar eclipse, weather permitting of course.
How rare is a solar eclipse?
The last time a total eclipse could be seen within the United States occurred in 1979. But what makes this eclipse so rare is the fact that it is continent-wide and occurring solely within the United States. That hasn’t happened since 1918.
Statistically speaking, experiencing a total solar eclipse in your hometown only happens once every 375 years, according to NASA.
How long will the eclipse last?
“The entire event will last anywhere form 2 to 3 hours,” says Sliski, “but the full eclipse only lasts about 2 minutes and 40 seconds.”
According to NASA, the longest eclipse will take place in Carbondale, Ill., where they’ll experience the eclipse for 2 minutes and 43 seconds beginning at 1:20 p.m. CDT.
2006 total solar eclipse as seen from Egypt – Kodachrome 64, 400mm Nikkor f/5.6 with 2x teleconverter, Nikon F2SB camera — Photo courtesy of Alan P. Sliski
Will the conditions on Earth change during the solar eclipse?
Expect the weather and animal behavior to change quite suddenly. Winds will increase, the temperature will drop and birds will stop singing and behave as if night has fallen. Gravity on Earth will also be affected mildly. During the solar eclipse, those within the path of totality will be 1.7 ounces lighter, according to NASA.
To help scientists collect data of how plant and animal life react to the solar eclipse, download the iNaturalist app, create a profile, join the Life Responds project and document your location and observations during the eclipse!
What exactly are scientists looking for during the solar eclipse?
To understand what scientists are looking for during the eclipse, it’s best to understand the anatomy of a star. “At the center of our sun, we calculate core temperatures to 15 million degrees Celsius,” explains Sliski.
That’s where you have nuclear fusion, where hydrogen is turned into helium. As you go away from the core of the star it gets cooler. The surface temperature is about 5,500 degrees Celsius. Outside of that is the chromosphere, which, for us on Earth looking at our star, is best visible during a total solar eclipse. The corona can reach temperatures of a million degrees Celsius. We are still trying to figure out what mechanism in the star drives plasma to reach such high temperatures away from the surface of the sun.”
An illustration of the structure of the sun — Photo courtesy of Kelvinsong
And what answers does the corona hold?
“The sun influences our weather,” Sliski says. “It goes through these 11-year solar cycles. Every 11 years, we observe an increase in solar activity and sun spots. Think of a hurricane on Earth. Instead of water storms, you have magnetic storms and instead of being the size of a state, they can be larger than the diameter of the Earth!"
Our goal is to measure how these magnetic fields of the sun vary with time. We want to understand how sun spots correlate with coronal activity. A total solar eclipse gives us an unusual opportunity to measure the entire corona and compare it to recent measurements of sun spots.”
Wait...our sun has 11-year “solar cycles”?
“Yes! It’s like a heartbeat. If something has a lifespan of 10 billion years, 11 years is quite short," says Sliski.
"While we have seen evidence of very low activity in the past, we are less sure how that affects the weather here on Earth. By improving our models of how the sun works, we can better understand how Earth’s climate is affected by changes in the sun.”
Where to buy safe eclipse viewers — Photo courtesy of USA TODAY Network
How can the average person watch the solar eclipse safely?
Wear eclipse glasses. Do not look at the partial solar eclipse without them. The only moment you don't need eclipse glasses is when the Sun is completely eclipsed by the moon. Otherwise, you need to make sure your eyes are protected. Eclipse glasses cost around 1 dollar, but be sure you purchase only certified filters.
NASA also has nifty instructions on how to make your own pinhole projector.
Are there any ways to help in this scientific initiative?
Along with joining the iNaturalist app and observing the changes in animal behavior during the eclipse, NASA has plenty of Citizen Science programs for “amateur astronomers and lifelong learners” to participate in. There are programs ranging from basic observations all the way to partnerships with NASA and university scientists. Check out NASA’s Citizen Scientists for more details on programs you can participate in.