Artificial coronagraphs in telescopes block not only the sun’s bright light but also the innermost section of the corona to minimize risk of damaging or oversaturating imagers and spectrographs.
“Some people mistakenly think that we can see the corona as well from space as we can from the ground, but the whole region that we see at an eclipse so well and in such detail in ordinary light is not visible from any spacecraft,” said Pasachoff, who has trekked across the planet to experience 65 previous total solar eclipses.
“The so-called coronagraphs that are aloft hide more than the first inner radius of the sun, leaving a whole region that’s just for us to study during an eclipse,” he added. “So only every 18 months or so somewhere in the world can we get a complete picture of the sun, as it is on that day.”
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Pasachoff plans to be in Salem, Oregon leading one of the biggest organized science projects to observe the eclipse, with 25 family members, eight students, 60 colleagues, astronomers, and tourists, and dozens of telescopes and instruments to study the corona.
His work is among dozens of such science investigations taking place across the country, including a citizen science effort backed by the National Science Foundation, NASA, and other organizations to photograph the corona using 60 identical telescopes stationed at regular intervals along the so-called “path of totality,” the 70-mile wide lunar shadow that will race across the country in 90 minutes during the Aug. 21 eclipse.
The aim of the Citizen Continental America Telescopic Eclipse project, or Citizen CATE, is to produce a 90-minute movie of the mysterious lowest layers of corona.
“At any one site you can only see the corona during totality for maybe two minutes,” said lead scientist Matthew Penn, a Tucson, Arizona-based astronomer with the National Solar Observatory. “What we’d like to do is to study the corona for a much longer period of time, and by stringing together a network of sites and merging that data, we’ll be able to make a movie 90 minutes long showing the corona.”
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Other scientists will be aboard National Science Foundation and NASA aircraft to look at the corona in infrared and other light without having to contend with obscuring clouds or atmospheric distortions. And next year, NASA plans to launch the first spacecraft that will directly sample the sun’s corona.
The recently named Parker Solar Probe (formerly known as Solar Probe Plus) will measure plasma, electrons, protons and ions and determine their velocities, densities and magnetic fields. The information not only should help physics unravel the inner workings of the sun’s corona, but illuminate the power source for the solar wind, which is a continuous stream of high-energy particles that have enough speed to escape the sun’s immense gravitational pull.
But science is not the only, or even the main, reason to look at the sun during the eclipse. During totality it is perfectly safe — and highly advisable — to shed your protective safety glasses, which are needed during even a 99 percent partial eclipse, and see the corona.
“We actually live in the outer atmosphere of this star and we are seeing that with our unaided eyes,” said NASA’s Guhathakurta. “It’s our connection to not only our parent star but to the cosmos, our universe in a big picture way.”