In the days leading up to Monday, thousands of eclipse chasers are expected to flock to a 70-mile-wide swath of land stretching from Oregon to South Carolina. This is the path the shadow of the moon will cut across the continent, traveling at more than 1,000 miles per hour, blocking out the sun.
Those lucky enough to get close to the very center line of this path of totality will be treated to about two and a half minutes of midday darkness, the disc of the moon blotting out the disc of the sun and revealing the luminous, wispy solar corona, the super-heated outer atmosphere of the sun.
But for a team of researchers from the Southwest Research Institute in Boulder, Colorado, that moment of total eclipse will be stretched out to nearly seven minutes. That’s because, using two WB-57F jets from NASA, the team will literally chase the moon shadow from Missouri to Illinois to Tennessee.
Taking off from Houston, the jets will climb to an altitude of 50,000 feet and fly in formation beneath the eclipse, using twin telescopes in the aircraft noses to view the solar corona. At that altitude, the background sky will appear 20 to 30 times darker than on the ground. And with less turbulent air, researchers hope to be able to observe minute fluctuations in the corona. This could help scientists understand why, for example, the corona, at a few million degrees Celsius, is so much hotter than the surface of the sun, which keeps to a relatively tepid 6,000 degrees—the long-standing "coronal heating problem."
In the half hour before and after totality, the jets will also take infrared images of Mercury in a first attempt to create a thermal map of the planet closest to our local star. Mercury spins slowly, a single day lasting 59 Earth days, so the dayside reaches a searing 800 degrees Fahrenheit. Scientists hope that by measuring the night side as it cools, they can learn more about the Mercurial soil, and ultimately, the process by which rocky planets are formed.