While millions of astronomy enthusiasts chase the moon’s shadow on the ground during the August 21 total solar eclipse, four NASA personnel are going to have front row seats. Two pilots and two technicians will race the big black spot at 50,000 feet, well above any cloud cover. And at 400 mph, they’ll be able to stretch their time in the shadow to three minutes, compared to two on the ground.
They’re not just up there for the view. The aircraft, two 1960s vintage WB-57F jets that NASA frequently dispatches for high-altitude research, will carry instruments to help scientists study the solar atmosphere. At cruising altitude, the sky will be 20 to 30 times darker than on the ground, enhancing the details in the sun’s atmosphere—and allowing for pictures in the greatest detail yet.
Typically, solar scientists simulate eclipses with special equipment designed to block the sun, called a coronagraph. But the small disk, usually mounted in front of a telescope, can’t fully overwhelm the sun’s brightness. The moon can, though—which is why people have flown telescopes during eclipses before. “But this will be the highest quality observation of this type made to date,” says lead researcher Amir Caspi, a senior scientist at Southwest Research Institute in Boulder, Colorado. “The resolution and the frame-rate we’ll be able to achieve will provide new insights into how the sun works.”
Flying in tandem on either edge of the shadow’s 70-mile girth, the planes’ paired data will effectively stretch totality to a full seven minutes. They could have stretched it further, but with diminishing returns: “You can fly at supersonic speeds to extend totality,” says Caspi. “The Concorde managed to stretch it to 74 minutes when they did their eclipse flight, but that also generates a lot of distortion in the airflow around the airplane.”
This flight’s relatively low speed will ensure minimal turbulence for the instruments, which are set on moveable gimbals to track the sun as the jets pitch and roll. They’ll use cameras called AIRS/DyNAMITEs, initially developed to track the Space Shuttle during launches in the wake of the Columbia disaster. Data will be recorded onboard the aircraft but also transmitted through ViaSat satellite downlink for live broadcast on NASA’s site.
That footage will help answer a few solar conundrums. The outer atmosphere of the sun, strangely, is dramatically hotter than its surface—like, millions of degrees hotter. There are two competing theories why: One says that the magnetic field can have so-called Alfvén waves moving through it, transmitting the sun’s energy into the outer atmosphere, while another holds that small explosions called nanoflares might be releasing heat. The flight’s high-resolution infrared video should be able to detect slight wave motion in the corona—the sun’s atmosphere, which is usually overwhelmed by the star’s surface brightness—allowing the scientists to determine the strength and sizes of the waves, along with their potential influence on temperature.
The equipment may also reveal the nanoflares, which nobody’s technically ever seen. If they do finally appear, they could help explain another solar quirk: the surprisingly uniform pattern of the corona’s arches and streaks. “It has loops and fans and smooth, well-organized structures, but our images of the surface and our computer models, suggest a turbulent, boiling environment, so the corona should look like a tangled, snarled mess,” Caspi says. “The corona looks like it’s been combed, so we want to know why it’s combed corona and not bedhead corona.”
That’s all well and good for the solar scientists. But understanding the sun has applications back on Earth, too. “Studying things like these two factors and the solar flares and the coronal mass ejections we can also see during eclipses teaches us about weather hazards,” says Caspi—you know, like the possibility of a solar flare disrupting the power grid or messing with satellites. And any solar energy system that impacts Earth will impact other planets around other stars—which means these discoveries could influence the search for habitable planets. “We may find a planet where the temperatures are right for life, Caspi says, “but if it’s getting blasted by X-rays all the time, you’re not going to find life—at least, not on the surface.”
Now, that’s just what the flights will focus on for three minutes. In total, they’ll be airborne for several hours as they cut a path from Houston’s Ellington Field near NASA’s Johnson Space Center through Missouri, Illinois, and Tennessee. So for 30 minutes before and after totality, during the partial phases of the eclipse, the instruments will zoom in on sun-adjacent Mercury, which is typically tough to image because it gets washed out by sunlight.
In that hour, they’ll be looking for information about how Mercury’s temperature varies across its surface. The red planet rotates much slower than Earth, resulting in a dramatic fluctuation in surface temperatures—from 800 degrees Fahrenheit in the middle of the day to 300 below zero at night. (One day on Mercury equals 59 Earth days.) Infrared cameras will assess the surface temperature across the surface to see how quickly it cools, which will reveal its composition in greater detail than previous attempts using X-ray imaging.
This is just one of 11 research projects—mostly ground-based—that NASA is funding in conjunction with the eclipse, but it promises to generate perhaps the most dramatic results. It’s just a pity that the airplanes only hold two people. “It’s my first eclipse, but I’ll be watching it from a monitor in Houston,” Caspi laughs.