NASA will fly two of its highest-flying aircraft from Houston, Texas, to race along with the moon’s shadow during April 8’s total solar eclipse in North America. In doing so it will extend totality from 4 minutes 26 seconds to 6 minutes 22 seconds. The experiment will help scientists learn more about the sun’s atmosphere and how it affects Earth’s climate.
Highly Complex
The space agency will provide two of its WB-57 high-altitude research aircraft to capture images of the totally eclipsed sun’s corona and its hotter outer atmosphere. Compared to the sun’s surface, the corona is a million times hotter and a million times dimmer in the wavelengths of light our eyes can perceive.
This highly complex part of the sun’s atmosphere—only visible during the short totality phase of a total solar eclipse —produces the solar wind, which creates aurora but can also cause problems for satellites and electrical power grids.
Fly In Tandem
The planes will fly in tandem into the path of totality, a 115 miles-wide, 9,200 miles-long track that strikes land at northwestern Mexico, crosses the U.S. and southeastern Canada, and exits for the Atlantic at Newfoundland. As they enter the moon’s dark central shadow, the planes will be traveling at 400 knots, which is about 460 miles (741 kilometers) per hour.
That’s about a quarter of the speed of the moon’s shadow, which over Mazatlan, Mexico—where the plane will enter—will be traveling at about 1,500 mph (2,500 kph). Although the planes can’t keep up with that speed, counteracting a quarter of its speed will extend totality by a quarter. The next total solar eclipse that will last anywhere near that long is a 6 minutes 23 seconds totality near Luxor in Egypt on August 2, 2027. However, there are other reasons NASA needs to get as close to space as possible.
Track The Sun
The WB-57 aircraft has a camera and telescope system on a stabilized two-axis ball turret—which will act much like the gimbals used by filmmakers—that can rotate to point at anything in front of the aircraft. At 60,000 feet, the planes will be above as much of the atmosphere as possible to make observations of the corona. “Even if the plane makes turns or bumps you can still track the sun in the sky,” said Dr. Amir Caspi, principal scientist at Southwest Research Institute in Boulder, Colorado and in charge of the experiment.
Infrared Light
In one of the aircraft, images of the corona will be captured in seven different wavelengths by both a visible light camera and a new higher-resolution mid-infrared camera developed by NASA. That will help determine which structures in the middle and lower corona emit their light and which merely scatter light from the sun’s surface. At 60,000 feet, the planes will be flying at an altitude high enough to capture infrared light, which is absorbed by Earth’s atmosphere and is impossible to observe from ground level.
“It’s a range of infrared that you cannot see very well, if you’re on the ground—it’s also called mid-wave infrared and thermal infrared,” said Caspi. “You can’t see space-borne emission from the ground because the atmosphere will absorb it, and the atmosphere glows in exactly that wavelength range, so you have to be above as much of the atmosphere as you get to be able to make those observations.”
In the other WB-57 will be a spectrometer provided by the Solar Wind Sherpas, a group of solar researchers led by Shadia Habbal at the University of Hawaii who’s been imaging the totally eclipsed sun since 1995 from the ground.
Staying Mobile
Caspi’s experiment builds on a similar one on August 21, 2017, during the last total solar eclipse in the U.S.—the main difference being the new improved camera suite. “I didn’t actually get to see that eclipse because I was running the experiment at the WB-57 mission control center at Ellington Field, Houston,” said Caspi, who didn’t see his first total solar eclipse until April 20, 2023, in Western Australia.
“I’ll probably be somewhere in Texas where the best weather is likely to be because Southwest Research Institute is headquartered in Texas and because the WB-57s are based there,” said Caspi. However, Houston gets only 93% partial solar eclipse. “This time I’m hoping to have a mobile command center on the centerline of the path of totality,” said Caspi. “That way, we can run the experiment with the airplanes and then observe the eclipse right after.”
For the latest on all aspects of April 8’s total solar eclipse in North America, check my main feed for new articles each day.
Wishing you clear skies and wide eyes.
