Eclipse Experiment Over in Five Minutes

— -- Thursday evening, after the sky had gone dark a second time, Jeff Kuhn had a simple verdict on how the day had gone.

“It was good,” he said.

Ten days had passed since the Michigan State University physicist and eight other researchers had landed in Panama aboard a specially modified C-130 transport aircraft containing their one-of-a-kind eclipse-watching instruments. Over the past week, they flew three rehearsal flights, each lasting five or six hours, to work out kinks. They worried about thunderstorms. They worried about getting permission to fly into Colombian air space if that’s where the clear spots turned out to be.

A Closer Look at the Sun

Kuhn’s project sought to capture never-seen-before light from the sun’s atmosphere—light that may cast insight on the web of magnetic fields that lie out there.

And, as Thursday’s solar eclipse swept over them, the quarter-million-dollar experiment worked. A quick, preliminary perusal of the data indicated their instruments had indeed captured the infrared light they sought.

“There is some tentative evidence we do see this emission,” Kuhn said, “but I’m not ready to write that down in the press. I would just say it’s very promising.”

The day had begun much earlier. They arrived at Howard Air Force Base at 8, and scoured the weather reports for an hour, looking for clear skies. The spotty weather forced them to move their rendezvous point with the eclipse a couple hundred miles to the south. But that’s the advantage of a flying eclipse laboratory. (Kuhn’s two previous ground-based eclipse experiments had been largely thwarted by cloud cover.)

At 10 a.m., they took off.

No More Rehearsals

“Eclipses are very frustrating things,” Kuhn had said a couple of days earlier. “There are also second thoughts about whether it’s worth the effort.”

Eclipses are the Olympics of scientific research, a fleeting opportunity to explore the sun’s corona—the ghostly halo of light visible only during a total eclipse. The researchers from Michigan State, the Max Planck Institute in Germany, the National Solar Observatory and the National Center for Atmospheric Research had prepared for months. Now, rehearsals were over. This flight was the performance, those few minutes when the sun disappeared behind the moon.

In particular, Kuhn and his collaborators hoped to spot a specific color of infrared light emitted by silicon ions whose outer eight electrons have been ripped away by the intense heat of the sun’s corona. Eventually, by analyzing how the magnetic fields of the corona splits this color into two slightly different shades, the scientists may better understand how the fields heat the corona to several million degrees—far hotter than the 11,000 degrees Fahrenheit at the sun's surface—and accelerate the particles of solar wind that blow out of the sun.

The goal of this trip was just to see these never-seen-before photons. The infrared camera, based on heat-seeking missile technology, also promised to capture the best infrared images to date of the corona. It was possible they might detect rings of dust orbiting around the sun, much like Jupiter’s rings.

Darkness Falls

At 12:28 p.m., the 1,200-mile-per-hour eclipse shadow overtook the plane. Flying at 250 mph in the same direction as the shadow, totality was stretched to five minutes, more than a minute longer than what people saw on the ground.

The people in the back of the plane didn’t see it at all, except on a video monitor.

The five minutes passed, and the sun began to emerge from behind the moon. They flew around for another two hours, collecting more data to calibrate their readings.

Then Kuhn opened a bottle of scotch.

Back on the ground, there was a press conference, then the ride back to Panama City and a celebratory dinner.

“I hesitate to think what we would have done if it had been a disappointment,” Kuhn said that evening. “I have to say, I had it 50-50 odds in the end. It’s a relief.”

Analyzing the data in detail will take months. Kuhn talked, hesitatingly, of flying the experiment again when the next solar eclipse sweeps across Europe in 1999. He hopes successful discoveries out of this experiment might prod the building of a large infrared coronagraph—a telescope that can make its own eclipse and enable corona observations at any time.

Dreams like that are years and millions of dollars away.