UH astronomers observe eclipse in Libyan desert

The team reports preliminary evidence of an interstellar wind blowing past the sun

Six University of Hawaii astronomers traveled to the Sahara desert in Libya with a ton of special instruments to study the sun's outer corona for four minutes and six seconds during a total eclipse on March 29.

"Each one of those seconds was precious," said Jeff Kuhn, associate director of the UH Institute for Astronomy's Maui Division.

The team took three new instruments developed at the IFA, some specialized imaging cameras and an infrared spectrograph to look at the sun's outer corona, which is only visible during a total solar eclipse.

"It was a logistical nightmare and it's not over yet," Kuhn added. "We don't have the equipment (back) yet from Libya."

The instruments were mostly to look at infrared wavelengths, but one sensitive instrument looked at the sun in visible light, Kuhn said. "We had lots of adventure with the equipment, but in the end everything worked superbly.

"What we were after was to try to understand something about the cool part of the hot corona, which is normally millions of degrees," he said. "It's that part of the sun we can't see."

He said the Hawaii team was looking for evidence that there is a breeze or interstellar wind blowing through the solar system. "We were looking to find that wind as it passed by the sun."

The astronomers are only starting to analyze their voluminous data, but they did see evidence of the wind, Kuhn said.

Instead of a temperature of millions of degrees, the outer regions of the sun have cooler gas that is only a few thousands of degrees, he said.

"It means there is a wind blowing through the solar system through interstellar space. It impinges on the earth and also impinges on the sun."

It can only be seen when the bright part of the sun is blocked out during an eclipse, he said.

Also, for the first time, Kuhn said the astronomers got a big piece of the infrared spectrum of the corona, which paves the way for the Advanced Technology Solar Telescope being planned for Haleakala, Maui.

When the ATST "comes on line, we will know how to use it," he said. The world's largest solar optical observatory will have a 13-foot primary mirror for detailed views of the sun and its corona.

An environmental appraisal is under way and hopefully will be completed within six months, Kuhn said.

Others on the UH eclipse team were astronomers Shadia Habbal, Don Mickey and Ilia Roussev, postdoctoral fellow Huw Morgan and graduate student Sarah Jaeggli.

Habbal, who organized the expedition, said, "That we managed to get to the eclipse site was a miracle and an incredible feat on the part of Libya," and observing conditions "were terrific."

Also, all the experiments worked, she said, "even though a few days before, we had one calamity after another."

Habbal said Libya advertised for scientists to view the eclipse from the Sahara and gave them "enormous assistance," including organizing a conference two days before the event. "No other country did that."

At least 200 people had gathered at the observing site in the southern half of Libya in the middle of the desert, she said.

The astronomers and others were flown there by military plane and military helicopters, and Libya provided them with food, water and shelter, she said. "It was a remarkable feat on their side. We paid for it but they provided it."