IfA Eclipse Expedition

The outer corona of the Sun is visible from Earth only during totality (lower left), when the Moon completely covers the disk of the Sun. Photos courtesy of the IfA Solar Expedition.

A group of IfA solar astronomers traveled to Libya to observe the March 29 total solar eclipse. There, from a camp deep in the blistering Libyan Sahara desert along the centerline of the eclipse path, they carried out an ambitious program of spectroscopic and imaging experiments to learn more about the outer regions of the Sun, the solar corona.

The team took a thousand pounds of scientific equipment, including three new instruments specially designed to study the outer corona, which extends to several solar radii above the surface. The outer corona is visible from Earth only during a total solar eclipse, when the brightness of the sky dims significantly. Because totality would last only four minutes and six seconds, each team member chose a specific assignment that would optimize his or her contribution to the experiment.

The eclipse expedition: C-130 transport plane and inside the cargo area. Helicopter transport to campsite. Observing tents and equipment set up.

The team was attempting to answer several key questions: How much interplanetary dust exists in the corona, and what is its size and composition? Can the interstellar gas enter the heliosphere (the region in space influenced by the Sun) and make its way into the corona? How does the solar magnetic field escape from the Sun?

A total eclipse enables scientists to measure the coronal spectrum in the visible and near-infrared wavelengths. Polarized images of the corona's spectrum can indicate the direction of the solar magnetic field, and the temperature distribution of various atoms, molecules, and ions in the corona. Anything that is not of solar origin, such as interplanetary dust or neutral atoms from the interstellar medium, produces a spectrum and polarized image different from that of the Sun.

The success of the observations will open the door for refined measurements of the corona's elusive magnetic field and its ionic and dust composition using large telescopes like the Advanced Technology Solar Telescope, which may be built on Haleakala on Maui. 

Astronomer Shadia Habbal, the organizer of the expedition, stated, "We received enormous assistance from the people of Libya, and could not have succeeded without their support." Astronomer Jeff Kuhn added, "Despite the daunting complexity of running a series of infrared and visible instruments from the middle of the Sahara, in the final analysis, it was the right choice—the weather and observing conditions were superb."

In addition to Shadia Habbal and Jeff Kuhn, the group from the IfA also included astronomers Donald Mickey and Ilia Roussev, postdoctoral fellow Huw Morgan, and graduate student Sarah Jaeggli. They were joined by Judd Johnson (an engineer from Colorado), Adrian Daw (Appalachian State University in North Carolina), and Martina Arndt (Bridgewater State College in Massachusetts).