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).