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A Solar Eclipse on Enewetak

by Beverly Lynn-Wilson

IfA Eclispe Team 2009
Team members posed in front of the main observing tent. Standing: Judd Johnson, Shadia Habbal, Adalbert Ding, Martina Arndt, Mindy Lekberg, and Joni Lang. Seated: Huw Morgan, Isabelle Scholl, Emily Mount, Beverly Lynn-Wilson, Dave Harrington, and Sarah Jaeggli.

The diamond ring flashed. In an instant, the Moon covered the Sun and extinguished the light. I nearly shouted when I realized I was seeing my first total solar eclipse, after two attempts that failed due to bad weather. But I remained quiet because the IfA Eclipse Team I accompanied to Enewetak in the Marshall Islands needed to concentrate on gathering data. The team was led by IfA astronomer Shadia Habbal.

After waiting for an imperceptibly slow-moving Moon to eat away the Sun, darkness came so quickly that my brain barely had time to register what I had seen: tiny blips of light called Bailey's Beads forming a narrow band encircling the Sun, and then a last handful of sunlight glowing like a diamond.

Darkness descended on July 22 at 3:28 p.m. For five minutes and 40 seconds, it wasn't daytime, but neither did it look entirely like night. A yellow-white Venus shimmered low in the western sky, and a few stars appeared, but the sky was not the right shade of blue for twilight. This sky had more royal mixed in with the indigo, making it brighter. Under the blue, along the western horizon, the sky was an orangey-yellow. The ocean I was looking over, on the other hand, changed from royal blue to the usual twilight indigo, as if somehow the world had turned upside down.

In contrast to the soft colors and sharp shadows around me, the Sun looked starkly black with the silvery white lion's mane of the corona now visible. The Sun is so bright that you can see its atmosphere (corona) only during a total eclipse.

Totality is the best time for scientists to study the corona, especially in regions close to the Sun. We know remarkably little about this nuclear reactor that makes life possible on Earth. Particles streaming out from the Sun can disrupt communications and GPS devices here on Earth, cause power surges, and put astronauts at risk. The more we learn, the more we can ameliorate these disruptions and risks.

During this eclipse, the scientists collected data about ions of iron and helium. They took spectra to obtain infrared data. Technology has only recently become advanced enough to study the corona in the infrared, so we have very little data so far in that area.

The data collection involved months of planning, weeks of instrument calibration, and several practice sessions. Everything had to proceed flawlessly on eclipse day, since scientists had only minutes and no second chances. The data will take weeks or months to analyze. Added to data from previous and future eclipses, scientists are slowly filling in missing pieces of the puzzle that is the corona.

As suddenly as totality began, a tiny globule of Sun reappeared, as if someone had flipped on a switch, and the light returned. The globule grew to a thin crescent and then a fat crescent, looking like phases of the Moon. In an hour and 20 minutes the entire Sun was back.

For a more complete description of the trip and photographs, see http://iyahawaii.blogspot.com/2009/08/eclipse-trip.html.

Beverly Lynn-Wilson is an active member of the Friends of the IfA.