National Geographic : 1992 May
helium, from helios, the Greek word for the sun; only later was it found on earth. Other eclipses showed over time that the corona changes shape in step with the 1 1-year sunspot cycle. But few eclipses attracted scientific observers like that of 1991. Many clustered on Mauna Kea. My experiments, tackling the mys- A RESEARCH tery of coronal heating, did not require elevation. My team set up two PROJECT tons of telescopes and electronics on the Big Island at Waikoloa. All SUPPORTED IN PART we needed was clear skies. AR BY YOUR On the evening before E day the thousands of tourists who had SOCI flocked to the Big Island thrilled to a fiery sunset, caused by globe girdling particles from the volcanic eruption of Mount Pinatubo in the Philippines. The particles rode stratospheric winds far above Mauna Kea; surely it would affect our viewing. Dawn broke on the 11 th with an unusually heavy cloud cover. On Mauna Kea, scientists worried about a rising fog. High cirrus clouds veiled the sky. The sun rose at 5:49 a.m. Forty-one minutes later the moon took its first bite of the sun, like some celestial Pac-Man. We glimpsed the vanishing sun through the clouds, and for a time it looked as if the sun would climb above them. Then, totality. But only after the clouds had won the race. The teams on the mountain fared better. There, the fog retreated, and the corona showed through the high clouds and volcanic haze. Most instruments worked well; only the haze and cirrus remained an unknown factor. Those observations and others will nourish solar astronomy for years. Among the experiments and early results: * The Canada-France-Hawaii (CFH) telescope, its room-size mirror the largest ever pointed at the sun, produced film and videotape that unexpectedly showed small regions in the corona changing brightness within seconds. Yet neither the CFH nor another large telescope on the mountain have found the predicted tiny explosions that could explain why the corona is so much hotter than the surface. * Electronic detectors able to make infrared images searched the inner solar system in vain for a ring of glowing dust reported two decades earlier. Despite the clouds and volcanic haze, the scientists say it should have shown up promi nently. Perhaps the ring had been temporary, deposited by a passing comet. * Other detectors were used to study prominences, magnetic fields, and the spectrum of the corona. The results reveal how the atmosphere of the sun varies in temperature and density. Total eclipses occur somewhere in the world every year or two. I plan to see one that will start over Uruguay and cross the South Atlantic Ocean this June 30. And when a particularly alluring eclipse crosses South America in 1994, I will gather up my students and my tons of equipment to try again to untangle some of the sun's mysteries-but not, I hope, harassed by clouds. *** THEIR FULL MEANING LOST FOR MILLENNIA, THE MEGALITHS OF STONEHENGE MARK THE MOVEMENTS OF THE SUN.