Solar eclipse will be longest for more than a century

日期:2019-03-08 03:07:21 作者:达留郎 阅读:

By Fred Espenak and Jay Anderson, (Image: Alphonse Sterling/NASA/Samaiya Farid/Antoniya Savcheva/SAO) Watch the eclipse online – Astro-Native Technologies/Eclipse City and Live! Eclipse 2009 are among the websites that plan to offer streaming video on eclipse day. See also: July eclipse is best chance to look for gravity anomaly For the second time in a year, a total eclipse of the sun is about to cross China. But unlike the moon’s hard-to-reach shadow path last August, the celestial spectacle on Wednesday will darken major cities, densely populated countryside, and a vast expanse of tropical ocean. And the eclipse itself will be a monster, with totality – when the sun is completely covered by the moon – lasting more than 6.6 minutes at maximum. That makes this the longest totality until 2132. A total solar eclipse occurs once every year or two on average, but each is visible only from a narrow track covering less than 1 per cent of Earth’s surface. The eclipse of 1 August 2008, was visible only from parts of the Arctic, Siberia, and central Asia. Nevertheless, thousands of enthusiasts travelled by land, air, and polar icebreaker for the chance to bask briefly in the silvery twilight glow of the sun’s corona. The main reason why this year’s totality lasts so long is because the eclipse starts just a few hours after the moon reaches perigee, the point at which it is closest to Earth in its orbit. At such a close distance, the moon appears fully 8 per cent larger than the sun and casts a broader than usual shadow. At the point of greatest eclipse in the western Pacific, the path of totality is 258 km wide. The umbra (dark central portion) of the lunar shadow first touches Earth at sunrise at 0053 GMT in the Gulf of Khambhat off western India. The shadow takes just 8 minutes to cross India before spilling into northern Bangladesh and easternmost Nepal. A minute later, the umbra engulfs most of Bhutan, while the eclipse duration on the central line crosses the 4-minute mark. The sun’s altitude is 21°. The shadow then crosses northern Burma, a corner of Tibet, and China’s Yunnan province. Passing through the middle of Sichuan province, the eclipse track darkens the capital city of Chengdu (2 million inhabitants, 3.3 minutes of totality), Chongqing (4.1 million, 4 minutes), and Wuhan (9.7 million, 5.5 minutes). Travelling nearly due east, the shadow track encompasses the meandering course of the Yangtze River. Near the Pacific coast, Hangzhou’s 4 million citizens experience a total eclipse lasting 5.3 minutes. The sun’s altitude is now 55°. A minute later Shanghai, China’s largest city with 20 million people, plunges into totality for 5 minutes, though it is well north of the central line. This may be the most people that have ever been in the moon’s shadow at once. As it moves out over the East China Sea, the umbra sweeps over Japan’s Ryukyu Islands, then Iwo Jima and Kitaio Jima, before curving southeast across the Pacific. The instant of greatest eclipse occurs at 02:35:19 GMT, when totality lasts longest: 6 minutes 39 seconds. This happens over open ocean with no land in sight. The second half of the eclipse path crosses nothing but ocean and a few tiny islands and coral atolls among the Marshall Islands and Kiribati. The total eclipse finally ends at 0418 GMT, at sunset about 1000 km northwest of Tahiti. The moon’s shadow lifts off Earth and returns to space, after covering 0.7 per cent of Earth’s surface in 3.4 hours. On 11 July 2010, this part of the world will be favoured with its third total solar eclipse in as many years. The track is almost entirely over the South Pacific. Easter Island and southern Chile (at sunset) offer the only landfalls. And the South Pacific also hosts the next one, on 13 November 2012. A total solar eclipse won’t cross the Americas until 21 August 2017, when the moon’s umbra will sweep from Oregon to South Carolina. Courtesy of Sky and Telescope magazine Fred Espenak, an astronomer at NASA’s Goddard Space Flight Center, runs NASA’s eclipse website and his own. He is the co-author of Totality: Eclipses of the Sun. Meteorologist Jay Anderson (University of Manitoba) has created eclipse weather forecasts since 1979 and has journeyed worldwide to check his predictions in person. More on these topics: