Great eclipse of 2009

The longest total solar eclipse of the 21st century begins at dawn near the west coast of India and crosses southern China before heading out into the Pacific Ocean. Red lines denote regions where a partial eclipse is visible. Blue lines indicate mideclipse in Universal Time. Click on the image for a larger version.

Fred Espenak

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 July 22, 2009, will darken major cities, densely populated countryside, and a vast expanse of tropical ocean. And the eclipse itself will be a monster, with totality 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% of Earth’s surface. The eclipse of August 1, 2008, was visible only from parts of the Arctic, Siberia, and central Asia. Nevertheless, thousands of enthusiasts traveled 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. At such a close distance, the Moon appears fully 8% 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 (161 miles) wide.

The umbra (dark central portion) of the lunar shadow first touches Earth at sunrise at 00:53 Universal Time 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°.

Eclipse map for eastern China

On July 22, 2009, the Moon's shadow passes over several large cities in Cina — including Shanghai. Red labels indicate the duration of totality, the Sun's altitude in the sky, and the Universal Time of mideclipse.

Fred Espenak

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). Traveling 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 2:35:19 UT, 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 4:18 UT, at sunset about 1,000 km northwest of Tahiti. The Moon’s shadow lifts off Earth and returns to space, after covering 0.7% of Earth’s surface in 3.4 hours.

Weather Prospects

Monsoon climates and tropical breezes do not bode well for this eclipse in India and China. Along the entire track the season is humid, with frequent clouds and rain. But in some spots the statistics tilt just barely to the good side of 50-50.

Cloud cover for the 2009 total solar eclipse

Prospects for clear skies along the eclipse path are chancy. Data are derived from NOAA's International Satellite Cloud Climatology Project. Click on the graph for a larger view showing the entire centerline.

S&T: Casey Reed (source: NOAA)

The dullest skies are on the slopes of the Himalayas, where, at Guwahati for instance, the chance of clouds exceeds 85%. Prospects improve in China: around 55% average cloud cover in July. Shanghai shows an average of 54% sunny.

Pollution in China will be a factor to consider for those who want to view or photograph the outer fringes of the corona. On sunny days the endemic brown haze is much less visible than in poorer weather; blue sky shines through. If skies are clear, or nearly so, even Shanghai’s pollution is unlikely to affect the spectacle. Wuhan offers cleaner skies at the expense of a few percentage points in the cloudiness odds and seconds in eclipse duration.

Cloud cover along the track reaches its minimum near Iwo Jima. Ships may be able to find a hole in the clouds, because most weather systems are relatively small and can be dodged with a little planning.

But not typhoons. July is the middle of typhoon season, and the likelihood of one in the eclipse track between Japan and the Philippines is probably close to 10%.

Future Total Eclipses

On July 11, 2010, this part of the world will be favored 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 November 13, 2012.

A total solar eclipse won’t cross the Americas until August 21, 2017, when the Moon’s umbra will sweep from Oregon to South Carolina.

Astronomer Fred Espenak (NASA/Goddard Space Flight Center) runs NASA's eclipse website and his own. He coauthored (with Mark Littmann and the late Ken Willcox) the newly published 3rd edition 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.


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