A Centennial Astronomical Feast: The July 22 Total Solar Eclipse along the Yangtze
Steed posted on 2009-07-05 16:20On July 22, the moon’s huge shadow will once again sweep across our country, and the spectacle of a total solar eclipse will once more pay a visit to China. Although it has been less than a year since the last total solar eclipse, these two eclipses could hardly be more different.
The total solar eclipse of August 1, 2008, occurred in the evening, when the sun was already slanting low in the western sky at totality, and the duration was only a little over two minutes. This eclipse, by contrast, will occur after 9 a.m., when the sun is already high in the eastern sky and not easily obscured by buildings or by low-lying haze. Most important of all, the totality will last as long as 6 minutes 39 seconds at most (5 minutes 55 seconds at most within China).
The reason it lasts so long is mainly that only a few hours before the eclipse, the moon will have just passed perigee, while the sun will happen to be near apogee. Thus the moon, which usually appears about the same size as the sun, will now look 8% larger than the sun, and the shadow it casts on the earth will be correspondingly much wider than usual. In fact, this total solar eclipse will be the longest one in the next123 years, truly “the last of its kind”—at least those who are alive now will not live to see a longer total solar eclipse.
From another perspective, this eclipse can also be called “unprecedented.” When a total solar eclipse occurs, only within the narrow, elongated belt directly swept by the moon’s shadow—that is, the path of totality—can one see the moon completely block the sun. The previous path of totality crossed the sparsely populated, inconvenient-to-reach northwest (see the article “Go See the Total Solar Eclipse on August 1” in the July 2008 issue of Global Science), and although many “eclipse chasers” traveled great distances to the path of totality (see the article “Direct Hit: The Total Solar Eclipse” in the September 2008 issue of Global Science), the number lucky enough to witness it with their own eyes was still small in the end.
This year’s total solar eclipse on July 22 breaks with the usual rule that the path of totality “avoids the crowds”: the moon’s shadow will sweep across the densely populated middle and lower reaches of the Yangtze River, passing through Tibet, Yunnan, Sichuan, Chongqing, Hubei, Hunan, Jiangxi, Anhui, Jiangsu, Zhejiang, Shanghai and other provinces and municipalities, among which six provincial capital-level cities—Chengdu, Chongqing, Wuhan, Hefei, Hangzhou, and Shanghai—will in turn be plunged into darkness, and the number of other towns and cities shrouded by the moon’s shadow is even too many to count. This total solar eclipse will be the one covering the largest population in history; the number of people within the path of totality is estimated at 300 million—in other words, on average, one out of every four Chinese people will be able to witness the total solar eclipse right at their doorstep without having to travel far, and the other three will also have the chance to see partial solar eclipses of varying degrees. This will be the most abundant, most generous, and most down-to-earth astronomical feast of the 2009 International Year of Astronomy.
There is yet another reason why the approaching eclipse seems especially precious. After this total solar eclipse is over, the moon’s shadow will again move away from our country, and there will be no total solar eclipses anywhere within China for the next 25 years. If you miss this “unprecedented and unrepeatable” total solar eclipse, then unless you go abroad to follow the moon’s shadow, you will have to wait until March 20, 2034, in the barren uninhabited zone of the Qinghai-Tibet Plateau, in the western low sky at dusk, to welcome a total solar eclipse lasting less than two minutes.
Therefore, this total solar eclipse taking place in the middle and lower reaches of the Yangtze on July 22 is absolutely not to be missed.
Where can the path of totality be seen?
The moon’s shadow will enter China from the Tibet–Yunnan border region, cross our country from west to east through the middle and lower reaches of the Yangtze River, and finally leave the coastline at the border between Shanghai and Zhejiang to move into the Pacific Ocean. The region swept by the shadow is called the path of totality. It is about 250 kilometers wide and extends roughly 2,400 kilometers within China. The 300 million people in the path of totality will have the chance to see the total solar eclipse; other regions will be able to see partial solar eclipses of varying degrees.
Chengdu, Sichuan Province
Chengdu is the first major city the total solar eclipse passes after entering China, and is located about 90 kilometers north of the central line of the path of totality. Here, the eclipse will begin at 8:07 a.m. and end at 10:26 a.m. The most splendid phase of totality will begin at 9:11:11 a.m. and last 3 minutes 13 seconds. Cities in Sichuan Province such as Kangding, Ya’an, Leshan, Meishan, Ziyang, Zigong, Neijiang, Suining, Nanchong, Guang’an, and Dazhou will also be able to see the total solar eclipse. The Emei Mountain Scenic Area will likewise welcome the eclipse, with totality lasting 4 minutes 43 seconds from 9:09:06 a.m. Because Emei Mountain is at a relatively high elevation, if the weather is clear, it will be an excellent place to observe the total solar eclipse.
Chongqing Municipality
Chongqing will be the first municipality directly under the central government swept by the moon’s shadow. The sun will be completely swallowed by the moon at 9:13:14 a.m., for 4 minutes 06 seconds. At the time of totality, the sun will appear about 40 degrees above the eastern horizon, and it will not be easy for the uneven terrain of this mountain city to block it. On the central line of the path of totality about 70 kilometers north of Chongqing, the duration of totality has already reached 5 minutes. Although the average cloud cover here in July is 52%, slightly better than in Chengdu, in Chongqing, known as the “Fog City,” the lingering haze may have a considerable effect on the eclipse.
Wuhan, Hubei Province
Wuhan is the major city closest to the central line of the path of totality, and Wuhan Tianhe Airport even lies exactly on the central line. The initial contact will occur at 8:14:55 a.m., and the eclipse will fully end at 10:46:19 a.m. The totality phase will last from 9:24:01 a.m. to 9:29:25 a.m., a total of 5 minutes 24 seconds. Cities along the Yangtze River in Hubei Province—such as Enshi, Yichang, Jiangling, Shashi, Jingmen, Suizhou, Xiaogan, Xianning, Huanggang, Ezhou, and Huangshi—will all be able to see the total solar eclipse. The Yangtze River Three Gorges will also be shrouded by the moon’s shadow, but with the steep mountains on both banks, a cruise ship on the Three Gorges may not be a good place to watch the eclipse.
Hefei, Anhui Province
Hefei is the provincial capital city closest to the edge of the path of totality in this eclipse. The totality phase will begin at 9:30:55 a.m., but the duration will be only 1 minute 49 seconds. Areas south of Hefei within Anhui Province will all be able to see the total solar eclipse; in cities such as Anqing, Guichi, Tongling, and Xuancheng, totality will last more than 5 minutes 20 seconds. The total solar eclipse will also appear over the famous Huangshan Scenic Area, competing in splendor with the strange pines, grotesque rocks, and sea of clouds, for a duration of 4 minutes 39 seconds.
Hangzhou, Zhejiang Province
Hangzhou is located 50 kilometers south of the central line of the path of totality. The beautiful West Lake will迎来 a total solar eclipse at 9:34:12 a.m., lasting 5 minutes 20 seconds, though the mist by the lake may affect the transparency of the sky. Cities in Zhejiang Province such as Huzhou, Jiaxing, Shaoxing, Ningbo, and Zhoushan will all be able to see the total solar eclipse; among them, Jiaxing is closest to the central line of the path of totality, and there the phase of totality will last 5 minutes 52 seconds, the longest totality duration in China’s urban areas. In addition, places in Jiangsu Province such as Changzhou, Wuxi, and Suzhou will also be able to see the total solar eclipse.
Shanghai Municipality
Shanghai, with a population of nearly 20 million, will be the final stop of this total solar eclipse within China, and may set the record for the largest number of people simultaneously shrouded by the moon’s shadow in history. The center of Shanghai is about 70 kilometers before the central line, and the total solar eclipse will begin at 9:36:48 a.m. and last about 5 minutes. The farther south one goes, the longer the duration of totality; Yangshan Port, located right on the central line, can see the longest total solar eclipse within China, lasting as long as 5 minutes 57 seconds. If no typhoon strikes then, Shanghai will be one of the best places in China to observe the total solar eclipse.
Note: Even within the same city, the exact time and duration of the total solar eclipse will not be exactly the same at different locations. To check the detailed eclipse times for your area, please visit the online interactive map: http://xjubier.free.fr/en/site_pages/solar_eclipses/TSE_2009_GoogleMapFull.html.
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strong>What should one look for in a solar eclipse?
A complete solar eclipse lasts more than 2 hours; outside the brief phase of totality, only part of the sun is covered by the moon. Even so, the part of the sun not covered still shines brilliantly, so under no circumstances should you look directly at the sun without protection! Wearing certified solar-viewing glasses, or using fully blackened black-and-white film, you can observe the sun directly with the naked eye. Light spots cast through gaps in leaves or through a small hole can also show you the eclipse image. If you have a telescope, the safest method is to project the sun’s image onto a white board or white paper. Unless a professional filter or filter film is installed in front of the telescope objective, never observe the sun directly through a telescope.
As the phase of totality draws near, the sky will clearly darken, and the sunlight will also begin to dim. If you observe the changes in the sky in an open area, you will notice the moon’s shadow sweeping in from the western low sky, and then quickly disappearing over the eastern horizon after totality ends. Venus and Mercury, these two bright planets, will even flash into view on the upper and lower sides of the sun before the moon has completely covered it. At that moment, your eyes are the best observing instrument. Changes in temperature and the unusual behavior of small animals are also worth paying attention to.
The instant when the moon completely covers the sun is called second contact, and the instant when the sun reappears is called third contact. The briefest yet most beautiful Bailey’s beads and diamond ring in a total solar eclipse will appear at these two key moments. They are formed by the last ray of sunlight at second contact, or the first ray of sunlight at third contact, shining through the moon’s uneven edge. At this point you can set aside all filtering equipment and stare directly through the telescope at the black sun. Do not blink, because Bailey’s beads and the diamond ring are both fleeting marvels.
During totality, the sunlight will disappear completely. If observed directly through a telescope, you can see a red rim appear along the edge of the black sun; that is the sun’s chromosphere. Flame-tongued prominences should also extend outward from the edge of the black sun, where solar storms begin. Wrapping around them is the silvery-white corona, where you can see clear featherlike textures extending outward, with an effect surpassing any photograph you have seen before. However, do not spend all of the brief totality staring through the telescope. Lift your head and take a look at the “night sky”; you will find the magnificent winter constellations in the southern sky to the right of the black sun.
To personally feel the震撼 brought by this astronomical wonder is an experience that no photograph or video can replace.
For a firsthand account of the total solar eclipse of August 1, 2008, see below:
Direct Hit: The Total Solar Eclipse
Tags: Solar Eclipse, Global Science
Author Introduction
Steed
Editor of the “chief seat” at “Global Science”!Translated from the Chinese original with AI assistance. The original text is authoritative.
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