An annular

solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an eclipse season, approximately every six mo ...

occurred on September 23, 1987. A

occurs when the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...

passes between

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surf ...

and the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared rad ...

, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's

apparent diameter The angular diameter, angular size, apparent diameter, or apparent size is an angular distance describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the visual angle, and in optics, it is ...

is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an

annulus Annulus (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to: Human anatomy * ''Anulus fibrosus disci intervertebralis'', spinal structure * Annulus of Zinn, a.k.a. annular tendon or ''anulus tendineus co ...

(ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Annularity was visible in the

Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...

(today's

Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Eastern Europe. It borders Russia Russia (, , ), or the Russian Federation, is a transcontinental coun ...

), China (including

Shanghai Shanghai (; , , Standard Mandarin pronunciation: ) is one of the four direct-administered municipalities of the People's Republic of China (PRC). The city is located on the southern estuary of the Yangtze River, with the Huangpu River flowin ...

), southwestern

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 millio ...

Okinawa Islands The Okinawa Islands ( or ) are an island group in Okinawa Prefecture, Japan and are the principal island group of the prefecture. The Okinawa Islands are part of the larger Ryukyu Islands group and are located between the Amami Islands of Kago ...

of Japan except

Kume Island is an island, part of the Okinawa Islands and administratively part of the town of Kumejima, Okinawa Prefecture is a prefecture of Japan. Okinawa Prefecture is the southernmost and westernmost prefecture of Japan, has a population of 1,45 ...

and the southwestern tip of

Kerama Islands The are a subtropical island group southwest of Okinawa Island in Japan. Geography Four islands are inhabited: Tokashiki Island, Zamami Island, Aka Island, and Geruma Island. The islands are administered as Tokashiki Village and Zamami V ...

, the Federal States of Micronesia,

Papua New Guinea Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...

Solomon Islands Solomon Islands is an island country consisting of six major islands and over 900 smaller islands in Oceania, to the east of Papua New Guinea and north-west of Vanuatu. It has a land area of , and a population of approx. 700,000. Its ca ...

, Rotuma Islands of Fiji,

Wallis Islands Wallis and Futuna, officially the Territory of the Wallis and Futuna Islands (; french: Wallis-et-Futuna or ', Fakauvea and Fakafutuna: '), is a French island collectivity in the South Pacific, situated between Tuvalu to the northwest, Fiji ...

and West Samoa (the name changed to Samoa later). Occurring only 5 days after apogee (Apogee on September 18, 1987), the Moon's apparent diameter was relatively small.

Observation

Five radio observation stations were present in China at the time of the eclipse, two of which were within the annularity, in

Ürümqi Ürümqi ( ; also spelled Ürümchi or without Umlaut (diacritic), umlauts), formerly known as Dihua (also spelled Tihwa), is the capital of the Xinjiang, Xinjiang Uyghur Autonomous Region in the far Northwest China, northwest of the Peopl ...

and

respectively. A partial solar eclipse was observed from the other three, including one in

Nanjing Nanjing (; , Mandarin pronunciation: ), Postal Map Romanization, alternately romanized as Nanking, is the capital of Jiangsu Provinces of China, province of the China, People's Republic of China. It is a sub-provincial city, a megacity, and t ...

where the eclipse was close to annularity, and the rest two in

Beijing } Beijing ( ; ; ), alternatively romanized as Peking ( ), is the capital of the People's Republic of China. It is the center of power and development of the country. Beijing is the world's most populous national capital city, with over 21 ...

and

Kunming Kunming (; ), also known as Yunnan-Fu, is the capital and largest city of Yunnan province, China. It is the political, economic, communications and cultural centre of the province as well as the seat of the provincial government. The headqua ...

. The Department of Mathematics and Physics of the

Chinese Academy of Sciences The Chinese Academy of Sciences (CAS); ), known by Academia Sinica in English until the 1980s, is the national academy of the People's Republic of China for natural sciences. It has historical origins in the Academia Sinica during the Repub ...

and the Chinese Astronomical Society held a meeting in Kunming in December 1986, deciding that on-site observation would be conducted at each station, among which the Shanghai Astronomical Observatory was considered to have the best location with a larger magnitude of the eclipse, longer duration and larger

solar zenith angle The solar zenith angle is the zenith angle of the sun, i.e., the angle between the sun’s rays and the vertical direction. It is the complement to the solar altitude or solar elevation, which is the altitude angle or elevation angle between th ...

. The Shanghai Astronomical Observatory conducted observations with seven different wave bands using a 25-metre radio telescope. The

Yunnan Astronomical Observatory Yunnan Astronomical Observatory (YAO; ) an institution of Chinese Academy of Sciences sits on the Phoenix Hill in the east suburbs of Kunming, Yunnan, China China, officially the People's Republic of China (PRC), is a country in East Asi ...

located in Kunming also conducted a multi-band joint observation of the partial solar eclipse. The Chinese Research Institute of Radio Wave Propagation conducted observations with a high-frequency skywave radar located in

Xinxiang Xinxiang ( ; postal: Sinsiang) is a prefecture-level city in northern Henan province, China. It borders the provincial capital of Zhengzhou to its southwest, Kaifeng to its southeast, Hebi and Anyang to its north, Jiaozuo to its west, and the ...

on the southern limit of annularity. Uneven structure and motion were observed in the ionosphere, the highest operating frequency was found changed during the eclipse, and large-scale fluctuations continued after the eclipse.

Related eclipses

Eclipses of 1987

* A hybrid solar eclipse on March 29. * A penumbral lunar eclipse on April 14. * An annular solar eclipse on September 23. * A penumbral lunar eclipse on October 7.

Solar eclipses of 1986–1989

Saros 134

Metonic series

Notes

References

1987 9 23 1987 in science 1987 9 23 September 1987 events {{Solar-eclipse-stub