20th-century annular solar eclipse
An annular solar eclipse occurred at the Moon's ascending node of orbit on Wednesday, December 14, 1955, with a magnitude of 0.9176. A solar eclipse occurs when the Moon passes between Earth and the Sun, 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 is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Occurring about 1 day before apogee (on December 15, 1955, at 7:10 UTC), the Moon's apparent diameter was smaller.
The duration of annularity at maximum eclipse (closest to but slightly shorter than the longest duration) was 12 minutes, 9.17 seconds in the Indian Ocean. It was the longest annular solar eclipse from December 17, 168 to January 14, 3080. Among all the 23740 solar eclipses from 4000 BC to 6000 AD, 7881 are annular, and only 3 of them are longer than this one. This was the 20th member of Solar Saros 141, and the last of first set of solar eclipses without a penumbral internal contact (without a penumbra northern limit), the next event is the December 24, 1973 event, which is the first of 19 solar eclipses with a penumbral internal contact (has penumbral northern and southern limits) until 2298 Jul 09.
Annularity was visible from French Equatorial Africa (the part now belonging to Chad), Libya, Anglo-Egyptian Sudan (the part now belonging to Sudan) including the capital city Khartoum, French Somaliland (today's Djibouti) including the capital Djibouti City, British Somaliland (today's Somaliland) including the capital city Hargeisa, the Trust Territory of Somaliland (today's Somalia), the Maldives, Andaman and Nicobar Islands, Burma, Thailand including the capital city Bangkok, Cambodia, Laos, North Vietnam and South Vietnam (now belonging to Vietnam), China, British Hong Kong, Taiwan, and Ryukyu Islands. A partial eclipse was visible for parts of East Africa and Asia.
This was the third of four central solar eclipses visible from Bangkok from 1948 to 1958, where it is extremely rare for a large city to witness four central solar eclipses within 10 years.
Extreme duration.
With a maximum length of annularity duration of 12 minutes and 9.17 seconds, this is the longest solar eclipse in the millennium, as well as the longest duration in Saros 141 and one of the longest eclipses ever observed. The annular path begins in northern Africa, then passing Maldives (near the maximum eclipse), then crosses just southern edge of Sri Lanka, then the track continues to some countries in Indochina and the track ends just slightly after the track passes Taiwan.
Observation.
A joint team of the Georgetown University Astronomical Observatory, Washington, D.C. and the United States Air Force observed the annular eclipse in multiple locations around the world. Among them, in Khartoum, capital of Anglo-Egyptian Sudan, the partial phase started before sunrise, and the annular phase was shortly after sunrise. The team measured the refraction with the zenith distance between 80° and 90°.
Eclipse details.
Shown below are two tables displaying details about this particular solar eclipse. The first table outlines times at which the moon's penumbra or umbra attains the specific parameter, and the second table describes various other parameters pertaining to this eclipse.
Eclipse season.
This eclipse is part of an eclipse season, a period, roughly every six months, when eclipses occur. Only two (or occasionally three) eclipse seasons occur each year, and each season lasts about 35 days and repeats just short of six months (173 days) later; thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. In the sequence below, each eclipse is separated by a fortnight.
Related eclipses.
Solar eclipses of 1953–1956.
This eclipse is a member of a semester series. An eclipse in a semester series of solar eclipses repeats approximately every 177 days and 4 hours (a semester) at alternating nodes of the Moon's orbit.
The partial solar eclipses on February 14, 1953 and August 9, 1953 occur in the previous lunar year eclipse set.
Saros 141.
This eclipse is a part of Saros series 141, repeating every 18 years, 11 days, and containing 70 events. The series started with a partial solar eclipse on May 19, 1613. It contains annular eclipses from August 4, 1739 through October 14, 2640. There are no hybrid or total eclipses in this set. The series ends at member 70 as a partial eclipse on June 13, 2857. Its eclipses are tabulated in three columns; every third eclipse in the same column is one exeligmos apart, so they all cast shadows over approximately the same parts of the Earth. 
The longest duration of annularity was produced by member 20 at 12 minutes, 9 seconds on December 14, 1955. All eclipses in this series occur at the Moon’s ascending node of orbit.
Metonic series.
The metonic series repeats eclipses every 19 years (6939.69 days), lasting about 5 cycles. Eclipses occur in nearly the same calendar date. In addition, the octon subseries repeats 1/5 of that or every 3.8 years (1387.94 days). All eclipses in this table occur at the Moon's ascending node.
Tritos series.
This eclipse is a part of a tritos cycle, repeating at alternating nodes every 135 synodic months (≈ 3986.63 days, or 11 years minus 1 month). Their appearance and longitude are irregular due to a lack of synchronization with the anomalistic month (period of perigee), but groupings of 3 tritos cycles (≈ 33 years minus 3 months) come close (≈ 434.044 anomalistic months), so eclipses are similar in these groupings.
Inex series.
This eclipse is a part of the long period inex cycle, repeating at alternating nodes, every 358 synodic months (≈ 10,571.95 days, or 29 years minus 20 days). Their appearance and longitude are irregular due to a lack of synchronization with the anomalistic month (period of perigee). However, groupings of 3 inex cycles (≈ 87 years minus 2 months) comes close (≈ 1,151.02 anomalistic months), so eclipses are similar in these groupings.
Notes.
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