A total solar eclipse occurred at the Moon's descending node of orbit on Thursday, July 11, 1991,[1] with a magnitude of 1.08. 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. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide. Occurring only about 8 hours after perigee (on July 11, 1991, at 11:00 UTC), the Moon's apparent diameter was larger.[2]
The eclipse lasted for 6 minutes and 53.08 seconds at the point of maximum eclipse. There will not be a longer total eclipse until June 13, 2132. This was the largest total solar eclipse of Solar Saros series 136. This eclipse was the most central total eclipse in 800 years, with a gamma of −0.00412. There will not be a more central eclipse for another 800 years. Its magnitude was also greater than any eclipse since the 6th century.
Totality began over the Pacific Ocean and Hawaii, moving across Mexico, down through the Central American countries of Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica and Panama, across Colombia and ending over Brazil. A partial eclipse was visible for parts of southern Canada, the United States, Mexico, Central America, the Caribbean, and South America.
An observation team funded by the National Natural Science Foundation of China made near-infrared spectroscopic observations in the southern suburbs of La Paz, Baja California Sur, Mexico. Weather was clear on the eclipse day in La Paz. The team captured dozens of frames of the slitless spectrum of the upper layer of photosphere and chromosphere, and the slit spectrum outside the solar surface. They also captured images of the chromosphere and solar prominences. Among the professional observation teams from various countries to La Paz, six used the new CCD sensors for the first time in solar eclipse observation. Among them, the Chinese and Japanese team used it to observe long-wavelength spectra.[3] A team of 320 people from NASA's Johnson Space Center made observation in Mazatlán, Mexico. The local weather was not ideal in the days before the eclipse, but got slightly better as the eclipse day approached. Some people went to San Blas, Nayarit for better weather conditions. In the end, a hole in the clouds appeared in El Cid in western Mazatlan, through which the corona and prominences was visible. Other observers 1 to 5 miles away were clouded out. In San Blas, the corona and prominences were still visible, even though the clouds became thicker during totality.[4] Scientists from the Royal Observatory of Belgium, the Institute of Geodesy and Geophysics of the Chinese Academy of Sciences, and the Institute of Geophysics of the National Autonomous University of Mexico made observations in Mexico City to study the change in gravity during a total solar eclipse.[5]
The American ethnographer and anthropologist Victoria Bricker and her late husband and colleague Harvey Bricker, claim in their book "Astronomy in the Maya Codices" that by decoding pre-Columbian glyphs from the four Maya codices they discovered that pre-16th century Maya astronomers predicted the solar eclipse of July 11, 1991.[6] In their 2011 volume, the husband-wife Brickers team explain how they translated the dates from the Maya calendar, then used modern scientific knowledge of planetary orbits to line up the data from the Maya prediction with the Gregorian calendar.[7] Reviewers disputed the claim in 2014, concluding that, "loose hieroglyphic readings and accommodating pattern matching occurs throughout the book."[8]
The 1991 eclipse appears in the music video for Cosas del Amor, a duet by Vikki Carr and Ana Gabriel.[9]
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.[10]
| First Penumbral External Contact | 1991 July 11 at 16:29:42.3 UTC | |
| First Umbral External Contact | 1991 July 11 at 17:22:36.8 UTC | |
| First Central Line | 1991 July 11 at 17:24:13.8 UTC | |
| First Umbral Internal Contact | 1991 July 11 at 17:25:50.7 UTC | |
| First Penumbral Internal Contact | 1991 July 11 at 18:18:45.5 UTC | |
| Greatest Duration | 1991 July 11 at 19:01:51.6 UTC | |
| Greatest Eclipse | 1991 July 11 at 19:07:00.8 UTC | |
| Ecliptic Conjunction | 1991 July 11 at 19:07:03.3 UTC | |
| Equatorial Conjunction | 1991 July 11 at 19:07:07.0 UTC | |
| Last Penumbral Internal Contact | 1991 July 11 at 19:55:15.7 UTC | |
| Last Umbral Internal Contact | 1991 July 11 at 20:48:11.3 UTC | |
| Last Central Line | 1991 July 11 at 20:49:47.8 UTC | |
| Last Umbral External Contact | 1991 July 11 at 20:51:24.3 UTC | |
| Last Penumbral External Contact | 1991 July 11 at 21:44:20.2 UTC |
| Eclipse Magnitude | 1.07997 | |
| Eclipse Obscuration | 1.16633 | |
| Gamma | −0.00412 | |
| Sun Right Ascension | 07h22m12.8s | |
| Sun Declination | +22°05'48.5" | |
| Sun Semi-Diameter | 15'43.9" | |
| Sun Equatorial Horizontal Parallax | 08.7" | |
| Moon Right Ascension | 07h22m12.5s | |
| Moon Declination | +22°05'33.9" | |
| Moon Semi-Diameter | 16'42.1" | |
| Moon Equatorial Horizontal Parallax | 1°01'17.7" | |
| ΔT | 57.9 s |
See also: Eclipse cycle. 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. The first and last eclipse in this sequence is separated by one synodic month.
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