Saturday, Dec. 4, Total Solar Eclipse Closes 2021 Eclipse Quartet

Summary: The Saturday, Dec. 4, total solar eclipse closes the 2021 eclipse quartet as the second of the year's two solar eclipses.

Saturday, Dec. 4, 2021, total solar eclipse details; credit: Eclipse map/figure/table/predictions courtesy of Fred Espenak, NASA/Goddard Space Flight Center, from eclipse.gsfc.nasa.gov: No copyright, via NASA Eclipse Web Site

The Saturday, Dec. 4, total solar eclipse closes the 2021 eclipse quartet of two lunar eclipses and two solar eclipses as the second and last of the year's two solar eclipses.

December's solar eclipse is exclusively a southernmost Southern Hemisphere event. The path of totality for December's solar eclipse focuses continentally on West Antarctica and oceanically on the Southern Ocean, also known as the Antarctica Ocean or the Austral Ocean, and the southwesternmost reach of the South Atlantic Ocean.

The eclipse's path of partiality expands the event's visibility across the rest of Antarctica, known as East Antarctica or Greater Antarctica. The partial eclipse portion's northern limits visit the the south and subantarctic regions of the Atlantic Ocean and the Indian Ocean; skim southeastern Australia, southwestern Africa and southeastern South America; and sparingly touch the southwestern Pacific Ocean.

The instant of first external contact of the penumbra, the lunar shadow's outer and lighter portion, with Earth's surface initiates a solar eclipse's partial portion. According to the NASA Eclipse Web Site's eclipse predictions by NASA astrophysicist, now retired, Fred Espenak, the Saturday, Dec. 4, solar event's partial eclipse begins at 5:29:11.3 Universal Time (12:29 a.m. Eastern Standard Time; 2:29 a.m. Chile Summer Time; 4:29 a.m. Australian Eastern Daylight Time; 7:29 a.m. Central Africa Time and South Africa Standard Time).

The instant of first external contact of the umbra, the lunar shadow's innermost and darkest portion, with Earth's surface nudges the solar eclipse's total portion. The Saturday, Dec. 4, solar event's total eclipse begins at 7:00:01.0 UT (2:00 a.m. EST; 4:00 a.m. CLST; 6:00 a.m. AEDT; 9:00 a.m. CAT and SAST).

The instant of first internal contact of the umbra with Earth's surface occasion's the total eclipse's second significant umbral contact. This first internal umbral contact takes place at 7:05:48.9 UT (2:05 a.m. EST; 4:05 a.m. CLST; 6:05 a.m. AEDT; 9:05 a.m. CAT and SAST).

Greatest eclipse concerns the instant of closest passage of the lunar shadow cone's axis to Earth's center. The Saturday, Dec. 4, solar event's greatest eclipse takes place at 7:33:22.5 UT (2:33 a.m. EST; 4:33 a.m. CLST; 6:33 a.m. AEDT; 9:33 a.m. CAT and SAST).

The geographic coordinates at greatest eclipse are 76 degrees 46.7 minutes south latitude, 46 degrees 11.9 degrees west longitude. The coordinates place the Saturday, Dec. 4, greatest eclipse in the Weddell Sea, north of Berkner Island, also known as Berkner Ice Rise or Hubley Island.

At greatest eclipse, the moon's geocentric coordinates are right ascension of 16 hours 42 minutes 34.9 seconds and declination of minus 23 degrees 13 arcminutes 22.1 arcseconds. The sun's greatest eclipse geocentric coordinates are right ascension of 16 hours 43 minutes 32.3 seconds and declination of minus 22 degrees 16 arcminutes 29.3 arcseconds.

This greatest eclipse has a duration of 1 minute 54.4 seconds. At greatest eclipse, the path width measures 418.6 kilometers.

At greatest eclipse, the moon is in the constellation of Ophiuchus the Serpent Bearer, according to Fred Espenak's EclipseWise web site. Greatest eclipse precedes the lunar reach of perigee (Ancient Greek: περί, perí, “near” + γῆ, gê, “Earth”) by 0.1 days. According to Espenak's AstroPixels web site, perigee takes place Saturday, Dec. 4, 10:01 Greenwich Mean Time. The center-to-center distance of 356,794 kilometers between Earth and the moon qualifies as the year's minimum value, or closest distance, for perigee.

The instant of last internal contact of the umbra with Earth's surface marks the total eclipse's third significant umbral contact. This last internal umbral contact occurs at 8:00:40.9 UT (3:00 a.m. EST; 5:00 a.m. CLST; 7:00 a.m. AEDT; 10:00 a.m. CAT and SAST).

The instant of last external contact of the umbra with Earth's surface, which numbers as the total eclpse's fourth significant umbral contact, closes a solar eclipse's total portion. The Saturday, Dec. 4, solar event's total eclipse finishes at 08:06:29.2 UT (3:06 a.m. EST; 5:06 a.m. CLST; 7:06 a.m. AEDT; 10:06 a.m. CAT and SAST).

The instant of last external contact of the penumbra with Earth's surface terminates the partial solar eclipse. The Saturday, Dec. 4, solar event's partial eclipse ends at 9:37:23.9 UT (4:37 a.m. EST; 6:37 a.m. CLST; 8:37 a.m. AEDT; 11:37 a.m. CAT and SAST).

The end of the Saturday, Dec. 4, 2021, total solar eclipse marks the end of the year's eclipses. December's solar eclipse numbers as the fourth of the year's four eclipses and as the second of the year's two solar eclipses. The year's first solar eclipse took place Thursday, June 10, as an annular solar eclipse. The year's two lunar eclipses occurred Wednesday, May 26, and Friday, Nov. 19, as total and partial lunar eclipses, respectively.

The takeaways for the Saturday, Dec. 4, total solar eclipse are that it closes the 2021 eclipse quartet of two lunar and two solar eclipses; that the event's path of totality exclusively favors West Antarctica and the Antarctic Ocean; and that the event's path of partiality skims southernmost Africa, Australia and South America.

animation of total solar eclipse Saturday, Dec. 4, 2021: A.T. Sinclair/NASA, Public Domain, via Wikimedia Commons

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Saturday, Dec. 4, 2021, total solar eclipse details; credit: Eclipse map/figure/table/predictions courtesy of Fred Espenak, NASA/Goddard Space Flight Center, from eclipse.gsfc.nasa.gov: No copyright, via NASA Eclipse Web Site @ https://eclipse.gsfc.nasa.gov/SEplot/SEplot2001/SE2021Dec04T.GIF

animation of total solar eclipse Saturday, Dec. 4, 2021: A.T. Sinclair/NASA, Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:SE2021Dec04T.gif

For further information:

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