Total Solar Eclipse June 8, 1918, Was First of Two 1918 Solar Eclipses

Summary: The total solar eclipse June 8, 1918, was first of two 1918 solar eclipses, was a Northern Hemisphere event and was first in lineup of five eclipses.

Saturday, June 8, 1918, total solar eclipse details; credit: "Eclipse map/figure/table/predictions courtesy of Fred Espenak, NASA/Goddard Space Flight Center, from eclipse.gsfc.nasa.gov," via NASA Eclipse Web Site

The total solar eclipse June 8, 1918, was the first of two 1918 solar eclipses, was a Northern Hemisphere event and was also the first in the year's lineup of three lunar and two solar eclipses, of which the second solar eclipse was annular.

The June 1918 solar eclipse favored the Northern Hemisphere. The path of totality tracked, from its touchdown south of Japan, westward across the North Pacific Ocean; slanted across the United States from the Pacific Northwest to the South East's Florida; and then skimmed the North Atlantic Ocean for liftoff at the then-British crown colony of the Bahamas (independent Commonwealth of the Bahamas since Tuesday, July 10, 1973), according to a contemporary account in the Journal of the Royal Astronomical Society of Canada by Robert Millford Motherwell (1882-Sept. 30, 1940) of Ottawa's Dominion Observatory.

The expansive availability of the June 1918 solar eclipse's partial component contrasted with the elite corridor of the June 1918 solar eclipse's total component. The path of partiality included the areas of North America that were excluded from the path totality and also stretched across northeastern Asia and northern Europe, according to retired NASA astrophysicist Fred Espenak's EclipseWise website. The Arctic sprawl across Earth's upper northern latitudes also experienced the path of partiality, according to the Time and Date website.

Espenak's EclipseWise website also places the sun in Taurus the Bull constellation during the Saturday, June 8, 1918, solar eclipse and notes that lunar perigee preceded the event by 3.6 days. Lunar perigee (Ancient Greek: περί, perí, “near” + γῆ, gê, “Earth”) took place Wednesday, June 5 at 7:48 Coordinated Universal Time (3:48 a.m. Eastern Daylight Time), at a distance of 366,911 kilometers, according to computer programmer John Walker's Fourmilab Switzerland website.

The instant of first external contact between the lunar penumbra (shadow's lighter, outer region) and Earth's limb, designated as P1, initiates a partial solar eclipse. This first external penumbral contact took place Saturday, June 8, 1918, at 19:28:49.8 Universal Time (3:28 p.m. Eastern Daylight Time).

The instant of first external contact between the lunar umbra (shadow's dark center) and Earth's limb, designated as U1, starts a total eclipse. This first external umbral contact occurred at 20:31:31.4 UT (4:31 p.m. EDT).

Totality references a total eclipse's maximum phase, characterized by complete coverage of the solar disk by the lunar disk. Totality spans the first and last internal contacts of the lunar umbra with Earth's limb.

The instant of first internal contact between the umbra and Earth's limb, designated as U2, took place at 20:32:28.6 UT (4:32 p.m. EDT). This first internal umbral contact actually sequences as the second contact overall, as it is preceded by the first external umbral contact (U1).

Greatest eclipse defines as the instant of closest passage of the lunar shadow cone's axis to Earth's center. The Saturday, June 8, 1918, total solar eclipse's greatest eclipse happened at 22:07:22.9 UT (6:07 p.m. EDT).

Greatest eclipse occurred in the North Pacific Ocean, south of Alaska's Kodiak Island, at 50 degrees 50.9 minutes north latitude, 152 degrees 01.6 minutes west longitude. The path of totality at greatest eclipse had a width of 112.0 kilometers. The duration at greatest eclipse was 2 minutes 22.8 seconds.

The moon's geocentric coordinates at greatest eclipse were right ascension of 5 hours 4 minutes 40.4 seconds and declination of plus 23 degrees 17 arcminutes 39.0 arcseconds. The sun's geocentric coordinates were right ascension of 5 hours 4 minutes 40.0 seconds and declination of plus 22 degrees 50 arcminutes 23.8 arcseconds.

The instant of last internal contact between the umbra and Earth's limb, designated as U3, occurred at 23:42:20.2 UT (7:42 p.m. EDT). This last internal umbral contact sequences as the second and last internal umbral contact and as the third of the four contacts (two internal, two external) overall between the umbra and Earth's limb.

A total eclipse terminates at the instant of last external contact between the umbra and Earth's limb, designated as U4. This last external umbral contact numbers as the fourth and last of the four contacts overall between the umbra and Earth's limb. The Saturday, June 8, 1918, total solar eclipse ended at 23:43:12.3 UT (7:43 p.m. EDT).

The instant of last external contact of the lunar penumbra with Earth's limb closes a partial eclipse. For the Monday, June 8, 1918, solar eclipse, this last external penumbral contact occurred Tuesday, June 9, at 00:46:01.4 UT (Monday, June 8, at 8:46 p.m. EDT).

The June 1918 solar event's partial eclipse lasted for 5 hours 17 minutes 11.6 seconds. The June 1918 solar event's total eclipse had a duration of 3 hours 11 minutes 40.9 seconds.

The first photoelectric measurements of a total solar eclipse numbered among the achievements associated with contemporary scientific study of the Saturday, June 8, 1918, total solar eclipse, according to the University of Illinois at Urbana-Champaign's Sesquicentennial 1867-2017 Celebration website. American astronomer and University of Illinois at Urbana Observatory director Joel Stebbins (July 30, 1878-March 16, 1966) and Swiss-born American-naturalized University of Illinois theoretical physicist Jakob Kunz (Nov. 3, 1874-July 18, 1938) made the measurements as leaders of the Illinois Eclipse Expedition to Rock Springs, Wyoming.

The Saturday, June 8, 1918, total solar eclipse occurred as the first of 1918's two solar eclipses. The year's second solar eclipse took place Tuesday, Dec. 3, as an annular solar eclipse.

The takeaways for the June 8, 1918, total solar eclipse are that it was the first of two 1918 solar eclipses; that the path of totality favored the continental United States; that the eclipse occasioned the first photoelectric measurements of a total solar eclipse; that the photoelectric measurements were made by American astronomer Joel Stebbins and Swiss-born American-naturalized theoretical physicist Jakob Kunz; and that the year's second solar eclipse occurred almost six months later as an annular solar eclipse.

animated path of Saturday, June 8, 1918, total solar eclipse: Aug. 23, 2017: Tomruen, CC BY SA 4.0 International, 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, June 8, 1918, total solar eclipse details; credit: "Eclipse map/figure/table/predictions courtesy of Fred Espenak, NASA/Goddard Space Flight Center, from eclipse.gsfc.nasa.gov," via NASA Eclipse Web Site (https://eclipse.gsfc.nasa.gov/SEpubs/copyright.html) @ https://eclipse.gsfc.nasa.gov/SEplot/SEplot1901/SE1918Jun08T.GIF

animated path of Saturday, June 8, 1918, total solar eclipse: Aug. 23, 2017: Tomruen, CC BY SA 4.0 International, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Solar_eclipse_of_1918_June_8_animated_globe.gif

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