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How Often Do Seven Eclipses Occur in One Year?




Seven Eclipses In One Calendar Year

It is quite rare to have seven eclipses in one calendar year. This last happened in the year 1982 and won't happen again until the year 2038. After 2038, it won't be until the year 2094.


At left: illustration a solar eclipse at new moon. At right: lunar eclipse at full moon.

Seven eclipses occur in a minimal period of 12 lunar months (approximately 354.37 days). Because one lunar year (12 lunar months) is only about 11 days shorter than one calendar year, the first of seven eclipses has to come in early January in order for the last one to occur before the year's end.


By the way, one lunation - or lunar month - refers to the period of time between successive new moons or successive full moons, a mean period of 29.53059 days. The lunar phase cycle is also known as the synodic month.


We list the seven eclipses for the years 1982 and 2038. In each case, a pair of eclipses comes at the beginning and the end of the year, and an eclipse triplet occurs in one lunar month during the middle part of the year. At each eclipse cycle, lunar and solar eclipses are separated by one fortnight (two-weeks time):



1982 (Seven eclipses: 4 solar/3 lunar)

2038 (Seven eclipses: 3 solar/4 lunar)


Jan 09 lunar eclipse

Jan 05 solar eclipse

Jan 25 solar eclipse

Jan 21 lunar eclipse


Jun 21 solar eclipse

Jun 17 lunar eclipse

Jul 06 lunar eclipse

Jul 02 solar eclipse

Jul 20 solar eclipse

Jul 16 lunar eclipse


Dec 15 solar eclipse

Dec 11 lunar eclipse

Dec 30 lunar eclipse

Dec 26 solar eclipse


For a more in-depth discussion on the number of eclipses in a calendar year, please read How many solar and lunar eclipses in one calendar year? Now to explore how often seven eclipses take place in one year's time, not the confines of one calendar year. . .




Seven Eclipses In One Year's Time


Some might argue that the calendar year is an artificial constraint, and that our focus should be on how often seven eclipses happen within the framework of one lunar year, or 12 lunar months (approximately 354 days). The lunar year is about 11 days shy of one year's duration, so seven eclipses in 12 lunar months easily fall within the bounds of one year.


Image at right depicts a total solar eclipse(A), annular solar eclipse (B) and a partial solar eclipse (C)

Using our new parameters, we last had seven eclipses in one year during the stretch of time from November 13, 2012, to November 3, 2013. Seven eclipses will next happen in one year from January 31, 2018, to January 21, 2019. In short, any time a lunar month sports three eclipses, we have seven eclipses in one year.


We list the seven eclipses that take place in a period of one year in 2012-13 and 2018-19. The table seeks to illustrate why three eclipses in one lunar month guarantee seven eclipses in the span of a year.



2012-13 (Seven eclipses: 3 solar/4 lunar)

2018-19 (Seven eclipses: 4 solar/3 lunar)


2012 Nov 13 solar eclipse

2018 Jan 31 lunar eclipse

2012 Nov 28 lunar eclipse

2018 Feb 15 solar eclipse


2013 Apr 25 lunar eclipse

2018 Jul 13 solar eclipse

2013 May 10 solar eclipse

2018 Jul 27 lunar eclipse

2013 May 25 lunar eclipse

2018 Aug 11 solar eclipse


2013 Oct 18 lunar eclipse

2019 Jan 06 solar eclipse

2013 Nov 03 solar eclipse

2019 Jan 21 lunar eclipse


Seven Eclipses Recur After One Saros Period


Eclipses often recur every 223 lunar months, or in a period of 18.03 years. This is the famous Saros period of 18 years and 11.32 or 10.32 days, depending on the number of intervening leap years.


Photo credit: Stephen Bratman

Seven eclipses take place in one lunar year of 12 months from Dec 14, 2001 to Dec 4, 2002. These eclipses recur one Saros period (18.03 years) later, from Dec 26, 2019 to Dec 14, 2020. The table below helps to illustrate how these eclipses repeat after one Saros period.


Once again, if you have three eclipses in one lunar month, you'll get seven eclipses in one year. In our two examples, a pair of eclipses comes before the eclipse triplet, and a pair of eclipses follows the eclipse triplet, for a grand total of seven eclipses in 12 lunar months.


Eclipses always come in pairs or, less commonly, in triplets, with a solar eclipse always happening within a fortnight of a lunar eclipse - and vice versa.


Seven Eclipses Separated By One Saros Period



2001-02 (Seven eclipses: 3 solar/4 lunar)

2019-20 (Seven eclipses: 3 solar/4 lunar)


2001 Dec 14 solar eclipse

2019 Dec 26 lunar eclipse

2001 Dec 30 lunar eclipse

2020 Jan 10 solar eclipse


2002 May 26 lunar eclipse

2020 Jun 05 lunar eclipse

2002 Jun 10 solar eclipse

2020 Jun 21 solar eclipse

2002 Jun 24 lunar eclipse

2020 Jul 05 lunar eclipse


2002 Nov 20 lunar eclipse

2020 Nov 30 lunar eclipse

2002 Dec 04 solar eclipse

2020 Dec 14 solar eclipse


However, in between the the seven-eclipse years listed above, seven eclipses happen in one lunar year (and less than one-year's time) on four other occasions. We place these seven-eclipse years in their proper places in between the two mentioned above:


Dec 14, 2001 to Dec 4, 2002

Jan 26, 2009 to Jan 15, 2010

Dec 21, 2010 to Dec 10, 2011

Nov 13, 2012 to Nov 03, 2013

Jan 31, 2018 to Jan 21, 2019

Dec 26, 2019 to Dec 14, 2020


Nineteen-year Metonic Cycle Oversees 6 Years Containing Seven Eclipses


We find that seven eclipses take place within the framework of single year for a total of 6 times during this particular 19-year period from Dec 14, 2001, to Dec 14, 2020. This 19-year period of 235 lunar months is known as the Metonic cycle, whereby the phases of the Moon fall on or near the same calendar dates every 19 years.


Photo of annular solar eclipse: Brocken Inaglory

It appears that one Saros period of 18.03 years commonly produces 5 seven-eclipse years. Based on that alone, I think it's safe to say that seven eclipses happen in one year fairly frequently.


If I counted up everything correctly, seven eclipses happen in a year's-time a total of 28 times in the 21st century (2001 to 2100). The illustration below shows why it's inevitable that each eclipse season, coming in cycles of 173.3 days, and lasting approximately five weeks, has a minimum of two eclipses, and a maximum of three.


Eclipse Seasons Come Every 173.3 Days


Although the Moon's orbit around Earth is inclined at 5o to Earth's orbit around the Sun, the Moon crosses the Earth's orbital plane twice a month at points called nodes. Every 173.3 days, the line of nodes points at the Sun, and it's the middle of the approximate five-week eclipse season (highlighted in gray). During any eclipse season, there are always one solar eclipse and one lunar eclipse, each of which occurs within one fortnight of the other. If the first eclipse arrives early enough in the eclipse season, three eclipses then take place within one lunar month, and it's inevitable that seven eclipses occur in one year's time.

Resources:


Catalog of Solar Eclipses 2001 to 2100


Catalog of Lunar Eclipses 2001 to 2100


copyright 2014 by Bruce McClure

May 2014 Feature * July 2014 Feature