The Saros and the Solar Eclipse                           

In the space odyssey and forgotten sequel film, 2010: The Year We Make Contact, our lost astronaut, Dave Bowman, now an incorporeal being, re-appears on Earth to his widowed wife, Betty on her television screen and wishes her farewell. Before departing he explains to her that something is going to happen, “something wonderful.”

The year 2010 came and went without a cosmic bang but something wonderful did happen seven years later, and that “something” was the Great American Total Solar Eclipse of 2017! This cosmic contact put millions of watchers in the shadow of the Moon. But lucky for us in this country, we are again in store for another grand spectacle, the Great North American Total Solar Eclipse of 2024! After a 38 year drought on mainland USA prior to 2017, the Western Hemisphere is finally in the midst of a golden period for both American continents.

There are many opportunities to view solar eclipses both great and small from this hemisphere and abroad throughout the end of this decade. Here is a sample of Tom’s vacation list:                                          

Tom's Vacation List

New York City will mainly experience Partial Solar Eclipses (PSE) for most of these events, as it will not yet be in Umbral shadow path. The next Total Solar Eclipse seen from New York City is on May 1, 2079 but that could be a topic for another time. The well-advertised Solar Eclipses coming this year and next year will be visible as Partial Solar Eclipses: Oct. 14th 2023 (23% covered by the Moon) and then as a PSE on April 8th 2024 (90% covered by the Moon) As per my previous article on Eclipses, you want to be in the path of the Umbral Lunar shadow!

Make a special notation, for the very long duration of TSE 2027 and the 2028 Annular Solar Eclipse (ASE) as they are currently the longest in duration but will get progressively shorter as they each “age” throughout this century and beyond. This is what the Mesopotamic people understood centuries ago and they developed a method of predicting eclipses of what is called the Saros.


Saros 145 and the Great Millennium Solar Eclipses

You might notice from my vacation list a certain pattern, particularly the ones after the year 2025. The pairs of each solar eclipse in a calendar year fall back about ten days into the following year. That’s because a lunar year is about 354 days. A lunar year consists of twelve lunations. The lunation being a period averaging 29 ½ days from say, New Moon to New Moon. 

Going back to the Great American Total Solar Eclipse of 2017 and the one 18 years prior, called the Great European Eclipse of 1999 or probably best known as the Great Millennial Eclipse — as it was the last total solar eclipse of the Second Millennium. 

Being a similar eclipse to the one of Aug. 21, 2017; this eclipse prequel, on August 11, 1999, is when millions of Europeans got a chance to be in the shadow of the moon. The fact of the matter is, both eclipses are related; they are part of the same eclipse family — Saros 145. The name itself, sounding like part of a title from a science fiction movie.

Chaldeans were Mesopotamic people who kept good records of both lunar and solar eclipses from about 747 B.C. Over time they collected more records, and they began to see a long term rhythmic pattern from certain types of eclipse occurrences to the next event.  They noticed a pattern of 18 years and 10 ⅓ days or 11 ⅓ days where an eclipse had very similar characteristics to the one before. This is what would become to be known as the Saros. The term is a Greek word (σάρος) that was applied to the eclipse cycle by Edmond Halley in 1686.

In his remarkable book “Periodicity and variation of Solar (and Lunar) eclipses”  (2 volumes, ⓒ 1955), Dutch law professor and amateur astronomer, Dr. George van den Bergh arranged all 8,000 solar eclipses listed in Theodor von Oppolzer’s “Canon der Finsternisse” (ⓒ 1887) in a large array, called the Saros-Inex Panorama. Each column of this array includes a Saros family of eclipses, while each row lists an Inex family. One step down in the panorama means 1 Saros later and 1 step to the right is 1 Inex later. Van den Bergh numbers both the columns and rows of his array and so we have for the columns the numbers of the Saros families and for the rows those of the Inex families.


The Saros is useful for organizing eclipses into families or series. Every Saros series is assigned a number and starts out as partial eclipses near one of Earth’s polar regions. TSE 2017 and TSE 1999 are part Saros 145, which is nearing the middle of its life, as a maturing Saros. Its next appearance on Earth will be mainly over Asia and the Pacific Ocean on Sept. 2, 2035; which would be the 23rd out of a series of 77 for Saros 145. It started out as partial solar eclipse as seen from the North Pole on January 4, 1639, during the height of European colonization of the Americas. It then migrated southward and gradually became a Total Solar Eclipse on June 17, 1909. (see map below.)

Eclipse Map

Its current umbral duration is approaching almost 3 minutes. By the early part of the 26th century it will have reached its peak and will have an umbral duration of 7 minutes. It will cease being a TSE and revert to the partial phase in the year 2666. Its Penumbral shadow will for the last time touch the Earth’s South Pole on April 17, 3009! Who knows what kind of world we would have built by then.

Saros 145 Lifetime

There can be 40 Saros cycles running concurrently. At present, the range is from Saros # 117 to 156, the latter being the younger or newest of the Saros families. More on the Saros and Solar eclipses to come, particularly for the Great North American Total Solar Eclipse, Saros 139, the ultimate Solar Eclipse. 




Totality: Eclipses of the Sun, Fred Espenak, Mark Littman & Ken Willcox ⓒ 1999


Observe Eclipses, Michael Reynolds and Richard Sweetsir ⓒ 1995