This question was left over from the last question I had, so I am asking it separately here:
I have been looking into two solar eclipses (Saros series 147 and 152) that will both be occurring in 2021. Each of these eclipses will be happening near the opposite poles of the earth. Both are part of young saros series. Saros 152 is comprised of 70 eclipses, while saros 147 contains a total of 80 eclipses. These series are 10 eclipses difference in length and began 180 years apart. So, I happened to check out their ending dates and found that both series are projected to end during the exact same year - 177 day apart – together in the year 3049. I thought that both of these series ending together one semester apart in the very same year was a pretty amazing coincidence.
So, checking further – it seems new saros series start from as few as 7 years apart to as many as 100 years apart (this is extremely variable spacing, but it averages to about 31 years apart over the usual 1260+ year active series lifespan). I wanted to know why series 147 and 152 would both be ENDING at the same time. I went back to the NASA website, and checked the 5000 year listing of all solar saros series numbering 0 through 180. I only found one other such instance of two solar saros series ENDING in the same year – series 49 and 54 both ENDED together in 32 CE – so it seems like a pretty rare event.
But then, I checked to see if there were any occasions of two saros series BEGINNING together in the same year. Going back to the NASA website again with this question, I checked the 5000 year listing of all solar saros series numbering 0 through 180. I only found one single example of two saros series both BEGINNING in the same year. This time series 142 and 147 both BEGAN together in the year 1624 CE.
Not only is solar saros 147 involved in BOTH of these "same year" cases, but all three series eclipses will be presenting themselves during a single upcoming semester series in 2021 – solar series 142 (Dec 14, 2020), 147 (June 10, 2021), and 152 (Dec 4, 2021).
Can anyone explain to me the actual mechanics behind what causes saros series to begin and end? I am familiar with Saros/Inex Panorama – but unfortunately they do not answer this question, and I can’t even read them online anyway.
Does anyone know why solar saros 147 may have STARTED in the same year as saros 142 or why saros 147 will be ENDING together in the same year as saros 152? Are these two occasions both very rare coincidences, while at the same time, both involve the same series 147?