Map of the world by Edward Stanford Limited marked with the paths of totality for the Saros cycle of … [+] eclipses from 1927-2164. The time and location of solar and lunar eclipses repeat themselves over a period of about 18 years. This series was discovered by Chaldeans over 2,500 years ago, and named by them the Saros. This map was modified by the drawing office of the Science Museum, London, for an exhibition held in 1927. The display at the Science Museum was to celebrate the total solar eclipse that was going to pass over North Wales and North West England that year. (Photo by SSPL/Getty Images)
SSPL via Getty Images
Go type annular into your word processing software. It got changed to annual, right?
The rare solar eclipse coming to North America on June 10, 2021 is one that commonly gets mis-named and, therefore, completely misunderstood.
So lets clear this up: there is no such thing as an annual solar eclipse.
What happens on June 10, 2021 will be an annular solar eclipse. Heres everything you need to know about the science that makes it happen:
XIAMEN, CHINA – JUNE 21, 2020 – An annular eclipse of the sun, photographed on the rooftop of the … [+] tallest hotel in kulangsu, Xiamen City, Fujian Province, China, June 21, 2020. – PHOTOGRAPH BY Costfoto / Barcroft Studios / Future Publishing (Photo credit should read Costfoto/Barcroft Media via Getty Images)
Barcroft Media via Getty Images
Annular means ring-shapedhence the colloquial term ring of fire (though ring of light is more accurate). During this event 89% of the Sun will be blocked by the Moonas seen from a path through Canada, Greenland and Russiato create a bright ring around the Sun. Much of northeast U.S. will see a big partial eclipse of the Sun around sunrise. Everyone will have to wear solar eclipses glasses and use solar filters on their cameras and telescopes.
So the annual thing is a complete mis-type or auto-correct? Dont solar eclipses happen every year? Well, actually, yes they dousuallybut there is no annual pattern whatsoever. Its way more intricate and incredible than that.
About every 18 months is usually whats quoted for the recurrence of a particular kind of solar eclipse, but thats not actually correct. Here are the annular solar eclipses coming up in the next decade:
- June 10, 2021
- October 14, 2023
- October 2, 2024
- February 17, 2026
- February 6, 2027
- January 26, 2028
- June 1, 2030
- May 21, 2031
You can see no pattern at all, right? And yet there is usually an annular solar eclipse every year or two. So whats going on?
How an annular eclipse appears depending on whether your location is in the antumbra or penumbra.
RAS/Lucinda Offer
Rather, eclipses of the Sun and Moon occur every SarosGreek for cycle. A Saros lasts for 6,585 days18 years, 11 days and eight hours. Every Saros the Sun, Moon and Earth come full circle and for a few brief minutes they line-up to cause a spectacular totality (or annularity, which depends on the distance of the Moon from Earth).
The eclipses in the same Saros throw a shadow onto the Earth thats incredibly similar in geometry. The 18 years, 11 days difference means their date drifts 11 days forward for each subsequent eclipse, and the eight hours means that the Earth rotates a third, so the path shifts roughly 120º west.
MORE FROM FORBESWhere Were You 18 Years, 11 Days And 8 Hours Ago? Meet The Eclipse-Chasers Who Live By The ‘Saros’By Jamie CarterThis pattern repeats, though each Saros begins as a set of repeating partial solar solar eclipses, then becomes annular, then total, then annular, then partial again before fizzling out. This process takes centuries.
Lets take this weeks solar eclipse on June 10, 2021 as an example. Its an annular solar eclipse and its a member of Saros 147. Its been causing eclipses since 1624 and will do so until 3049. Heres what its been doing, and will do, in our immediate erawith each event exactly 18 years, 11 days and eight hours apart:
- May 31, 2003: annular solar eclipse (Greenland, Iceland, northern Scotland)
- June 10, 2021: annular solar eclipse (Canada, Greenland, Russia)
- June 21, 2039: annular solar eclipse (Alaska, northern Canada, northern Scandinavia)
You can see the pattern in the dates, above, and the westward drift of the paths of annularity.
Its exactly the same process for total solar eclipses, which are from a Saros that is currently producing totalities.
In the same way, the totality experienced by 12 million Americans on August 21, 2017s Great American Eclipse was part of Saros 145, so was witnessed 18 years, 11 days and eight hours previously on August 11, 1999 in the U.K. and Europe. Almost precisely the same shadow across Earth will fall on September 2, 2035, but this time on China, Japan and the Pacific Ocean.
So when youre watching a solar eclipse, remember that its part of a pattern thats far larger than a human lifespan. It repeats through the ages, almost like a mathematical heartbeat as our Sun, Moon and Earth come full circle.
Disclaimer: I am the Editor of WhenIsTheNextEclipse.com
Wishing you clear skies and wide eyes.