What to watch for on April 8^th as totality sweeps across the continent.

The time has come. Seven years ago on an August afternoon, the shadow on the Moon swept across the United States. Now we’re in the one month stretch, leading up to the big ticket astronomical event for 2024: the April 8^th total solar eclipse spanning North America.

This is the last total solar eclipse for the ‘lower 48 states’ until August 23^rd, 2044. Totality does nick remote northwest corner of the state of Alaska on March 30^th, 2033. The path of totality on April 8th spans Mexico, the contiguous United States from Texas to Maine, and the Canadian Maritimes.

The eclipse will be partial from southeast Alaska, all the way down to the very northwest edge of South America. Hawaii will see a rising partial. On the other end, Iceland and the very western coast of Ireland will see the reverse underway at sunset.

A Penumbral Prelude

The first eclipse season of 2024 actually begins on the night of Sunday/Monday March 24/25. A penumbral lunar eclipse that night puts the whole celestial game into play. This subtle eclipse is visible from the Americas. Don’t expect to see much more than a slight ragged darkening on the southwest limb of the Moon around 7:12 Universal Time.

Though it’s a slight affair, this penumbral eclipse means that the nodes where the Moon’s path intersect the ecliptic are aligning for the total solar eclipse two weeks later. Though the 2017 event was an ascending node eclipse, the 2024 one is a descending node event, crisscrossing the path.

Tales of the Saros

This eclipse is member 30 of the 71 eclipses in solar saros series 139. This saros began way back on May 17^th, 1501, and produced its first fully total solar eclipse (as opposed to a hybrid annular-total) on December 21^st, 1843. It’ll cease doing so with the brief total solar eclipse of March 26^th, 2601, and finally end on July 3^rd, 2763.

One famous alumni for saros 139 occurred one exeligmos (three saroses or 54 years) ago on March 7^th, 1970. This eclipse moved right up the U.S. East Coast in a path just slightly east of the upcoming eclipse. The three saros period is crucial, as each pass shifts the path 120 degrees in longitude westward, and three brings it nearly back around the globe full circle. The 1970 eclipse is one of two suspects referenced in Carly Simon’s song You’re so Vain… and the April 8^th eclipse passes over the very tip of northern Nova Scotia. Will someone once again take their “Learjet to Nova Scotia, to see a total eclipse of the Sun?”

To be sure, we enjoy living in an epoch on a planet where total solar eclipses can occur… but this won’t always be the case. The Moon is slowly receding from the Earth, meaning that in about 600 million years time, all solar eclipses will be partial or annular only. Already, in the current 5,000 year epoch, annulars are now more common than totals. We’re also not the only place in the solar system where you could stand and see a moon versus the Sun in a close fit; the surfaces of the Jovian moons witness something similar about twice a decade.

Chasing the Shadow of the Moon

On Monday April 8^th, the action begins when the penumbral (partial) shadow of the Moon first touches down over the South Pacific at 15:42 Universal Time (UT). Then, the inner umbral shadow touches down over the south-central Pacific at 16:42 UT, sweeping its way to the northeast. The shadow then first makes landfall over the…