Most of the United States will see a rare astronomical alignment late today: a partial solar eclipse. And across a narrow swath of the western U.S., the eclipse will be even rarer — the Moon will be completely enfolded within the Sun’s disk, leaving a thin but bright ring of sunshine around the Moon.
A similar eclipse took place on May 10th, 1994, although this one is shifted about a third of the way westward around the globe. And in fact, the two eclipses are like cousins — both are members of an eclipse “family,” known as a Saros.
We’re all familiar with the Moon’s month-long cycle of phases. But the Moon also has other cycles — its distance from Earth and its relation to the Sun’s path across the sky, among others. Three of these cycles overlap every 6,585-and-a-third days — a bit more than 18 years. When they overlap, there’s an eclipse.
Each Saros cycle lasts for centuries. It begins with partial eclipses that are visible from one of the poles, then moves across Earth’s disk with total or annular eclipses, then finishes with more partial eclipses at the opposite pole.
Today’s eclipse is part of Saros cycle 128. The first eclipse in the series took place in the year 984, and the last will be in 2282.
The annular part of today’s eclipse begins around 6:24 p.m. Pacific Time, at the California-Oregon border. It ends at 8:39 p.m. Central Time, as the Sun and Moon set over western Texas.
Script by Damond Benningfield, Copyright 2012