On Sunday evening, the eclipse will march from Oregon and California to Nevada, Utah, New Mexico, Arizona and Texas.
- The annular eclipse will begin in the morning for Japan and China, and end in the evening for some U.S. states.
- An annular eclipse occurs when the moon blocks the sun, but a bright ring of sunlight remains.
- The event will be the first time in 18 years that such an eclipse is visible from the continental U.S.
At sunrise in some parts of China and Japan and by sunset in the western United States, a partial solar eclipse is set to slink across a narrow swath of the Earth on May 20 and 21.
Depending on where people are in the eclipse's path, some may be able to witness an annular eclipse in which the moon blocks out all but a ring of the sun's light.
Others will see the sun as a crescent, for a period of around four to five minutes.
The event will be the first time in 18 years that such an eclipse is visible from the continental United States, according to Fred Espenak, a longtime solar eclipse expert with NASA.