An image of the sun resembles a winking eye in the shadow of a pair of bifocals during an annular eclipse over India in January 2010. In addition to partial eclipses, a given year may see two other types of solar eclipses: total and annular.
During a total eclipse, the moon completely blots out the sun, casting its dark central shadow, called the umbra, onto a very narrow strip along Earth's surface. (See pictures of the most recent total solar eclipse, over Easter Island.) An annular eclipse happens when the moon covers only the central part of the sun's disk, leaving a ring of sunlight still visible.
This year will be unusual, because there will be no total or annular eclipses, just partials, said Pasachoff, the Field Memorial Professor of Astronomy at Williams College in Massachusetts.
"That hasn't happened since 1982 and won't happen again until 2029," he said.