"It is always exciting when the moon eclipses the sun, but the eclipse of June 1 will be seen by few people, because it will be visible only from Arctic and other extreme northern regions," said eclipse expert Jay Pasachoff of Williams College in Massachusetts.

Solar eclipses occur when Earth, the moon, and the sun are aligned so that—as seen from Earth—the moon appears to cover all or part of the sun's disk.

Partial solar eclipses, such as tonight's, which is the second of 2011—happen when Earth crosses only through the faint outer part of the moon's shadow, known as the penumbra. (See pictures of January's partial solar eclipse.)

By contrast, during a total eclipse the sun is completely