The Moon slips through Earth’s long shadow early tomorrow, creating a total lunar eclipse — but just barely. The Moon will pass through the edge of the shadow, so the total portion of the eclipse won’t last long. Almost all of the United States will see at least part of the eclipse.

Lunar eclipses occur only at full Moon, when the Moon lines up opposite the Sun. The Moon’s orbit is tilted, though. So most months, the Moon passes above or below Earth’s shadow, so there’s no eclipse.

But the dark inner portion of the shadow, which creates both total and partial eclipses, is about three times the Moon’s diameter, so it’s a big target. The Moon can stray from a precise alignment with the Sun and still dip into the shadow.

That’s what happens tonight. The Moon will slip into the edge of the shadow as seen from Earth, so it’ll be fully darkened. But the edge of the shadow will be just off the edge of the lunar disk. As a result, the total eclipse will last only slightly longer than the shortest possible duration.

The partial eclipse — when only part of the lunar disk is in the shadow — begins at 4:45 a.m. Central Time. The Moon will be fully eclipsed by 6:11. Totality will end about 15 minutes later. From roughly the eastern half of the U.S., the Moon will set before the total eclipse begins. The western U.S., including Hawaii and Alaska, will see all of the total eclipse, and all or most of the partial eclipse.

Script by Damond Benningfield

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