Apr
14
2014

Tonight's total lunar eclipse is first of four in a row

Lunar eclipse: Tonight's will be the first in a tetrad of four total lunar eclipses over the next year-and-a-half.
Lunar eclipse: Tonight's will be the first in a tetrad of four total lunar eclipses over the next year-and-a-half.Courtesy Mark Ryan
The first of 4 consecutive total lunar eclipses occurs late tonight (and early Tuesday morning) and will be visible to practically all of the United States (local weather permitting). The astronomical event begins around 5:58 UT, and should last about 4 and a half hours from start to finish.

A total lunar eclipse takes place when the moon passes through the Earth's umbra, the innermost darkest shadow created by the Earth as it (from the Moon's perspective) blocks out the Sun. Refraction caused by the Earth's atmosphere allows for some of the Sun's light to bend around the Earth and bathe the Moon in an amber glow, resulting in what is sometimes referred to as a Blood Moon, especially by some fundamental religious groups who see it as an omen of the biblical End Times. There are two other kinds of lunar eclipses. When the Moon passes only through the penumbra, the faint part of the shadow, that's called a penumbral lunar eclipse. When only a portion of the Moon intersects with the darker umbra, that's a partial lunar eclipse.

As I mentioned, tonight's eclipse is the first in a series of four consecutive total lunar eclipses. This is a pretty uncommon occurrence known as a tetrad. Only 62 tetrad events will have occurred from 1 A.D. to the year 2100, and just eight in the 1200 months of the 21st century.

Each year there are at least two lunar eclipses and sometimes as many as five. Eclipses don't happen every month because the plane of the Moon's orbit around Earth is tilted. Usually, consecutive eclipses are a mix of partial, penumbral, and the relatively rarer total lunar eclipses. To have four total lunar eclipses happen in a row, as we will over the next seventeen months or so is even rarer. And luckily, all four of them be will visible to most of us in the United States.

Tonight's celestial event begins at 11:55 PM (Minneapolis time) and reaches maximum eclipse at 2:46 AM, then finishes at 4:32 AM. If you want to confirm the times for your area, use this handy eclipse calculator. The night-owl timing of tonight's eclipse might keep many of you from enjoying it (I'll probably be sleeping), but just know there are three more headed our way: October 8, 2014, April 4, 2015, and September 28, 2015.

SOURCES and LINKS
NASA Eclipse Web Site
Eclipse expert Fred Espanek's Lunar Eclipse Primer
Universal Time (UT) conversion table
Observing tips at Space.com
Eclipse visibility maps at Space.com

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