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Rare ‘blood moon’ kicks off lunar eclipse tetrad PDF Print E-mail
Sunday, April 13, 2014 8:00 PM

BY STEPHANIE GROVES

Staff Writer

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According to National Geographic, it’s been two years since skygazers witnessed a total lunar eclipse, which will be visible above the Western Hemisphere in the early hours Tuesday.

Observers will have a spectacular vista as the Earth’s shadow creeps across the full moon painting it a coppery-red color and creating what some call a “blood moon.”

This astronomical event kicks off a lunar eclipse tetrad (group of four) in a row, which is a rare occurrence. A total of three total lunar eclipses will appear over the Western Hemisphere every six months; one on October 8 this year and April 4 and September 28 in 2015.

The last tetrad series happened in the years 2003 and 2004 and will only occur seven more times in the current century.

The eclipse will last over three and a half hours, starting at 12:58 a.m. Eastern Daylight Time (EDT) when the moon begins to plunge into the umbra, the darkest center of the Earth’s shadow.

The best part of eclipse will be during totality, starting at 3:07 a.m. EDT and lasting 78 minutes. After that, Earth’s shadow begins to leave the surface of the moon.

During this eclipse, refracted sunlight shines through the ring of Earth’s dusty and cloudy atmosphere and casts the red part of the spectrum onto the moon’s surface. This results in transforming the dark gray color of the moon during the partial phase of the eclipse to a reddish-orange or copper color during totality. The same effect occurs when the sun turns red at sunset.

The moon’s color during totality can vary depending on the amount of dust in the Earth’s atmosphere. For example, if there are active volcanic eruptions emitting tons of ash into the upper atmosphere, it can trigger blood-red eclipses.

Lunar eclipses occur only when there is a full moon and the sun, Earth and moon are aligned perfectly for the Earth’s shadow to turn out the lunar lights. During a full lunar eclipse, the moon passes behind the Earth which blocks the sun’s rays from striking the moon.

Because of the moon’s tilted orbit around the Earth, eclipses don’t occur every month; instead, it usually happens once every few years. Occasionally, there are more than one in a year.

Unlike solar eclipses, lunar eclipses are safely visible to the naked eye.

Lunar eclipses are not always seen in the skies over heavily populated cities and towns, which makes Tuesday’s event very special for skywatchers.

Observers will also see Spica — the bright star in the constellation Virgo — which will appear very close to the moon during the eclipse and the orange-hued Mars, which will be shining bright off to the west.

 

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