‘Pink Moon’ turns ‘blood moon’ red in full lunar eclipse (Photo gallery coming)

This was the first of four consecutive full lunar eclipses known as a tetrad.

The upcoming eclipse, which is being referred to as a “blood moon,” is the first in a series of four – called a tetrad – that will occur throughout 2014 and 2015 in six-month intervals. The more or less “official” nickname for tonight’s full moon is the Pink Moon, but in the wee hours of Tuesday morning it will take a decidedly reddish-orange hue when a full lunar eclipse turns it into a “blood moon.”

Eclipses only occur about twice a year, and NASA has confirmed that the tetrad has only occurred three times in the last 500 years. The blood moon phenomenon is being called a rare occurrence by many people, but others speculate that this event could be an apocalyptic sign from the heavens; we’ll let you pick the side you want to be on.

Just as the famed Blue Moon isn’t blue, the Pink Moon — except for evenings like this — isn’t pinker in color than any other full moon. The nickname was given to the April full moon by Native Americans, who associated it with the appearance of blooming moss pink (wild ground phlox). Other names for the April full moon are the Sprouting Grass Moon, the Egg Moon, and the Fish Moon.

Lunar eclipses occur when the Sun, Earth and moon are lined up so that the moon passes through all or part the Earth’s shadow, blocking sunlight from the lunar surface facing the sun. The term blood moon comes from the reddish-orange hue that comes from the longer red light waves from the sun that ring the Earth as the moon passes through its shadow during a full eclipse.

While lunar eclipses are common, it is unusual for four full eclipses to come in succession like this, known as a tetrad. NASA officials say that because of the eccentricity of the Earth’s orbit and the timing of the eclipse seasons, there are long periods when they don’t appear at all. There were no tetrads from 1582 until 1908, NASA officials say, but there will have been 17 tetrads between 1909 and 2156.

The last tetrad was in 2003-04, while the next will occur in 2032-33, NASA officials say.

But they won’t always be with us. As the eccentricity of the Earth’s orbit continues to lessen, in the distant future tetrads will not be possible.

During the 5000-year period from 1999 B.C. to 3000 A.D., there are 4,378 penumbral eclipses (36.3 percent), 4,207 partial lunar eclipses (34.9 percent) and 3,479 total lunar eclipses (28.8 percent), according to information from NASA. Approximately 16.3 percent (568) of all total eclipses during that period will belong to one of the 142 tetrads occurring over those 5000 years.

 

Some also are seeing a religious overtone in tonight’s eclipse because it falls on Passover, which starts at sundown this evening (8:04 p.m.). Passover was the night that Israelites enslaved in Egypt placed lamb’s blood over the door of their homes so that the Angel of Death, sent to kill the firstborn sons of their Egyptian captors and prompt the Israelites’ release from bondage, would know to bypass their homes.

Click here to view the moon seen from around the world on Mashable.