Monday, June 12, 2017

2017 Eclipse Corner #2 The Moon Orbit

The Moon is our most obvious viewable space neighbor and its daily changing phases are remarkable. The Moon produces no light, it simply reflects light from the Sun. Ancient farmers knew the best time to plant different crops and the best time harvest options based on the Moon. Today, the Farmer’s Almanac is still available for those farming facts. As the Moon orbits the earth, its path moves from west to east, changing position among the background stars.. It takes the Moon 29 ½ days to complete a revolution around the earth. That is how the calendar month was developed.
Lunar Phases

http://spaceplace.nasa. gov/review/dr-marc-earth/moon-phases.html

The Sun illuminates half the Moon at all times, but the earth’s position to the plane of the Sun-Moon allows us to see different “phases.” Following the picture, when the Moon is in line with the Sun the illuminated side of the Moon is opposite the earth. We do not see the Moon. This phase is called the New Moon. As the Moon moves in its revolution each day we see the phase getting larger or showing more light.  This is called waxing. After the Full Moon, the phases get smaller or show less light which is called waning until we get back to the New Moon phase. Phases include; New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Third or Last Quarter, and Waning Crescent. The Moon will rise about 50 minutes later each day. Full Moon is always opposite the Sun which would be setting as the Full Moon rises.

When the Moon is at the New Moon phase, it is between the earth and the Sun and this could produce a Solar Eclipse. When the Moon is at the Full Moon phase, the earth is between the Moon and the Sun and could produce a Lunar Eclipse by producing the earth’s shadow across the Moon. These lunar positions do not always cause an eclipse because the Moon also moves an angle of 5 degrees up or down to the Earth-Sun plane. Only when the Moon is at the “line of the nodes” or in alignment with the Earth-Sun plane will eclipses be possible.

This picture simply shows the 5 degrees out of alignment the Moon can be for eclipses. The distances and angles are exaggerated. The line of the nodes is the Earth- Sun plane.

The Moon is often seen in the daytime as well. From new Moon to Full Moon the Moon is rises in the daytime starting at the new moon phase and that lasts until the Full Moon phase where the Sun sets as the Moon rises. The waning phases have the Moon rising in the night time. As the cycle is completed, it starts over. Luckily, we get the Moon at the “line of the nodes” or perfect alignment with the Earth-Sun plane on August 21, 2017,which will produce our fantastic Total Solar Eclipse. Eclipse Corner will present more astronomy facts to get you ready for the eclipse. –Dan Slais

Join us August 18-21, 2017 for Midnight at Noon a four day music festival and eclipse viewing event.  For more information visit our website at 

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