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Lunar Eclipse Coming Soon

This article appeared in the December 3, 2010 edition of the Davis Enterprise.

Everyone is invited to the Astronomy Club meeting tomorrow night at Explorit's Nature Center (3141 5th Street) starting at 7:00pm. If you are interested in astronomy, you are welcome to attend and you do not have to pay any dues to be a member of the club. 

We will discuss the upcoming total eclipse of the moon. The total lunar eclipse will be visible (weather permitting) on December 20/21. Totality will begin at 11:41 p.m., peak at 12:17a.m, and end at 12:53a.m.

The moon will start off being in full phase. At 10:32p.m, it will enter the umbral shadow of the Earth and rapidly go through its phases (waning gibbous, third quarter, waning crescent) in a short span until totality begins at 11:41p.m., when it will be in new moon phase.

Then for about 72 minutes, the moon will appear dark and reddened. From the time totality ends at 12:53a.m, the moon will rapidly go through its phases in reverse order (waxing crescent, first quarter, waxing gibbous) in a short span as it leaves Earth's umbral shadow, until it is full again at 2:02a.m.

Eclipses occur when the Earth, moon, and sun line up in straight line while each is moving in its own orbit. When Earth happens to be in the middle, we observe a lunar eclipse, and when the moon is in the middle we have a solar eclipse.

Lunar eclipses occur on or very close to the full moon phase. At this time the moon is on the opposite side of the Earth from the sun. The moon is darkened as all (total eclipse) or some (partial eclipse) of the sun's light is blocked by the Earth. Because the Earth is much bigger than the moon, its shadow cone encompasses the moon. Lunar eclipses are thus visible from all the night half of the Earth.

Solar eclipses occur on or close to the new moon phase when the moon is between the Earth and the sun. Even though the moon is much smaller than the sun, it appears the same size in the sky because of its close proximity to the Earth. Because of this incredible co-incidence, the moon obscures the sun either completely (total eclipse), partly (partial eclipse), or nearly (annular or ring eclipse). As the shadow cone of the moon is relatively small, only a small area on the Earth's surface witnesses a solar eclipse.

Eclipses do not happen on every new and full moon. This is because the orbit of the moon is inclined by 5 degrees from the orbital plane of the Earth. Most of the time, the moon is either above or below this plane and hence the Earth, moon, and sun do not line up.

At the two points called nodes where the Earth's and the moon's orbital planes intersect, we can get eclipses. Generally, in a year there are 2 eclipse seasons six months apart, each with a possibility of one solar eclipse and one lunar eclipse.

As the moon is slowly moving away from Earth, there will come a time when the observers on Earth will not be able to witness eclipses.

Telescope viewing will be available after the presentation, weather permitting.

Explorit’s coming events:

Dec. 18 – Jan. 2: Both floors of the museum will be open for special hours Dec. 18 – Jan. 2 (except for the holidays on Dec. 25 and Jan. 1.  Click here for the daily hours.

Through Dec. 31: Make The Explorit Store your stop for holiday gifts for the whole family. Shoppers do not need to pay admission to shop in The Store.  Store hours are the same as museum hours (below). Visit to see the new items.

Explorit Science Center, at 2801 Second St., has two exhibitions on display: “Move It! Science in Action” and “Wheels to Wings.”  Admission is $4 general, free for teachers, and ages 3 and under.  The museum is open to school groups by reservation and to the general public 10 a.m. to 5 p.m.  Tuesdays and 11 a.m. to 5:00 p.m. Saturday and Sunday.  For more information call (530) 756-0191 or visit

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