Handouts(Lunar Eclipse)

Lunar Eclipse
By:
Melejoy P. Tedria BEEd 2B

Partido State University

Goa, Camarines Sur

College of Education

A\Y 2012-2013

mjyedria@yahoo.com
smilguyz.blogspot.com

                    A lunar eclipse occurs whenever the moon passes through some portions of the Earth’s shadow. This can only happen when the sun, earth, and moon are aligned, with earth in the middle.

During a lunar eclipse, the moon turns dark. The Earth’s shadow falls on the moon. When the moon moves through the Earth’s shadow or umbra, a total lunar eclipse occurs. When the moon moves through the earth’s penumbra, a partial lunar eclipse occurs.

Reference: Science for Daily Use IV—Grade 4

              Lunar eclipse occurs when the moon passes directly behind the earth into its umbra  (shadow). This can occur only when the Sun, Earth, and Moon are aligned (in "syzygy") exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a full moon. The type and length of an eclipse depend upon the Moon's location relative to its orbital nodes. Unlike a solar eclipse, which can only be viewed from a certain relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of the Earth. A lunar eclipse lasts for a few hours, whereas a total solar eclipse lasts for only a few minutes at any given place, due to the smaller size of the moon's shadow. Also unlike solar eclipses, lunar eclipses are safe to view without any eye protection or special precautions, as they are no brighter (indeed dimmer) than the full moon itself.

                 Types of Lunar Eclipse

                 The shadow of the Earth can be divided into two distinctive parts: the umbra and penumbra. Within the umbra, there is no direct solar radiation. However, as a result of the Sun’s large angular size, solar illumination is only partially blocked in the outer portion of the Earth’s shadow, which is given the name penumbra.

• Penumbral eclipse 

                    Occurs when the Moon passes through the Earth’s penumbra. The penumbra causes a subtle darkening of the Moon's surface. A special type of penumbral eclipse is a total penumbral eclipse, during which the Moon lies exclusively within the Earth’s penumbra

• Total penumbral eclipses

                           Are rare, and when these occur, that portion of the Moon which is closest to the umbra can appear somewhat darker than the rest of the Moon.

•    Partial lunar eclipse 

                 Occurs when only a portion of the Moon enters the umbra. When the Moon travels completely into the Earth’s umbra, one observes a total lunar eclipse. The Moon’s speed through the shadow is about one kilometer per second (2,300 mph), and totality may last up to nearly 107 minutes. Nevertheless, the total time between the Moon’s first and last contact with the shadow is much longer, and could last up to 4 hours. The relative distance of the Moon from the Earth at the time of an eclipse can affect the eclipse’s duration. In particular, when the Moon is near its apogee, the farthest point from the Earth in its orbit, its orbital speed is the slowest. The diameter of the umbra does not decrease appreciably within the changes in the orbital distance of the moon. Thus, a totally eclipsed Moon occurring near apogee will lengthen the duration of totality.

The timing of total lunar eclipses are determined by its contacts:

1.            P1 (First contact):    Beginning of the penumbral eclipse. The Earth's penumbra touches the Moon's outer limb.
2.            U1 (Second contact):   Beginning of the partial eclipse. The Earth's umbra touches the Moon's outer limb.
3.             U2 (Third contact):   Beginning of the total eclipse. The Moon's surface is entirely within the Earth's umbra.
4.             Greatest eclipse:   The peak stage of the total eclipse. The Moon is at its closest to the center of the Earth's umbra.
5.              U3 (Fourth contact):  End of the total eclipse. The Moon's outer limb exits the Earth's umbra.
6.       U4 (Fifth contact):   End of the partial eclipse. The Earth's umbra leaves the Moon's surface.
7.            P2 (Sixth contact):  End of the penumbral eclipse. The Earth's shadow no longer makes any contact with the Moon.

 Selenelion

             A selenelion or selenehelion occurs when both the Sun and the eclipsed Moon can be observed at the same time. This can only happen just before sunset or just after sunrise, and both bodies will appear just above the horizon at nearly opposite points in the sky. This arrangement has led to the phenomenon being referred to as a horizontal eclipse. There are typically a number of high ridges undergoing sunrise or sunset that can see it. Indeed, the reddened light that reaches the Moon comes from all the simultaneous sunrises and sunsets on the Earth. Although the Moon is in the Earth’s umbra, the Sun and the eclipsed Moon can both be seen at the same time because the refraction of light through the Earth’s atmosphere causes each of them to appear higher in the sky than their true geometric position.

•         The Moon does not completely disappear as it passes through the umbra because of the refraction of sunlight by the Earth’s atmosphere into the shadow cone; if the Earth had no atmosphere, the Moon would be completely dark during an eclipse. The red coloring arises because sunlight reaching the Moon must pass through a long and dense layer of the Earth’s atmosphere, where it is scattered. Shorter wavelengths are more likely to be scattered by the air molecules and the small particles, and so by the time the light has passed through the atmosphere, the longer wavelengths dominate. This resulting light we perceive as red. This is the same effect that causes sunsets and sunrises to turn the sky a reddish color; an alternative way of considering the problem is to realize that, as viewed from the Moon, the Sun would appear to be setting (or rising) behind the Earth.
•            The amount of refracted light depends on the amount of dust or clouds in the atmosphere; this also controls how much light is scattered. In general, the dustier the atmosphere, the more that other wavelengths of light will be removed (compared to red light), leaving the resulting light a deeper red color. This causes the resulting coppery-red hue of the Moon to vary from one eclipse to the next. Volcanoes are notable for expelling large quantities of dust into the atmosphere, and a large eruption shortly before an eclipse can have a large effect on the resulting color.

Reference: http://en.wikipedia.org/wiki/Lunar_eclipse

                                     The Comparison of Lunar to Solar Eclipse

Lunar Eclipse Compared To Solar Eclipse

            A "lunar eclipse" and a "solar eclipse" refer to events involving three celestial bodies: the Sun ("solar"), the moon ("lunar"), and the Earth.

• A lunar eclipse occurs when the Earth passes between the Moon and the Sun, and the Earth's shadow obscures the moon or a portion of it.
• A solar eclipse occurs when the Moon passes between the Earth and the Sun, blocking all or a portion of the Sun. 

                An eclipse can be total, partial, or annular. A total solar eclipse is when the moon blocks out the Sun entirely, a partial eclipse is when it blocks out a portion of the Sun, and an annular eclipse is when the moon is at its furthest point in orbit. It will not cover the Sun completely that's when you can see a thin ring of light emerging from the outside rim of the moon. 

How are a lunar eclipse and solar eclipse different? 

             A lunar eclipse occurs at night and a solar eclipse occurs during the day. There are only certain times when either of them can occur. A lunar eclipse can only occur when the moon is directly opposite the Sun in the sky — a full moon. Even though there is a full moon each month, obviously a lunar eclipse does not occur on a monthly basis because the Sun isn't exactly in line with the Earth and the moon. The moon's orbit is actually tilted 5 degrees more than that of the Earth; otherwise, we would see a lunar eclipse each month. 

•              We can see lunar eclipses more readily than solar eclipses, and it has to do with proximity. The Moon is much closer to the Earth (well over 300 times closer than the Sun!), so the Earth has a much greater chance of blocking sunlight to the Moon, compared to the Moon blocking light from the Sun. Also, a lunar eclipse can be seen from a greater portion of the Earth. Solar eclipses, on the other hand, are more rare and when they do happen can only be seen by a very narrow segment of people on Earth, for a short period of time. 

•          It is quite safe to watch a lunar eclipse with the naked eye, while watching a solar eclipse without eye wear protection can seriously damage your eyesight. You can use a telescope to get a clearer view of the moon during an eclipse and really see what is happening. 

           A solar eclipse has always had a more profound effect on humans than a lunar eclipse. This is probably because of the importance of the Sun to all life on Earth. In ancient China, a solar eclipse was thought to be the dragon coming to eat the Sun. The effect that an eclipse has on all life on Earth is of particular interest to scientists. They eagerly await a solar eclipse because it helps them to gather more knowledge about the Sun and its position with respect to Earth.

Reference: http://www.moonconnection.com/lunar_vs_solar.phtml

 Duration of Lunar Eclipses

•            During an average total lunar eclipse, the moon is within the Earth's umbra for about an hour. This is called totality. 

Frequency of Lunar Eclipses

•          Since the plane of the moon's orbit is inclined about 5°: from the plane of the Earth's orbit, lunar eclipses are relatively infrequent. There are about two lunar eclipses each year (visible somewhere on Earth).

Reference: http://www.enchantedlearning.com/subjects/astronomy/moon/Lunareclipse.shtml

                       The Position of the Lunar Eclipse

   

Reference: http://www.mreclipse.com/Special/image/LEDiagram1c.JPG

Reference: http://static.ddmcdn.com/gif/lunar-ecl

Watching Beauty In Action

•          Seeing a lunar eclipse depends on your location. When it is very visible in one part of the world, it can't be see in other parts. Only where it is night can you see the wonderful display of the eclipse. Such a phenomenon is very safe to watch. It is not even necessary to use a telescope and when you watch what a treat you are in for! The colors range from deep browns, very dark grays, various shades of brilliant reds and many shades of bright oranges. As the moon passes, these colors vary depending on the amount of dust in the Earth's atmosphere. If you are lucky enough to witness this spectacular show of beauty, the chances of seeing the same thing twice is pretty remote.

      

Reference: http://askville.amazon.com/precautions-watching-lunar-eclipse/AnswerViewer.do?requestId=35439787

Cause of Lunar Eclipse

             What are the causes of lunar eclipses? 

•       On the night of a lunar eclipse, the Earth, the Sun and the Moon are positioned in one straight line, with the Earth lying in between the Sun and the Moon. With this placement of the three celestial bodies, the Earth casts a shadow on the surface of the Moon. To put it simply, the Moon travels through some portion of the Earth's shadow, causing a lunar eclipse.

Reference: http://www.buzzle.com/articles/causes-of-lunar-eclipses.html

       Quotes about Lunar Eclipse

"The Sun was eclipsed, a thing of very evil omen. Then the Moon became small, and now the Sun became small. . . . For the Moon to be eclipsed is but an ordinary matter. Now that the Sun has been eclipsed - how bad it is!"
Date: February 14,2013

Reference: http://www.mreclipse.com/Special/quotes.html

                 Refers to successive eclipses (one lunar, one solar) in the 8th century BC. The solar eclipse is said to have occurred on the day hsin-mao, which was the first day of the 10th lunar month. This may have been in 735 BC.

From: the Shih-ching ("Book of Odes") (China, 8th century BC).
Quoted in Encyclopaedia Britannica CD 98, and in Historical Eclipses and Earth's Rotation, by F Richard Stephenson, Cambridge University Press, 1997, page 222.