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Lunar eclipse

From Academic Kids

An eclipse occurs whenever the Sun, Earth and Moon line up exactly. If this occurrence is at the time of a full moon where the Moon passes through the Earth's shadow, it is called a lunar eclipse. The type and length of a lunar eclipse depends upon the Moon's location relative to its orbital node.

Image:Lunareclipsediagram1.gif

Contents

Types of lunar eclipses

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Lunareclipsediagram3.gif
Descending node lunar eclipse paths

A penumbral eclipse occurs when the Moon only passes through the Earth's penumbra, the outer portion of the Earth's shadow. The penumbra does not cause a noticeable darkening of the Moon's surface.

A special type of penumbral eclipse is a total penumbral eclipse. At a total penumbral eclipse the moon is completely in the penumbra of the earth, but not in the umbra. At a total penumbral eclipse the parts of the moon closest to the umbra are a bit darker than the rest of the moon. Total penumbral eclipses are a rare type of lunar eclipses.

A total lunar eclipse occurs when the Moon travels completely into the Earth's umbra, the dark inner portion of the shadow. The Moon's speed through the shadow is about one kilometer per second, and the total eclipse may last up to 102 minutes. However, the time between the Moon's first contact with the umbra and last contact, when it has completely exited the umbra, may be several hours. If only part of the Moon enters the umbra, it is called a partial lunar eclipse.

The Moon doesn't completely disappear as it passes through the umbra because of the refraction of sunlight by the Earth's atmosphere. The amount of refracted light depends on the amount of clouds or dust in the atmosphere blocking the light. This causes the Moon to glow with a coppery-red hue that varies from one eclipse to the next. The following scale was devised by Andr Danjon for rating the overall darkness of lunar eclipses:

0. Very dark eclipse; Moon almost invisible, especially in midtonality
1. Dark eclipse; gray or brownish coloration; details distinguishable only with difficulty
2. Deep red or rust-colored eclipse, with a very dark central part in the umbra and the outer rim of the umbra relatively bright
3. Brick-red eclipse, usually with a bright or yellow rim to the umbra
4. Very bright copper-red or orange eclipse, with a bluish, very bright umbral rim

Because the Moon's orbit around the Earth is inclined 5° with respect to the orbit of the Earth around the Sun, lunar eclipses do not occur at every full moon. For an eclipse to occur, the Moon must be near its orbital node—the intersection of the orbital planes. Passing through the shadow at or very close to the node results in a total or partial eclipse.

The relative distance of the Moon from the Earth at the time of the eclipse can affect the eclipse's intensity. Specifically, a totally-eclipsed Moon being concomitantly at or near apogee will lengthen the duration of totality for two reasons: First, the Moon will appear to move more slowly across the umbra, and second, the Moon will appear smaller as seen from Earth and therefore remain inside the umbra longer.

Missing image
Lunareclipsediagram2.gif
Lunar nodes

Every year there are at least two lunar eclipses. If you know the date and time of an eclipse, you can predict the occurrence of other eclipses using eclipse cycles. Unlike a solar eclipse, which can only be viewed in a certain relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of the Earth. If you were on the Moon's surface during a lunar eclipse you would witness a solar eclipse, with the Earth passing in front of the Sun.

Missing image
Lunareclipses2003.jpg

Lunar eclipses in 2003

Two total lunar eclipses occurred in 2003. The eclipse on May 15 grazed the northern edge of the earth's shadow, and the eclipse on November 8 grazed the southern edge. These images show the eclipse in November was much brighter as the bottom rim of the Moon did not darken as much after completely entering the umbra. The color and brightness of the Moon during an eclipse varies according to the amount of light refracted by the Earth's atmosphere.

Lunar eclipse predictions 2005-2006

Predictions by [1] (http://sunearth.gsfc.nasa.gov/eclipse/LEcat/LE2001-2100.html) [2] (http://sunearth.gsfc.nasa.gov/eclipse/OH/OH2005.html) Fred Espenak, NASA
Date Time (UT) of Greatest Eclipse Type Visibility Duration of Eclipse
April 24, 2005 09:55 Penumbral Western Hemisphere and Pacific 4 h 10 min
October 17, 2005 12:03 Partial Pacific Rim 58 min (partial phase)
March 14, 2006 23:48 Penumbral Europe, Africa (Unavailable from source)
September 7, 2006 18:51 Partial Asia 1 h 32 min (partial phase)

Lunar eclipses, visible in Europe (time data in UTC + 1hour:

Datum Begin of penumbral eclipse Begin of partial eclipse Begin of totality Maximum/Type End of totality End of partial eclipse End of penumbral eclipse Gre
4. Mai 2004 19:51 20:48 21:52 22:30/total 23:08 00:12 01:09 1,309
28. Oktober 2004 02:06 03:14 04:23 05:04/total 05:44 06:53 08:03 1,314
14. Mrz 2006 22:21 - - 0:47/penumbral-total - - 02:13 1,056
7. September 2006 18:42 20:05 - 20:51/partiell - 21:37 23:00 0,189
3. Mrz 2007 21:16 22:30 23:43 00:20/total 00:57 02:11 03:25 1,237
21. Februar 2008 01:35 02:42 04:00 04:26/total 04:51 06:09 07:17 1,112
16. August 2008 20:23 21:35 - 23:10/partiell - 00:44 01:57 0,812
6. August 2009 01:01 - - 02:39/penumbral-partiell - - 04:17 0,428
31. Dezember 2009 18:15 19:51 - 20:22/partiell - 20:53 22:30 0,081


Longest total lunar eclipse between 1900 and 2100

Date Duration of total phase
July 16th, 2000 1h47m01s
July 6th, 1982 1h46m20s
July 27th, 2018 1h43m34s
June 26th, 2029 1h42m32s
August 4th, 1906 1h41m48s
July 7th, 2047 1h41m29s
June 25th, 1964 1h41m25s
July 26th, 1953 1h41m22s
June 28th, 2001 1h41m16s
June 15th, 2011 1h40m52s
June 16th, 2076 1h40m49s
July 15th, 1935 1h40m16s
August 6th, 1971 1h40m04s

The longest total lunar eclipse between 1000BC and 3000AD took place on May 31st, 318. Its total phase had a duration of 1h47m14s.

History

Ancient Greek astronomers noticed that during lunar eclipses the edge of the shadow was always circular; they thus concluded that the Earth was spherical. In 1504, while stranded on Jamaica, Christopher Columbus predicted a lunar eclipse, thereby intimidating the island's natives into continuing to provision him and his men and thus saving them from death by starvation.

References

  • Alan MacRobert, "October's Ideal Lunar Eclipse", Sky and Telescope (October 2004), p. 74. (Danjon numbers)

See also

External links

Prediction
Eclipse photos
Fiction

de:Mondfinsternis es:Eclipse lunar nl:Maansverduistering he:ליקוי_ירח ja:月食 pl:Zaćmienie Księżyca sl:Lunin mrk sv:Mnfrmrkelse fi:Kuunpimennys zh:月食

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