Lunar eclipse

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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.

File:Lunareclipsediagram1.gif

Contents

Types of lunar eclipses

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 eclipse.

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 totality may last up to nearly 107 minutes. However, the time between the Moon's first contact with the shadow and last contact, when it has completely exited the shadow, may be up to 6 h 14 min or so. 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 André 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.

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.

File: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] [2] 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 (time data in UTC):

Date Begin of penumbral eclipse Begin of partial eclipse Begin of totality Maximum/Type End of totality End of partial eclipse End of penumbral eclipse Size
May 4 2004 18:51 19:48 20:52 21:30/total 22:08 23:12 00:09 1.309
October 28 2004 01:06 02:14 03:23 04:04/total 04:44 05:53 07:03 1.314
April 24 2005 07:50 - - 09:55/penumbral-partial - - 12:00 0.890
October 17 2005 09:51 11:34 - 12:03/partial - 12:32 14:15 0.069
March 14 2006 21:21 - - 23:47/penumbral-total - - 01:13 1.056
September 7 2006 17:42 19:05 - 19:51/partial - 20:37 22:00 0.189
March 3 2007 20:16 21:30 22:43 23:20/total 23:57 01:11 02:25 1.237
August 28 2007 07:52 08:51 09:52 10:37/total 11:23 12:24 13:22 1.481
February 21 2008 00:35 01:42 03:00 03:26/total 03:51 05:09 06:17 1.112
August 16 2008 19:23 20:35 - 22:10/partial - 23:44 00:57 0.812
February 9 2009 12:37 - - 14:38/penumbral-partial - - 16:40 0.925
July 7 2009 08:33 - - 09:39/penumbral-partial - - 10:44 0,182
August 6 2009 00:01 - - 01:39/penumbral-partial - - 03:17 0.428
December 31 2009 17:15 18:51 - 19:22/partial - 19:53 21:30 0.081
June 26 2010 08:55 10:16 - 11:38/partial - 13:00 14:21 0.543
December 21 2010 05:28 06:32 07:40 08:17/total 08:54 10:02 11:06 1.261
June 15 2011 17:23 18:23 19:22 20:13/total 21:03 22:02 23:02 1.706
December 10 2011 11:32 12:45 14:06 14:32/total 14:58 16:18 17:32 1.110
June 4 2012 08:46 09:59 - 11:03/partial - 12:07 13:20 1.377
November 28 2012 12:13 - - 14:33/partial-penumbral - - 16:53 0.942
April 25 2013 18:02 19:52 - 20:07/partial - 20:23 22:13 0.019
May 25 2013 03:43 - - 04:10/partial-penumbral - - 04:37 0.04
October 18 2013 21:48 - - 23:50/partial-penumbral - - 01:52 0.792
April 15 2014 04:52 05:58 07:07 07:46/total 08:25 09:34 10:39 1.295
October 8 2014 08:14 09:15 10:25 10:55/total 11:25 12:35 13:35 1.172
April 4 2015 09:00 10:16 11:54 12:00/total 12:06 13:45 15:01 1.005
September 28 2015 00:10 01:07 02:11 02:47/total 03:24 04:28 05:24 1.282
March 23 2016 09:37 - - 11:47/penumbral-partial - - 13:58 0.801
August 18 2016 09:25 - - 09:43/penumbral-partial - - 10:01 0.015
September 16 2016 16:53 - - 18:54/penumbral-partial - - 20:56 0.933
February 11 2017 22:32 - - 00:44/penumbral-total - - 02:56 1.015
August 7 2017 15:48 17:22 - 18:21/partial - 19:19 20:53 0.250
January 31 2018 10:50 11:48 12:52 13:30/total 14:08 15:12 16:10 1.321
July 27 2018 17:13 18:24 19:30 20:22/total 21:14 22:20 23:31 1.613
January 21 2019 02:35 03:34 04:41 05:12/total 05:44 06:51 07:50 1.201
July 16 2019 18:42 20:01 - 21:31/partial - 23:00 00:20 0.659
July 16 2019 18:42 20:01 - 21:31/partial - 23:00 00:20 0.659
January 10 2020 17:06 - - 19:10/penumbral-partial - - 21:15 0.920
June 5 2020 17:44 - - 19:25/penumbral-partial - - 21:07 0.594
July 5 2020 03:04 - - 04:30/penumbral-partial - - 05:56 0.381
November 30 2020 07:30 - - 09:43/penumbral-partial - - 11:56 0.854

Longest total lunar eclipse between 1900 and 2100

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

The longest total lunar eclipse between 1000BC and 3000AD took place on May 31 318. 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

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