Lunar eclipse
Overview
 
A lunar eclipse occurs when the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 passes behind the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 so that the Earth blocks the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

's rays from striking the Moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a full moon
Full moon
Full moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...

. The type and length of an eclipse depend upon the Moon's location relative to its orbital node
Lunar node
The lunar nodes are the orbital nodes of the Moon, that is, the points where the orbit of the Moon crosses the ecliptic . The ascending node is where the moon crosses to the north of the ecliptic...

s. The most recent total lunar eclipse
June 2011 lunar eclipse
A total lunar eclipse took place on June 15, 2011. It was the first of two such eclipses in 2011. The second will occur on December 10, 2011.This was a relatively rare central lunar eclipse, in which the center point of Earth's shadow passes across the Moon. The last time a lunar eclipse was closer...

 occurred on June 15, 2011; it was a central eclipse, visible over Europe and South America after sunset, over Africa and most of Asia, and Australia before sunrise.
Encyclopedia
A lunar eclipse occurs when the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 passes behind the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 so that the Earth blocks the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

's rays from striking the Moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a full moon
Full moon
Full moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...

. The type and length of an eclipse depend upon the Moon's location relative to its orbital node
Lunar node
The lunar nodes are the orbital nodes of the Moon, that is, the points where the orbit of the Moon crosses the ecliptic . The ascending node is where the moon crosses to the north of the ecliptic...

s. The most recent total lunar eclipse
June 2011 lunar eclipse
A total lunar eclipse took place on June 15, 2011. It was the first of two such eclipses in 2011. The second will occur on December 10, 2011.This was a relatively rare central lunar eclipse, in which the center point of Earth's shadow passes across the Moon. The last time a lunar eclipse was closer...

 occurred on June 15, 2011; it was a central eclipse, visible over Europe and South America after sunset, over Africa and most of Asia, and Australia before sunrise. It lasted 100 minutes. The previous total lunar eclipse occurred on December 21, 2010, at 08:17 UTC.

Unlike a solar eclipse
Solar eclipse
As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially blocks the Sun as viewed from a location on Earth. This can happen only during a new moon, when the Sun and the Moon are in conjunction as seen from Earth. At least...

, 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.

Types of lunar eclipse


The shadow of the Earth can be divided into two distinctive parts: the umbra
Umbra
The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow, created by any light source. For a point source only the umbra is cast.These names are most often used to refer to the shadows cast by celestial bodies....

 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.
A 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.
A 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:
P1 (First contact): Beginning of the penumbral eclipse. The Earth's penumbra touches the Moon's outer limb.
U1 (Second contact): Beginning of the partial eclipse. The Earth's umbra touches the Moon's outer limb.
U2 (Third contact): Beginning of the total eclipse. The Moon's surface is entirely within the Earth's umbra.
Greatest eclipse: The peak stage of the total eclipse. The Moon is at its closest to the center of the Earth's umbra.
U3 (Fourth contact): End of the total eclipse. The Moon's outer limb exits the Earth's umbra.
U4 (Fifth contact): End of the partial eclipse. The Earth's umbra leaves the Moon's surface.
P2 (Sixth contact): End of the penumbral eclipse. The Earth's shadow
Earth's shadow
The Earth's shadow or Earth shadow are names for the shadow that the Earth itself casts on its atmosphere. This shadow is often visible from the surface of the Earth, as a dark band in the sky near the horizon...

 no longer makes any contact with the Moon.


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. It happens during every lunar eclipse at all those places on the Earth where it is sunrise or sunset at the time. 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 geometrical shadow, the Sun and the eclipsed Moon can appear in the sky at the same time because the refraction
Refraction
Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...

 of light through the Earth’s atmosphere causes objects near the horizon
Horizon
The horizon is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not. At many locations, the true horizon is obscured by trees, buildings, mountains, etc., and the resulting...

 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
Refraction
Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...

 of sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...

 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
Rayleigh scattering
Rayleigh scattering, named after the British physicist Lord Rayleigh, is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light. The particles may be individual atoms or molecules. It can occur when light travels through...

. Shorter wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

s 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
Red
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...

. This is the same effect that causes sunset
Sunset
Sunset or sundown is the daily disappearance of the Sun below the horizon in the west as a result of Earth's rotation.The time of sunset is defined in astronomy as the moment the trailing edge of the Sun's disk disappears below the horizon in the west...

s and sunrise
Sunrise
Sunrise is the instant at which the upper edge of the Sun appears above the horizon in the east. Sunrise should not be confused with dawn, which is the point at which the sky begins to lighten, some time before the sun itself appears, ending twilight...

s 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.

Danjon scale

The following scale (the Danjon scale
Danjon scale
The Danjon Scale of lunar eclipse brightness is a five-point scale useful for measuring the appearance and luminosity of the Moon during a lunar eclipse. It was proposed by André-Louis Danjon when he was measuring the Earthshine on the Moon...

) was devised by André Danjon
André Danjon
André-Louis Danjon was a French astronomer born in Caen.Danjon devised a method to measure "Earthshine" on the Moon using a telescope in which a prism split the Moon's image into two identical side-by-side images...

 for rating the overall darkness of lunar eclipses:
L=0: Very dark eclipse. Moon almost invisible, especially at mid-totality.
L=1: Dark eclipse, gray or brownish in coloration. Details distinguishable only with difficulty.
L=2: Deep red or rust-colored eclipse. Very dark central shadow, while outer edge of umbra is relatively bright.
L=3: Brick-red eclipse. Umbral shadow usually has a bright or yellow rim.
L=4: Very bright copper-red or orange eclipse. Umbral shadow is bluish and has a very bright rim.

Eclipse cycles

Every year there are at least two lunar eclipses, although total lunar eclipses are significantly less common. If one knows the date and time of an eclipse, it is possible to predict the occurrence of other eclipses using an eclipse cycle
Eclipse cycle
Eclipses may occur repeatedly, separated by certain intervals of time: these intervals are called eclipse cycles. The series of eclipses separated by a repeat of one of these intervals is called an eclipse series.- Eclipse conditions :...

 like the saros.

Recent and forthcoming lunar eclipse events

  • March 3, 2007, lunar eclipse
    March 2007 lunar eclipse
    A total lunar eclipse took place on March 3, 2007, the first of two eclipses in 2007. The moon entered the penumbral shadow at 20:18 UTC, and the umbral shadow at 21:30 UTC. The total phase lasted between 22:44 UTC and 23:58 UTC with a distinctive brick-red shade...

     ― The first total lunar eclipse of 2007 occurred on March 3, 2007, and was partially visible from the Americas
    Americas
    The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

    , Asia
    Asia
    Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

     and Australia
    Australia
    Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

    . The complete event was visible throughout Africa
    Africa
    Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

     and Europe
    Europe
    Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

    . The event lasted seventy-five minutes, began at 20:16 UTC
    Universal Time
    Universal Time is a time scale based on the rotation of the Earth. It is a modern continuation of Greenwich Mean Time , i.e., the mean solar time on the Prime Meridian at Greenwich, and GMT is sometimes used loosely as a synonym for UTC...

    , and reached totality at 22:43 UTC.
  • August 2007 lunar eclipse
    August 2007 lunar eclipse
    A total lunar eclipse occurred on August 28, 2007, lasting just over 90 minutes. The Moon entered the Earth's penumbra at 07:53:39 UTC. The first partial phase began in earnest at 08:51:16 UTC when the Moon entered the Earth's umbra. It exited the penumbra at 13:21:02 UTC.It is a relatively rare...

     ― August 28, 2007, saw the second total lunar eclipse of the year. The initial stage began at 07:52 UTC
    Universal Time
    Universal Time is a time scale based on the rotation of the Earth. It is a modern continuation of Greenwich Mean Time , i.e., the mean solar time on the Prime Meridian at Greenwich, and GMT is sometimes used loosely as a synonym for UTC...

    , and reached totality at 09:52 UTC. This eclipse was viewable form Eastern Asia, Australia and New Zealand
    New Zealand
    New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

     the Pacific, and the Americas.
  • February 2008 lunar eclipse
    February 2008 lunar eclipse
    A total lunar eclipse occurred on the evening of Wednesday, February 20, and morning of Thursday, February 21, 2008. It was visible in the eastern evening sky on February 20 for all of North and South America, and on February 21 in the predawn western sky from most of Africa and Europe.The total...

     ― The only total lunar eclipse of 2008 occurred on February 21, 2008, beginning at 01:43 UTC, visible from Europe, the Americas, and Africa.
  • There was a partial eclipse of the Moon on December 31, 2009
    December 2009 lunar eclipse
    A partial lunar eclipse was visible on New Year's Eve, December 31, 2009. It was the last and largest of four minor lunar eclipses in 2009. This lunar eclipse is also notable, because it occurred during a blue moon...

    .
  • There was a partial eclipse of the Moon on June 26, 2010
    June 2010 lunar eclipse
    The partial lunar eclipse of June 26, 2010 was the first of two lunar eclipses in 2010. At maximum eclipse 53.7% of the moon was covered by the earth's shadow.This eclipse preceded by two weeks the total Solar eclipse of July 11, 2010 over the South Pacific....

    .
  • There was a total eclipse of the Moon on December 21, 2010
    December 2010 lunar eclipse
    The December 2010 lunar eclipse occurred from 5:27 to 11:06 UTC on December 21, coinciding with the date of the December solstice. It was visible in its entirety as a total lunar eclipse in North and South America, Iceland, Ireland, Britain and northern Scandinavia.-Occurrence:The eclipse of...

    .
  • There was a total eclipse of the Moon on June 15, 2011
    June 2011 lunar eclipse
    A total lunar eclipse took place on June 15, 2011. It was the first of two such eclipses in 2011. The second will occur on December 10, 2011.This was a relatively rare central lunar eclipse, in which the center point of Earth's shadow passes across the Moon. The last time a lunar eclipse was closer...

    .
  • The next total eclipse of the Moon will occur on December 10, 2011
    December 2011 lunar eclipse
    A total lunar eclipse will take place on December 10, 2011. It will be the second of two total lunar eclipses in 2011, the first having occurred on June 15.- Visibility :...

    .

See also

  • Lunar eclipses in history
    • May 1453 lunar eclipse
      May 1453 lunar eclipse
      A partial lunar eclipse occurred on May 22, 1453.-Observations:It was seen during the Fall of Constantinople , during the siege that lasted from Thursday, 5 April 1453 until Tuesday, 29 May 1453), after which the city fell to the Ottomans. The lunar eclipse was considered to be fulfilling a...

       - Fall of Constantinople
      Fall of Constantinople
      The Fall of Constantinople was the capture of the capital of the Byzantine Empire, which occurred after a siege by the Ottoman Empire, under the command of Ottoman Sultan Mehmed II, against the defending army commanded by Byzantine Emperor Constantine XI...

    • March 1504 lunar eclipse
      March 1504 lunar eclipse
      A total lunar eclipse occurred on March 1, 1504 .Christopher Columbus, in a desperate effort to induce the natives of Jamaica to continue provisioning him and his hungry men, successfully intimidated the natives by correctly predicting a lunar eclipse for February 29, 1504, using the Ephemeris of...

       - Columbus’ lunar eclipse
    • December 1573 lunar eclipse
      December 1573 lunar eclipse
      A total lunar eclipse occurred on December 8, 1573.It was predicted and then observed by a young Tycho Brahe at Knutstorp Castle. He said "I cannot but be very surprised that even at this youthful age of 26 years, I was able to get such accurate results."- External links:* Tycho observes a lunar...

       - Tycho Brahe
      Tycho Brahe
      Tycho Brahe , born Tyge Ottesen Brahe, was a Danish nobleman known for his accurate and comprehensive astronomical and planetary observations...

  • Eclipse
    Eclipse
    An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer...

  • Moon illusion
    Moon illusion
    The Moon illusion is an optical illusion in which the Moon appears larger near the horizon than it does while higher up in the sky. This optical illusion also occurs with the sun and star constellations. It has been known since ancient times, and recorded by numerous different cultures...

  • Orbit of the Moon

External links

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