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Schematic diagram of the shadow cast by the Earth. Within the central umbra shadow, the Moon is totally shielded from direct illumination by the Sun. In contrast, within the penumbra shadow, only a portion of the sunlight is blocked.
Schematic diagram of the shadow cast by the Earth. Within the central umbra shadow, the Moon is totally shielded from direct illumination by the Sun. For other uses of the word "umbra" see Umbra (disambiguation. In contrast, within the penumbra shadow, only a portion of the sunlight is blocked. For other uses of the word "umbra" see Umbra (disambiguation.
As seen by an observer on Earth on the imaginary celestial sphere, the Moon crosses the ecliptic every orbit at positions called nodes twice every month. When the full moon occurs in the same position at the node, a lunar eclipse can occur. These two nodes allow two to five eclipses per year, parted by approximately six months. (Note: Not drawn to scale. The Sun is much larger and farther away than the Moon.)
As seen by an observer on Earth on the imaginary celestial sphere, the Moon crosses the ecliptic every orbit at positions called nodes twice every month. In Astronomy and Navigation, the celestial sphere is an imaginary rotating Sphere of "gigantic Radius " When the full moon occurs in the same position at the node, a lunar eclipse can occur. These two nodes allow two to five eclipses per year, parted by approximately six months. (Note: Not drawn to scale. The Sun is much larger and farther away than the Moon. )
As viewed from Earth, the Earth's shadow can be imagined as two concentric circles. As the diagram illustrates, the type of lunar eclipse is defined by the path taken by the Moon as it passes through Earth's shadow. If the Moon passes through the outer circle but does not reach the inner circle, it is a penumbral eclipse; if only a portion of the Moon passes through the inner circle, it is a partial eclipse; and if entire Moon passes through the inner circle at some point, it is a total eclipse.
As viewed from Earth, the Earth's shadow can be imagined as two concentric circles. As the diagram illustrates, the type of lunar eclipse is defined by the path taken by the Moon as it passes through Earth's shadow. If the Moon passes through the outer circle but does not reach the inner circle, it is a penumbral eclipse; if only a portion of the Moon passes through the inner circle, it is a partial eclipse; and if entire Moon passes through the inner circle at some point, it is a total eclipse.

A lunar eclipse occurs whenever the Moon passes through some portion of the Earth's shadow. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. The Sun (Sol is the Star at the center of the Solar System. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Hence, there is always a full moon the night of a lunar eclipse. Full moon is a Lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. The type and length of an eclipse depend upon the Moon's location relative to its orbital nodes. The lunar nodes are the Orbital nodes of the Moon, that is the points where the orbit of the Moon crosses the Ecliptic (which is the apparent

The most recent lunar eclipse was total, and occurred on February 21, 2008. A total Lunar eclipse occurred on the evening of Wednesday February 20, and morning of Thursday February 21, 2008. The next eclipse--a partial one--occurs on August 16, 2008. The next total lunar eclipse occurs on December 21, 2010. A total lunar eclipse will take place on December 21, 2010, the second of two Lunar eclipses in 2010

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Types of lunar eclipses

The shadow of the Earth can be divided into two distinctive parts: the umbra and penumbra. For other uses of the word "umbra" see Umbra (disambiguation. For other uses of the word "umbra" see Umbra (disambiguation. 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 does not cause any noticeable darkening of the Moon's surface, though some may argue it turns a little yellow. 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 3. 8 hours. [1] 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. In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from The diameter of the umbra does not decrease much with distance. Thus, a totally-eclipsed Moon occurring near apogee will lengthen the duration of totality.

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 of light through the Earth's atmosphere causes objects near the horizon to appear higher in the sky than their true geometric position. Refraction is the change in direction of a Wave due to a change in its Speed. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five The horizon ( Ancient Greek ὁ ὁρίζων, /ho horídzôn/ from ὁρίζειν, "to limit" is the apparent line that separates [2]

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. Refraction is the change in direction of a Wave due to a change in its Speed. Sunlight, in the broad sense is the total spectrum of the Electromagnetic radiation given off by the Sun. The red colouring 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 (named after Lord Rayleigh) is the elastic Scattering of Light or other electromagnetic radiation by particles much smaller Shorter wavelengths are more likely to be scattered by the small particles, and so by the time the light has passed through the atmosphere, the longer wavelengths dominate. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. This resulting light we perceive as 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 This is the same effect that causes sunsets and sunrises to turn the sky a reddish colour; an alternative way of considering the problem is to realise that, as viewed from the Moon, the Sun would appear to be setting (or rising) behind the Earth. Sunset, also called sundown in some American English Dialects is the instant when the trailing edge of the Sun 's disk disappears below Sunrise is the instant at which the upper edge of the Sun appears above the Horizon in the East.

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 colour. 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 colour.

Danjon scale

The following scale (the Danjon scale) was devised by André Danjon for rating the overall darkness of lunar eclipses:[3]

L=0: Very dark eclipse. 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 André-Louis Danjon ( April 6, 1890 &ndash April 21, 1967) was a French Astronomer born in Caen. Moon almost invisible, especially at mid-totality.
L=1: Dark Eclipse, gray or brownish in colouration. 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 has a bluish, very bright rim.

Eclipse cycles

See also: Saros cycle and Eclipse cycle

Every year there are usually at least two partial lunar eclipses, although total eclipses are significantly less common. The Saros cycle is an Eclipse cycle with a period of about 18 years 11 days 8 hours (approximately 6585⅓ days that can be used to predict Eclipses of the Sun may occur repeatedly separated by certain intervals of time these intervals are called eclipse cycles. If one knows the date and time of an eclipse, it is possible to predict the occurrence of other eclipses using an eclipse cycle like the Saros cycle. may occur repeatedly separated by certain intervals of time these intervals are called eclipse cycles. The Saros cycle is an Eclipse cycle with a period of about 18 years 11 days 8 hours (approximately 6585⅓ days that can be used to predict Eclipses of the Sun 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 solar eclipse occurs when the Moon passes between the Sun and the Earth so that the Sun is wholly or partially obscured

Recent lunar eclipse events

The current lunar year eclipse cycle has 8 events, each event separated by 6 lunations (177 days):

Descending node Ascending node
  1. March 14, 2006 - partial
  2. March 3, 2007 - total
  3. February 21, 2008 - total
  4. February 9, 2009 - penumbral
  1. September 7, 2006 - partial
  2. August 28, 2007 - total
  3. August 16, 2008 - partial
  4. August 6, 2009 - penumbral
These charts show the moon's path through the earth's shadow near its ascending and descending nodes. A lunar calendar is a Calendar that is based on cycles of the Moon phase. Lunation is the mean time for one Lunar phase cycle (ie the Synodic period of the Moon) Gallery Relation to other lunar eclipses This eclipse is the first of four Metonic cycle lunar eclipses on the same date March 13-14 each separated Viewing The whole event was visible from Europe, Africa, parts of South America, and some areas of North America, Asia, and A total Lunar eclipse occurred on the evening of Wednesday February 20, and morning of Thursday February 21, 2008. Visibility The eclipse will not be visible in the East coast of the United States South America and southernmost Mexico Western Africa and western Europe A partial Lunar eclipse took place on September 7 2006 the second of two lunar eclipses in 2007 Viewing Viewing from Oceania is favoured for the eclipse because at the moment of greatest eclipse (103722 UTC the Moon was at the Zenith of French A partial Lunar eclipse took place on August 16, 2008, the second of two lunar eclipses in 2008 with the first being a total eclipse on February 20 A penumbral Lunar eclipse will take place on August 6 2009 the third of four lunar eclipses in 2009


See also

Lunar eclipse photo galleries

References

  1. ^ Hannu Karttunen. An eclipse is an astronomical event that occurs when one Celestial object moves into the shadow of another A solar eclipse occurs when the Moon passes between the Sun and the Earth so that the Sun is wholly or partially obscured For other uses of the word "umbra" see Umbra (disambiguation. The orbit of the Moon around the Earth is completed in approximately 27 Christopher Columbus (1451 &ndash May 20 1506 was an Italian Navigator, colonizer 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. Relation to other lunar eclipses This eclipse is the second of four Metonic cycle lunar eclipses on the same date May 15-16 each separated by 19 years Photo gallery Relation to other lunar eclipses This eclipse is the second of four Metonic cycle lunar eclipses on the same date November 8-9 each Relation to other lunar eclipses This eclipse is the third of four Metonic cycle lunar eclipses on the same date October 28-29 each separated by 19 years Viewing The whole event was visible from Europe, Africa, parts of South America, and some areas of North America, Asia, and Viewing Viewing from Oceania is favoured for the eclipse because at the moment of greatest eclipse (103722 UTC the Moon was at the Zenith of French A total Lunar eclipse occurred on the evening of Wednesday February 20, and morning of Thursday February 21, 2008. Fundamental Astronomy. Springer.
  2. ^ John Hammond. "Weather Centre: Astronomical event threatened by the Great British weather", BBC News, 15 May 2003. Retrieved on 2008-02-20. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1472 - Orkney and Shetland are left by Norway to Scotland, due to a Dowry payment  
  3. ^ Paul Deans and Alan M. MacRobert. Observing and Photographing Lunar Eclipses. Sky and Telescope.
  4. ^ Total Lunar Eclipse: 3 March 2007. NASA Eclipse Page. NASA (2008). Retrieved on 2008-02-20. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1472 - Orkney and Shetland are left by Norway to Scotland, due to a Dowry payment
  5. ^ Total Lunar Eclipse: 28 August 2007. NASA Eclipse Page. NASA (2008). Retrieved on 2008-02-20. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1472 - Orkney and Shetland are left by Norway to Scotland, due to a Dowry payment
  6. ^ Total Lunar Eclipse: 20 February 2008. NASA Eclipse Page. NASA (2008). Retrieved on 2008-02-20. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1472 - Orkney and Shetland are left by Norway to Scotland, due to a Dowry payment

External links


Dictionary

lunar eclipse

-noun

  1. (astronomy) A phenomenon occuring when the Earth casts a shadow over the Moon.
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