Lunar eclipse: Difference between revisions

Browse history interactively ← Previous edit Next edit →Content deleted Content addedVisual WikitextInline

Revision as of 10:05, 30 September 2014 view sourceTomruen (talk \| contribs)Autopatrolled, Extended confirmed users, Pending changes reviewers119,881 edits Add next eclipse diagram on the top← Previous edit		Revision as of 22:18, 1 October 2014 view source Fdizile (talk \| contribs)Extended confirmed users754 edits Clean up Fixing style/layout errorsTag: Visual edit Next edit →
Line 3:		Line 3:
	]]]		]]]
	]]]		]]]
			{{Ambox\|nocat = true\|text = The next Lunar Eclipse will take place on "October 8th, 2014"}}

	A '''lunar eclipse''' occurs when the ] passes directly behind the ] into its ] (shadow). This can occur only when the Sun, Earth, and Moon are aligned (in "]") exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a ]. The type and length of an ] depend upon the Moon's location relative to its ]s.		A '''lunar eclipse''' occurs when the ] passes directly behind the ] into its ] (shadow). This can occur only when the Sun, Earth, and Moon are aligned (in "]") exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a ]. The type and length of an ] depend upon the Moon's location relative to its ]s.

Revision as of 22:18, 1 October 2014

For other uses, see Lunar eclipse (disambiguation). Not to be confused with Solar eclipse.

The next Lunar Eclipse will take place on "October 8th, 2014"

A 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 dimmer than the full moon.

For the date of the next eclipse see the section Recent and forthcoming lunar eclipses.

Types of lunar 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.

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.

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. Earth's penumbra touches the Moon's outer limb.
U1 (Second contact): Beginning of the partial eclipse. Earth's umbra touches the Moon's outer limb.
U2 (Third contact): Beginning of the total eclipse. The Moon's surface is entirely within Earth's umbra.
Greatest eclipse: The peak stage of the total eclipse. The Moon is at its closest to the center of Earth's umbra.
U3 (Fourth contact): End of the total eclipse. The Moon's outer limb exits Earth's umbra.
U4 (Fifth contact): End of the partial eclipse. Earth's umbra leaves the Moon's surface.
P4 (Sixth contact): End of the penumbral eclipse. Earth's penumbra no longer makes contact with the Moon.

Appearance

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.

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.

Danjon scale

The following scale (the Danjon scale) was devised by André Danjon 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.

Lunar eclipse in mythology

Several cultures have myths related to lunar eclipses. The Egyptians saw the eclipse as a sow swallowing the moon for a short time; other cultures view the eclipse as the moon being swallowed by other animals, such as a jaguar in Mayan tradition, or a three legged toad in China. Some societies thought it was a demon swallowing the moon, and that they could chase it away by throwing stones and curses at it.

Blood moon

Due to its reddish color, a total eclipse of the moon is sometimes referred to as a blood moon. In addition, in the 2010s the media started to associate the term "blood moon" with the four full moons of a lunar tetrad, especially the 2014-2015 tetrad coinciding with the feasts of Passover and Tabernacles. A lunar tetrad is a consecutive sequence of four lunar eclipses, spaced six months apart.

Occurrence

See also: Saros (astronomy) and Eclipse cycle

Every year there are at least two lunar eclipses and as many as five, 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 like the saros.

Recent and forthcoming lunar eclipses

Main article: List of 21st-century lunar eclipses Further information: Lists of lunar eclipses

Eclipses only occur during an eclipse season, when the Sun is close to either the ascending or descending node of the Moon.

Lunar eclipses
1998–2002	2002–2005	2006–2009	2009–2013 2013-2016 (below)	2020–2023	2024–2027

This eclipse is a member of a semester series. An eclipse in a semester series of lunar eclipses repeats approximately every 177 days and 4 hours (a semester) at alternating nodes of the Moon's orbit.

The penumbral lunar eclipse on May 25, 2013 occurs in the previous lunar year eclipse set, and the penumbral lunar eclipse on August 18, 2016 occurs in the next lunar year eclipse set.

Lunar eclipse series sets from 2013 to 2016
Ascending node				Descending node
Saros	Date Viewing	Type Chart	Gamma	Saros	Date Viewing	Type Chart	Gamma
112	2013 Apr 25	Partial	−1.0121	117	2013 Oct 18	Penumbral	1.1508
122	2014 Apr 15	Total	−0.3017	127	2014 Oct 08	Total	0.3827
132	2015 Apr 04	Total	0.4460	137	2015 Sep 28	Total	−0.3296
142	2016 Mar 23	Penumbral	1.1592	147	2016 Sep 16	Penumbral	−1.0549

Simulation

Simulation of the appearance of the moon just before, during and just after a total lunar eclipse (the October 8, 2014 one in this example)

References

Hannu Karttunen. Fundamental Astronomy. Springer.
Clarke, Kevin. "On the nature of eclipses". Inconstant Moon. Cyclopedia Selenica. Retrieved 19 December 2010.
Fred Espenak and Jean Meeus. "Visual Appearance of Lunar Eclipses". NASA. The troposphere and stratosphere act together as a ring-shaped lens that refracts heavily reddened sunlight into Earth's umbral shadow {{cite web}}: Cite has empty unknown parameter: |1= (help)
"In Search of Selenelion". Observing Blog - SkyandTelescope.com. 2010-06-26. Retrieved 2011-12-08.
Paul Deans and Alan M. MacRobert. "Observing and Photographing Lunar Eclipses". Sky and Telescope.
"The Lunar Eclipse: Tidbits Behind the Phenomenon?". 2007-28-15. Retrieved 2011-12-02. {{cite web}}: Check date values in: |date= (help)
Nigro, Nicholas (2010). Knack Night Sky: Decoding the Solar System, from Constellations to Black Holes. Globe Pequot. pp. 214–5. ISBN 978-0-7627-6604-8.
Sappenfield, Mark (13 April 2014). "Blood Moon to arrive Monday night. What is a Blood Moon?". Christian Science Monitor. Retrieved 30 May 2014.
"What is a Blood Moon?". Earth & Sky. 24 April 2014. Retrieved 30 May 2014.
van Gent, R.H. "Solar- and Lunar-Eclipse Predictions from Antiquity to the Present". A Catalogue of Eclipse Cycles. Utrecht University. Retrieved 6 October 2018.

External links

v t e Moon
Outline
Physical properties	Internal structure Topography Atmosphere Gravity field Hill sphere Magnetic field Sodium tail Moonlight Earthshine
Orbit	Lunar distance Orbital elements Distance Perigee and apogee Libration Nodes Nodal period Precession Syzygy New moon Full moon Eclipses Lunar eclipse Total penumbral lunar eclipse Tetrad Solar eclipse Solar eclipses on the Moon Eclipse cycle Supermoon Tide Tidal force Tidal locking Tidal acceleration Tidal range Lunar station
Surface and features	Selenography Terminator Limb Hemispheres Near side Far side Poles North pole South pole Face Maria List Mountains Peak of eternal light Valleys Volcanic features Domes Calderas Lava tubes Craters List Ray systems Permanently shadowed craters South Pole–Aitken basin Soil swirls Rilles Wrinkle ridges Rocks Lunar basalt 70017 Changesite-(Y) Water Space weathering Micrometeorite Sputtering Quakes Transient lunar phenomenon Selenographic coordinate system
Science	Observation Libration Lunar theory Origin Giant-impact hypothesis Theia Lunar magma ocean Geology Timescale Late Heavy Bombardment Lunar meteorites KREEP Volcanism Experiments Lunar laser ranging ALSEP Lunar sample displays Apollo 11 Apollo 17 Lunar seismology
Exploration	Missions Apollo program Explorers Probes Landing Colonization Moonbase Tourism Lunar resources
Time-telling and navigation	Lunar calendar Lunisolar calendar Month Lunar month Nodal period Fortnight Sennight Lunar station Lunar distance
Phases and names	New Full Names Crescent Super and micro Blood Blue Black Dark Wet Tetrad
Daily phenomena	Moonrise Meridian passage Moonset
Related	Lunar deities Lunar effect Earth phase Moon illusion Pareidolia Man in the Moon Moon rabbit Craters named after people Artificial objects on the Moon Memorials on the Moon Moon in science fiction list Apollo era futuristic exploration Hollow Moon Moon landing conspiracy theories Moon Treaty "Moon is made of green cheese" Natural satellite Double planet Lilith (hypothetical second moon) Splitting of the Moon
Category