Show Lunar eclipses occur at full moon, when the Earth lies between Moon and Sun and so intercepts the light from the Sun. The Moon usually appears red or copper-colored during such events, as a portion of the red part of the visible solar spectrum is refracted by the Earth's atmosphere and faintly illuminates the Moon. From: Encyclopedia of the Solar System (Second Edition), 2007  A solar eclipse happens at new moon, when the moon passes between the sun and Earth. A lunar eclipse happens at full moon, when the Earth, sun and moon align in space, with Earth between the sun and moon. During a lunar eclipse, Earth’s shadow falls on the full moon, darkening the moon’s face and – at mid-eclipse – sometimes turning it a coppery red. We typically have between four and seven eclipses – some partial, some total, some lunar and some solar every year. Why aren’t there eclipses at every full and new moon? The moon takes about a month to orbit around the Earth. If the moon orbited in the same plane as the ecliptic – Earth’s orbital plane – we would have a minimum of two eclipses every month. There’d be an eclipse of the moon at every full moon. And, approximately two weeks later there’d be an eclipse of the sun at new moon for a total of at least 24 eclipses every year. Moon’s orbit is inclinedBut that doesn’t happen, and the reason is that the moon’s orbit around Earth is inclined to Earth’s orbit around the sun by about 5 degrees. Twice a month the moon intersects the ecliptic – Earth’s orbital plane – at points called nodes. If the moon is going from south to north in its orbit, it’s called an ascending node. If the moon is going from north to south, it’s a descending node. If the full moon or new moon sweeps appreciably close to one of these nodes, then an eclipse is not only possible – but inevitable. An eclipse does not come aloneSolar and lunar eclipses always come in pairs, with one following the other in a period of one fortnight (approximately two weeks). For example, the ascending node partial solar eclipse on April 30, 2022, was followed by a descending node total lunar eclipse on May 15-16, 2022. Then exactly six lunar months (six new moons) after the ascending node annular solar eclipse of April 30, 2022, there will be a descending node partial solar eclipse on October 25, 2022. And exactly six lunar months (six full moons) after this descending node total lunar eclipse on May 15-16, 2022, there will be an ascending node total lunar eclipse on November 8, 2022. Eclipse seasonsMore often than not, two eclipses – one solar and one lunar – occur in one eclipse season, a period lasting approximately 34 to 35 days. Sometimes, though, when the initial eclipse happens sufficiently early in the eclipse season, there can be three eclipses in one eclipse season (two solar and one lunar, or two lunar and one solar). This last happened in July-August 2020 (lunar/solar/lunar), and will next happen in June-July 2029 (solar/lunar/solar). Read more: How often are there 3 eclipses in a month? This year, in 2022, the middle of the eclipse season falls on May 15 and November 4. At the middle of an eclipse season, which recurs in periods of about 173 days, the lunar nodes are in exact alignment with the Earth and sun. The video below explains why a pair of eclipses happens when the new moon and full moon are closely aligned with the lunar nodes. There might be some unfamiliar words in this video, including ecliptic and node. The ecliptic is the plane of Earth’s orbit around the sun. The moon’s orbit is inclined to the plane of the ecliptic. The nodes are the two points where the moon’s orbit and the ecliptic intersect. Moon phases shift along the zodiac every monthRelative to the moon’s nodes, the moon’s phases recur about 30 degrees farther eastward (counterclockwise) along the zodiac each month. So the next pair of eclipses won’t be forthcoming for nearly another six calendar months (6 x 30 degrees = 180 degrees). Following the April 30 and May 15-16 eclipses, the next pair of eclipses falls on October 25 and November 8, 2022. The first pair of eclipses in 2023 are on November 20 (total solar eclipse), and May 5-6 (partial lunar eclipse). Node passages of the moon: 2001 to 2100 Phases of the moon: 2001 to 2100 The following new moon and full moon happen nearly 30 degrees farther eastward as measured by the constellations of the zodiac in about 29.5 days. But the moon returns to its node a good two days earlier than that, or in about 27.2 days. Even though the moon’s orbit is inclined to that of Earth – and even though there’s not an eclipse with every new and full moon – there are more eclipses than you might think. All are marvelous to behold. They’re a reminder that we live on a planet and a chance to experience falling in line with great worlds in space! Bottom line: If the Earth and moon orbited on the same plane around the sun, we’d have a total solar eclipse – and a total lunar eclipse – every month. But we don’t, because the moon’s orbit is inclined to Earth’s orbit by about 5 degrees. In 2022, there are four eclipses: two solar and two lunar. Read more: Partial solar eclipse on October 25, 2022 Read more: Total lunar eclipse on November 8, 2022 Visit EarthSky’s Best Places to Stargaze to find eclipse-viewing locations Post your eclipse photos to EarthSky Community Photos Donate: It means the world to us A lunar eclipse occurs when the Moon moves into the Earth's shadow.[1] This can occur only when the Sun, Earth, and Moon are exactly or very closely aligned (in syzygy) with Earth between the other two, which can happen only on the night of a full moon when the Moon is near either lunar node. The type and length of a lunar eclipse depend on the Moon's proximity to the lunar node.[citation needed] The reddish color of totally eclipsed Moon is caused by Earth completely blocking direct sunlight from reaching the Moon, with the only light reflected from the lunar surface has been refracted by Earth's atmosphere. This light appears reddish for the same reason that a sunset or sunrise does: the Rayleigh scattering of blue light. Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. A total lunar eclipse can last up to nearly 2 hours, while a total solar eclipse lasts only up to a few minutes at any given place, because the Moon's shadow is smaller. Also unlike solar eclipses, lunar eclipses are safe to view without any eye protection or special precautions, as they are dimmer than a normal full Moon. The symbol for a lunar eclipse (or indeed any body in the shadow of another) is For the date of the next eclipse, see § Recent and forthcoming lunar eclipses. A schematic diagram of the shadow cast by Earth. Within the umbra, the central region, the planet totally shields direct sunlight. In contrast, within the penumbra, the outer portion, the sunlight is only partially blocked. (Neither the Sun, Moon, and Earth sizes nor the distances between the bodies are to scale.) A total penumbral lunar eclipse dims the Moon in direct proportion to the area of the Sun's disk covered by Earth. This comparison of the Moon (within the southern part of Earth's shadow) during the penumbral lunar eclipse of January 1999 (left) and the Moon outside the shadow (right) shows this slight darkening. Earth's shadow can be divided into two distinctive parts: the umbra and penumbra. Earth totally occludes direct solar radiation within the umbra, the central region of the shadow. However, since the Sun's diameter appears about one-quarter of Earth's in the lunar sky, the planet only partially blocks direct sunlight within the penumbra, the outer portion of the shadow. Penumbral lunar eclipseThis occurs when the Moon passes through Earth's penumbra. The penumbra causes a subtle dimming of the lunar surface, which is only visible to the naked eye when about 70% of the Moon's diameter has immersed into Earth's penumbra.[2] A special type of penumbral eclipse is a total penumbral lunar eclipse, during which the Moon lies exclusively within Earth's penumbra. Total penumbral eclipses are rare, and when these occur, the portion of the Moon closest to the umbra may appear slightly darker than the rest of the lunar disk. Partial lunar eclipseThis occurs when only a portion of the Moon enters Earth's umbra, while a total lunar eclipse occurs when the entire Moon enters the planet's umbra. The Moon's average orbital speed is about 1.03 km/s (2,300 mph), or a little more than its diameter per hour, so totality may last up to nearly 107 minutes. Nevertheless, the total time between the first and the last contacts of the Moon's limb with Earth's shadow is much longer and could last up to 236 minutes.[3] Total lunar eclipseThis occurs when the Moon falls entirely within the Earth's umbra. Just prior to complete entry, the brightness of the lunar limb-- the curved edge of the Moon still being hit by direct sunlight-- will cause the rest of the Moon to appear comparatively dim. The moment the Moon enters a complete eclipse, the entire surface will become more or less uniformly bright. Later, as the Moon's opposite limb is struck by sunlight, the overall disk will again become obscured. This is because as viewed from the Earth, the brightness of a lunar limb is generally greater than that of the rest of the surface due to reflections from the many surface irregularities within the limb: sunlight striking these irregularities is always reflected back in greater quantities than that striking more central parts, and is why the edges of full moons generally appear brighter than the rest of the lunar surface. This is similar to the effect of velvet fabric over a convex curved surface which to an observer will appear darkest at the center of the curve. It will be true of any planetary body with little or no atmosphere and an irregular cratered surface (e.g., Mercury) when viewed opposite the Sun.[4] Central lunar eclipseThis is a total lunar eclipse during which the Moon passes through the centre of Earth's shadow, contacting the antisolar point. This type of lunar eclipse is relatively rare. The relative distance of the Moon from Earth at the time of an eclipse can affect the eclipse's duration. In particular, when the Moon is near apogee, the farthest point from Earth in its orbit, its orbital speed is the slowest. The diameter of Earth's umbra does not decrease appreciably within the changes in the Moon's orbital distance. Thus, the concurrence of a totally eclipsed Moon near apogee will lengthen the duration of totality. A view of the October 2014 lunar eclipse from Minneapolis, with the setting and partially eclipsed Moon appearing squashed just above the horizon just after sunrise (seen as sunlight shining on the tree in the right image) A selenelion or selenehelion, also called a horizontal eclipse, occurs where and when both the Sun and an eclipsed Moon can be observed at the same time. The event can only be observed just before sunset or just after sunrise, when both bodies will appear just above opposite horizons at nearly opposite points in the sky. A selenelion occurs during every total lunar eclipse-- it is an experience of the observer, not a planetary event separate from the lunar eclipse itself. Typically, observers on Earth located on high mountain ridges undergoing false sunrise or false sunset at the same moment of a total lunar eclipse will be able to experience it. Although during selenelion the Moon is completely within the Earth's umbra, both it and the Sun can be observed in the sky because atmospheric refraction causes each body to appear higher (i.e., more central) in the sky than its true geometric planetary position.[5] 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. Contact points relative to the Earth's umbral and penumbral shadows, here with the Moon near is descending node The timing of total lunar eclipses is determined by what are known as its "contacts" (moments of contact with Earth's shadow):[6] 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.The following scale (the Danjon scale) was devised by André Danjon for rating the overall darkness of lunar eclipses:[7] 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.A solar eclipse occurs in the daytime at new moon, when the Moon is between Earth and the Sun, while a lunar eclipse occurs at night at full moon, when Earth passes between the Sun and the Moon. The Moon does not completely darken as it passes through the umbra because Earth's atmosphere refracts sunlight into the shadow cone. There is often confusion between a solar eclipse and a lunar eclipse. While both involve interactions between the Sun, Earth, and the Moon, they are very different in their interactions. Lunar eclipse appearanceIn a lunar eclipse, the Moon often passes through two regions of Earth's shadow: an outer penumbra, where direct sunlight is dimmed, and an inner umbra, where indirect and much dimmer sunlight refracted by Earth's atmosphere shines on the Moon, leaving a reddish color. This can be seen in different exposures of a partial lunar eclipse, for example here with exposures of 1/80, 2/5, and 2 seconds. The Moon does not completely darken as it passes through the umbra because of the refraction of sunlight by Earth's atmosphere into the shadow cone; if Earth had no atmosphere, the Moon would be completely dark during the eclipse.[8] The reddish coloration arises because sunlight reaching the Moon must pass through a long and dense layer of Earth's atmosphere, where it is scattered. Shorter wavelengths are more likely to be scattered by the air molecules and small particles; thus, the longer wavelengths predominate by the time the light rays have penetrated the atmosphere. Human vision perceives this resulting light as red. This is the same effect that causes sunsets and sunrises to turn the sky a reddish color. An alternative way of conceiving this scenario is to realize that, as viewed from the Moon, the Sun would appear to be setting (or rising) behind Earth. From the Moon, a lunar eclipse would show a ring of reddish-orange light surrounding a silhouetted Earth in the lunar sky. 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. Christopher Columbus predicting a lunar eclipse. Several cultures have myths related to lunar eclipses or allude to the lunar eclipse as being a good or bad omen. 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 mythical three-legged toad known as Chan Chu 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.[9] The Ancient Greeks correctly believed the Earth was round and used the shadow from the lunar eclipse as evidence.[10] Some Hindus believe in the importance of bathing in the Ganges River following an eclipse because it will help to achieve salvation.[11] IncaSimilarly to the Mayans, the Incans believed that lunar eclipses occurred when a jaguar ate the Moon, which is why a blood moon looks red. The Incans also believed that once the jaguar finished eating the Moon, it could come down and devour all the animals on Earth, so they would take spears and shout at the Moon to keep it away.[12] MesopotamiansThe ancient Mesopotamians believed that a lunar eclipse was when the Moon was being attacked by seven demons. This attack was more than just one on the Moon, however, for the Mesopotamians linked what happened in the sky with what happened on the land, and because the king of Mesopotamia represented the land, the seven demons were thought to be also attacking the king. In order to prevent this attack on the king, the Mesopotamians made someone pretend to be the king so they would be attacked instead of the true king. After the lunar eclipse was over, the substitute king was made to disappear (possibly by poisoning).[12] ChineseIn some Chinese cultures, people would ring bells to prevent a dragon or other wild animals from biting the Moon.[13] In the 19th century, during a lunar eclipse, the Chinese navy fired its artillery because of this belief.[14] During the Zhou Dynasty (c. 1046–256 BC) in the Book of Songs, the sight of a Red Moon engulfed in darkness was believed to foreshadow famine or disease.[15]
Change to reddish cast Certain lunar eclipses have been referred to as "blood moons" in popular articles but this is not a scientifically-recognized term.[16] This term has been given two separate, but overlapping, meanings. The first, and simpler, meaning relates to the reddish color a totally eclipsed Moon takes on to observers on Earth.[17] As sunlight penetrates the atmosphere of Earth, the gaseous layer filters and refracts the rays in such a way that the green to violet wavelengths on the visible spectrum scatter more strongly than the red, thus giving the Moon a reddish cast.[18] The second meaning of "blood moon" has been derived from this apparent coloration by two fundamentalist Christian pastors, Mark Blitz and John Hagee.[16][19] They claimed that the 2014–15 "lunar tetrad" of four lunar eclipses coinciding with the feasts of Passover and Tabernacles matched the "moon turning to blood" described in the Book of Joel of the Hebrew Bible.[19] This tetrad was claimed to herald the Second Coming of Christ and the Rapture as described in the Book of Revelation on the date of the first of the eclipses in this sequence on April 15, 2014.[20] This multi-exposure sequence shows the August 2017 lunar eclipse visible from the ESO headquarters.[21] This collage shows the transitional stages of a lunar eclipse. At least two lunar eclipses and as many as five occur every year, although total lunar eclipses are significantly less common. If the date and time of an eclipse is known, the occurrences of upcoming eclipses are predictable using an eclipse cycle, like the saros. Recent and forthcoming lunar eclipsesEclipses occur only during an eclipse season, when the Sun appears to pass near either node of the Moon's orbit.
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At which position in its orbit was the Moon located during a total lunar eclipse
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