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The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast.
These names are most often used for the shadows cast by celestial bodies, though they are sometimes used to describe levels, such as in sunspots.
The umbra (Latin for "shadow") is the innermost and darkest part of a shadow, where the light source is completely blocked by the occluding body. An observer within the umbra experiences a total occultation. The umbra of a round body occluding a round light source forms a right circular cone. When viewed from the cone's apex, the two bodies appear the same size.
The distance from the Moon to the apex of its umbra is roughly equal to that between the Moon and Earth: 384,402 km (238,856 mi). Since Earth's diameter is 3.7 times the Moon's, its umbra extends correspondingly farther: roughly 1.4 million km (870,000 mi). [1]
The penumbra (from the Latin paene "almost, nearly" and umbra "shadow") is the region in which only a portion of the light source is obscured by the occluding body. An observer in the penumbra experiences a partial eclipse. An alternative definition is that the penumbra is the region where some or all of the light source is obscured (i.e., the umbra is a subset of the penumbra). For example, NASA's Navigation and Ancillary Information Facility defines that a body in the umbra is also within the penumbra. [2]
The antumbra (from the Latin ante "before" and umbra "shadow") is the region from which the occluding body appears entirely within the disc of the light source. An observer in this region experiences an annular eclipse, in which a bright ring is visible around the eclipsing body. If the observer moves closer to the light source, the apparent size of the occluding body increases until it causes a full umbra. [3]
An eclipse is an astronomical event which occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three celestial objects is known as a syzygy. An eclipse is the result of either an occultation or a transit. A "deep eclipse" is when a small astronomical object is behind a bigger one.
A lunar eclipse is an astronomical event that occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. Such an alignment occurs during an eclipse season, approximately every six months, during the full moon phase, when the Moon's orbital plane is closest to the plane of the Earth's orbit.
A shadow is a dark area where light from a light source is blocked by an object. It occupies all of the three-dimensional volume behind an object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or a reverse projection of the object blocking the light.
An annular solar eclipse occurred at the Moon's descending node of the orbit on October 3, 2005, with a magnitude of 0.958. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Occurring only 4.8 days after apogee, the Moon's apparent diameter was smaller. It was visible from a narrow corridor through the Iberian peninsula and Africa and Brazil. A partial eclipse was seen from the much broader path of the Moon's penumbra, including all of Europe, Africa and southwestern Asia. The Sun was 96% covered in a moderate annular eclipse, lasting 4 minutes and 32 seconds and covering a broad path up to 162 km wide. The next solar eclipse in Africa occurred just 6 months later.
The magnitude of eclipse is the fraction of the angular diameter of a celestial body being eclipsed. This applies to all celestial eclipses. The magnitude of a partial or annular solar eclipse is always between 0.0 and 1.0, while the magnitude of a total solar eclipse is always greater than or equal to 1.0, and has a theoretically maximum value of around 1.12.
A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season in its new moon phase, when the Moon's orbital plane is closest to the plane of Earth's orbit. In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses, only part of the Sun is obscured. Unlike a lunar eclipse, which may be viewed from anywhere on the night side of Earth, a solar eclipse can only be viewed from a relatively small area of the world. As such, although total solar eclipses occur somewhere on Earth every 18 months on average, they recur at any given place only once every 360 to 410 years.
A total lunar eclipse took place on 15 April 2014. It was the first of two total lunar eclipses in 2014, and the first in a tetrad. Subsequent eclipses in the tetrad are those of 8 October 2014, 4 April 2015, and 28 September 2015. Occurring 6.7 days after apogee, the Moon's apparent diameter was smaller.
A partial lunar eclipse took place on Saturday, June 25, 1983, the first of two lunar eclipses in 1983 with an umbral eclipse magnitude of 0.33479. A partial lunar eclipse happens when the Earth moves between the Sun and the Full Moon, but they are not precisely aligned. Only part of the Moon's visible surface moves into the dark part of the Earth's shadow. A partial lunar eclipse occurs when the Earth moves between the Sun and Moon but the three celestial bodies do not form a straight line in space. When that happens, a small part of the Moon's surface is covered by the darkest, central part of the Earth's shadow, called the umbra. The rest of the Moon is covered by the outer part of the Earth's shadow called the penumbra. The Earth's shadow on the moon was clearly visible in this eclipse, with 33% of the Moon in shadow; the partial eclipse lasted for 2 hours and 15 minutes.
A partial lunar eclipse occurred on Tuesday, July 25, 1972 and Wednesday, July 26, 1972, the second of two lunar eclipses in 1972 with an umbral eclipse magnitude of 0.54271. A partial lunar eclipse occurs when the Earth moves between the Sun and Moon but the three celestial bodies do not form a straight line in space. When that happens, a small part of the Moon's surface is covered by the darkest, central part of the Earth's shadow, called the umbra. The rest of the Moon is covered by the outer part of the Earth's shadow called the penumbra. The moon's apparent diameter was 3.2 arcseconds smaller than the January 30, 1972 lunar eclipse.
A partial lunar eclipse took place on Saturday, July 6, 1963 with an umbral eclipse magnitude of 0.70602. The Moon was strikingly shadowed in this deep partial eclipse which lasted 3 hours exactly, with 71% of the Moon in darkness at maximum. A partial lunar eclipse occurs when the Earth moves between the Sun and Moon but the three celestial bodies do not form a straight line in space. When that happens, a small part of the Moon's surface is covered by the darkest, central part of the Earth's shadow, called the umbra. The rest of the Moon is covered by the outer part of the Earth's shadow called the penumbra. It was the second of three lunar eclipses in 1963, the first was a penumbral lunar eclipse on January 9, 1963 and the third and last was on December 30, 1963.
A partial lunar eclipse took place on Tuesday, November 29, 1955 with an umbral eclipse magnitude of 0.11899. A partial lunar eclipse happens when the Earth moves between the Sun and the Full Moon, but they are not precisely aligned. Only part of the Moon's visible surface moves into the dark part of the Earth's shadow. A partial lunar eclipse occurs when the Earth moves between the Sun and Moon but the three celestial bodies do not form a straight line in space. When that happens, a small part of the Moon's surface is covered by the darkest, central part of the Earth's shadow, called the umbra. The rest of the Moon is covered by the outer part of the Earth's shadow called the penumbra. It was the second of two lunar eclipses in 1955, first being the penumbral lunar eclipse on June 5. It also occurred near perigee, making such event a supermoon.
A penumbral lunar eclipse took place at the Moon's ascending of the orbit on Sunday, June 5, 1955, with a penumbral eclipse magnitude of 0.62181 (62.181%). A penumbral lunar eclipse takes place when the Moon moves through the faint, outer part of Earth's shadow, the penumbra. This type of eclipse is not as dramatic as other types of lunar eclipses and is often mistaken for a regular Full Moon. The Moon shines because its surface reflects the Sun's rays. A lunar eclipse happens when the Earth comes between the Sun and the Moon and blocks some or all of the Sun's light from reaching the Moon. A penumbral lunar eclipse occurs when the Sun, Earth, and the Moon are imperfectly aligned. When this happens, the Earth blocks some of the Sun's light from directly reaching the Moon's surface and covers all or part of the Moon with the outer part of its shadow, also known as the penumbra. Since the penumbra is much fainter than the dark core of the Earth's shadow, the umbra, a penumbral eclipse of the Moon is often difficult to tell apart from a normal Full Moon. Occurring only 0.5 days after apogee, the moon's apparent diameter was 6.5% smaller than average.
A total penumbral lunar eclipse is a lunar eclipse that occurs when the Moon becomes completely immersed in the penumbral cone of the Earth without touching the umbra.
Gamma of an eclipse describes how centrally the shadow of the Moon or Earth strikes the other body. This distance, measured at the moment when the axis of the shadow cone passes closest to the center of the Earth or Moon, is stated as a fraction of the equatorial radius of the Earth or Moon.
The solar eclipse of May 20, 2012 was an annular solar eclipse that was visible in a band spanning through Eastern Asia, the Pacific Ocean, and North America. As a partial solar eclipse, it was visible from northern Greenland to Hawaii, and from eastern Indonesia at sunrise to northwestern Mexico at sunset. The moon's apparent diameter was smaller because the eclipse was occurring only 32 1/2 hours after apogee.
An annular solar eclipse will occur on October 2, 2024. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
The earliest scientifically useful photograph of a total solar eclipse was made by Julius Berkowski at the Royal Observatory in Königsberg, Prussia, on July 28, 1851. This was the first occasion that an accurate photographic image of a solar eclipse was recorded.
Earth's shadow is the shadow that Earth itself casts through its atmosphere and into outer space, toward the antisolar point. During the twilight period, the shadow's visible fringe – sometimes called the dark segment or twilight wedge – appears as a dark and diffuse band just above the horizon, most distinct when the sky is clear.
The Besselian elements are a set of values used to calculate and predict the local circumstances of occultations for an observer on Earth. This method is particularly used for solar eclipses, but is also applied for occultations of stars or planets by the Moon and transits of Venus or Mercury. In addition, for lunar eclipses a similar method is used, in which the shadow is cast on the Moon instead of the Earth.
Solar eclipses on the Moon are caused when the planet Earth passes in front of the Sun and blocks its light. Viewers on Earth experience a lunar eclipse during a solar eclipse on the Moon.
