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CENTURY’S LONGEST PARTIAL LUNAR ECLIPSE TO OCCUR ON NOVEMBER 19, 2021 (SAMYA MUKHERJEE)

Updated: Jan 10, 2022

A lunar eclipse occurs when the Earth comes in between the Moon and the Sun. When the Sun, the Earth and the Moon are not fully aligned; the Earth obstructs some of the sun-light from reaching the Moon – this causes a slight darkening of the Moon. While a total lunar eclipse occurs when the Moon and the Sun are on opposite sides of the Earth, a partial lunar eclipse happens when only part of the earth’s shadow covers the Moon. Meanwhile, when the Moon travels through the faint penumbral portion of the shadow of the Earth; thus happens a penumbral lunar eclipse. The last lunar eclipse of the year 2021 is going to take place on 19th November. Although it is a partial lunar eclipse, 97 percent of the surface of the moon will be covered by the shadow of the earth; making it an almost total lunar eclipse. The lunar eclipse of 19th November 2021 is going to be the century’s longest partial lunar eclipse; which will last for 3 hours 28 minutes and 23 seconds to be exact - that’s more than twice the duration of the longest total lunar eclipse of the 21st century, that lasted for 1 hour 42 minutes. The forthcoming eclipse is also the longest lunar eclipse in last 580 years. For a partial lunar eclipse to occur, the conditions required is a fullmoon aligned in a straight line with Sun and the Earth. However, a partial lunar eclipse does not happen on every full moon since the lunar body is inclined on its orbital plane at an angle of five deegres to the Earth’s orbital plane (ecliptic) around the Sun. 2 The eclipse will be visible from any location where the moon is above the horizon at the time. Thus, the eclipse is going to be witnessed in large parts of Australia, East Asia, North America, South America and the Pacific region. In the United States, all 50 states will be able to view the partial lunar eclipse. The eclipse is expected to be seen in the North-eastern states of India such as Assam and Arunachal Pradesh. The eclipse is expected to be at peak at around 1:30 PM on 19th November, with the earth hiding 97 percent of the moon. The celestial body will acquire a reddish hue during this period. The reddening of the Moon : It might have been observed that the Moon does not disappear entirely from our view, even during a total lunar eclipse. Instead, it turns rusty red, a phenomenon sometimes referred to as the ‘Blood Moon’. Why does the Moon turn red during the lunar eclipse? Well, it is because of the same reason as the reason behind the sky is blue. White light from the sun is composed of different primary colours – violet, indigo, blue, green, yellow, orange, red. When the Moon aligns with the Earth and the Sun; even though the Earth’s umbra completely blocks the sunlight, it bends around our planet to reach the surface of the Moon. As the sunlight travels through the Earth’s atmosphere the shorter, bluer wavelengths are filtered out. As a result, the Moon is washed in longer, redder wavelengths. This phenomenon is known as ‘Rayleigh scattering’ and it is the reason why the moon turns red during a total lunar eclipse. The eclipse is set to be a very deep eclipse with about 97 percent of the Moon’s disk passing through the dark inner part of the Earth’s shadow – its umbra – to leave “a tiny, silvery silver of the Moon’s southern edge peeking out” (quoted from Sky and Telescope Magazine). There is no harm in looking at the lunar eclipse with naked eyes or though a telescope, in contrast to a solar eclipse. Although a 3 telescope or a pair of binoculars will enhance the view, to properly view the cosmic show. Why the eclipse is so long? : The partial lunar eclipse of November 19 will shatter records for the longest eclipse, becoming longer than a total lunar eclipse. The reason, this celestial phenomenon will be unusually long, is that it comes 41 hours after the Moon reaches apogee, its farthest point from the Earth. The farther away the Moon is, the longer it takes to travel along, resulting in more time to move out of Earth’s shadow. Record of the eclipse : The partial lunar eclipse of November 19 will sustain its record for another four thousand years as the sixhour long partial lunar eclipse will likely happen on October 9, 2489. The last such long lunar eclipse was on 9th Novenber 2003; spanning six hours and three minutes. However, it was not partial but a total lunar eclipse. At least two partial lunar eclipses happen every year, but total lunar eclipses are rare. Unlike solar eclipses, it is safe to look at lunar eclipses. What next? : A lunar eclipse is always followed or preceded by a solar eclipse. This time, a total solar eclipse will take place on December 4, but unfortunately, it will be exclusive to penguins and a handful of researchers living on the South Pole. So, the lunar eclipse of November 19, 2021 is the last eclipse of the year that a part of the world can view. ************************************************* 4

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CENTURY’S LONGEST PARTIAL LUNAR ECLIPSE TO OCCUR ON NOVEMBER 19, 2021 (SAMYA MUKHERJEE)

Updated: Jan 10, 2022

A lunar eclipse occurs when the Earth comes in between the Moon and the Sun. When the Sun, the Earth and the Moon are not fully aligned; the Earth obstructs some of the sun-light from reaching the Moon – this causes a slight darkening of the Moon. While a total lunar eclipse occurs when the Moon and the Sun are on opposite sides of the Earth, a partial lunar eclipse happens when only part of the earth’s shadow covers the Moon. Meanwhile, when the Moon travels through the faint penumbral portion of the shadow of the Earth; thus happens a penumbral lunar eclipse. The last lunar eclipse of the year 2021 is going to take place on 19th November. Although it is a partial lunar eclipse, 97 percent of the surface of the moon will be covered by the shadow of the earth; making it an almost total lunar eclipse. The lunar eclipse of 19th November 2021 is going to be the century’s longest partial lunar eclipse; which will last for 3 hours 28 minutes and 23 seconds to be exact - that’s more than twice the duration of the longest total lunar eclipse of the 21st century, that lasted for 1 hour 42 minutes. The forthcoming eclipse is also the longest lunar eclipse in last 580 years. For a partial lunar eclipse to occur, the conditions required is a fullmoon aligned in a straight line with Sun and the Earth. However, a partial lunar eclipse does not happen on every full moon since the lunar body is inclined on its orbital plane at an angle of five deegres to the Earth’s orbital plane (ecliptic) around the Sun. 2 The eclipse will be visible from any location where the moon is above the horizon at the time. Thus, the eclipse is going to be witnessed in large parts of Australia, East Asia, North America, South America and the Pacific region. In the United States, all 50 states will be able to view the partial lunar eclipse. The eclipse is expected to be seen in the North-eastern states of India such as Assam and Arunachal Pradesh. The eclipse is expected to be at peak at around 1:30 PM on 19th November, with the earth hiding 97 percent of the moon. The celestial body will acquire a reddish hue during this period. The reddening of the Moon : It might have been observed that the Moon does not disappear entirely from our view, even during a total lunar eclipse. Instead, it turns rusty red, a phenomenon sometimes referred to as the ‘Blood Moon’. Why does the Moon turn red during the lunar eclipse? Well, it is because of the same reason as the reason behind the sky is blue. White light from the sun is composed of different primary colours – violet, indigo, blue, green, yellow, orange, red. When the Moon aligns with the Earth and the Sun; even though the Earth’s umbra completely blocks the sunlight, it bends around our planet to reach the surface of the Moon. As the sunlight travels through the Earth’s atmosphere the shorter, bluer wavelengths are filtered out. As a result, the Moon is washed in longer, redder wavelengths. This phenomenon is known as ‘Rayleigh scattering’ and it is the reason why the moon turns red during a total lunar eclipse. The eclipse is set to be a very deep eclipse with about 97 percent of the Moon’s disk passing through the dark inner part of the Earth’s shadow – its umbra – to leave “a tiny, silvery silver of the Moon’s southern edge peeking out” (quoted from Sky and Telescope Magazine). There is no harm in looking at the lunar eclipse with naked eyes or though a telescope, in contrast to a solar eclipse. Although a 3 telescope or a pair of binoculars will enhance the view, to properly view the cosmic show. Why the eclipse is so long? : The partial lunar eclipse of November 19 will shatter records for the longest eclipse, becoming longer than a total lunar eclipse. The reason, this celestial phenomenon will be unusually long, is that it comes 41 hours after the Moon reaches apogee, its farthest point from the Earth. The farther away the Moon is, the longer it takes to travel along, resulting in more time to move out of Earth’s shadow. Record of the eclipse : The partial lunar eclipse of November 19 will sustain its record for another four thousand years as the sixhour long partial lunar eclipse will likely happen on October 9, 2489. The last such long lunar eclipse was on 9th Novenber 2003; spanning six hours and three minutes. However, it was not partial but a total lunar eclipse. At least two partial lunar eclipses happen every year, but total lunar eclipses are rare. Unlike solar eclipses, it is safe to look at lunar eclipses. What next? : A lunar eclipse is always followed or preceded by a solar eclipse. This time, a total solar eclipse will take place on December 4, but unfortunately, it will be exclusive to penguins and a handful of researchers living on the South Pole. So, the lunar eclipse of November 19, 2021 is the last eclipse of the year that a part of the world can view. ************************************************* 4

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