Longest Lunar Eclipse

An spectacular lunar eclipse will be taking place during the night of 27-28 July.  If weather permits, the entire cosmic event will be visible from Srinagar and other parts of the state. The penumbral eclipse will begin at quarter to eleven in night and end after Fajr, making it longest eclipse of the century.  The total eclipse will begin at quarter past one and end at quarter to three.  In the night of the eclipse, full moon is also at its farthest from the earth (Apogee) so it will look relatively smaller in the sky hence it is called micro moon in contrast to supermoon when it appears largest.

 A lunar eclipse occurs when the Moon passes behind the Earth so that the Earth blocks the Sun's rays from striking the Moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur during the night of a full moon. It might be expected that during every full moon  the Earth's shadow will fall on the Moon, causing a lunar eclipse.  Lunar eclipses are not observed every month because the plane of the Moon's orbit around the Earth is tilted by about five degrees with respect to the plane of Earth's orbit around the Sun. Thus, when a full moons occurs, the Moon usually lies to the north or south of a direct line through the Earth and Sun. Although a lunar eclipse can only occur when the Moon is  full, it must also be positioned very near the intersection of Earth's orbital plane about the Sun and the Moon's orbital plane about the Earth that is, at one of its nodes.

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. Due to the Sun’s large angular size, solar light is only partially blocked in the outer portion of the Earth’s shadow or penumbra. A penumbral eclipse occurs when the Moon passes through the Earth’s penumbra. 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.

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.

Since moon is a non luminous body, lunar eclipses (unlike Solar Eclipses) are completely safe to observe with the naked eye - no special equipment or filters are needed. Sometimes a Total Lunar Eclipse is best viewed without any optical aid, and just lying under the stars watching the change as the Moon first gets slightly darker (penumbral phase), then starts to get eaten away (partial phase), finally turning deep red or copper coloured as it enters totality. During a total lunar eclipse, the sun’s direct light is blocked by the earth and does not reach the moon. A small amount of the sunlight that passes through earth’s atmosphere, however, is refracted or “bent” towards the moon by the atmosphere and is reflected towards us on earth by the moon. Particles in the atmosphere also preferentially scatter away the bluer light of shorter wavelengths and only the redder light that has relatively longer wavelengths gets through, similar to the sunlight we see at sunset and sunrise. This redder light reaches the moon because of the bending (refraction). Therefore the moon appears copper-coloured during a total lunar eclipse. The exact colour will depend on the nature and quantity of the dust particles, water droplets and aerosols present in the earth’s atmosphere at that time. Hence it is an indicator of earths atmospheric pollution!

For sky-watchers there is another treat in the intervening night of 27-28 July. The red planet Mars will be aligned with Earth and Sun. Mars will be on the opposite side of the Sun and Earth and it will be visible throughout night. It can be seen in the vicinity of eclipsed moon. In fact Jupiter and Saturn will also be clearly visible during the night. It is summer time hence night picnics may be organized by all science and nature lovers in their neighbourhood. All astro-photographers, may aim their cameras towards sky. The eclipse is a unique opportunity to appreciate,  admire and celebrate the beauty and inspiration of this celestial experience.