Vani’s Musings

An Eclispse

Posted on: March 3, 2007

 An eclipse (Greek verb: ekleipô, “to vanish”, though it derives from the prefix ‘ex-‘, “away from”, and Greek ‘leipein’, “to leave”) is an astronomical event that occurs when one celestial object moves into the shadow of another. The term is most often used to describe either a solar eclipse, when the Moon’s shadow crosses Earth’s surface, or a lunar eclipse, when the Moon moves into the shadow of Earth.

The phase known as New Moon cannot actually be seen because the illuminated side of the Moon is then pointed away from Earth. The rest of the phases are familiar to all of us as the Moon cycles through them month after month. As a matter of fact, the word month is derived from the Moon’s 29.5-day period.When the Moon is Full, it rises at sunset and is visible all night long. At the end of the night, the Full Moon sets just as the Sun rises. None of the Moon’s other phases have this unique characteristic. It happens because the Moon is directly opposite the Sun in the sky when the Moon is Full. Full Moon also has special significance with regard to eclipses. 

An eclipse of the Moon (or lunar eclipse) can only occur at Full Moon, and only if the Moon passes through some portion of the Earth’s shadow. The shadow is actually composed of two cone-shaped components, one nested inside the other. The outer or penumbral shadow is a zone where the Earth blocks part but not all of the Sun’s rays from reaching the Moon. In contrast, the inner or umbral shadow is a region where the Earth blocks all direct sunlight from reaching the Moon.

Astronomers recognize three basic types of lunar eclipses:

 1. Penumbral Lunar Eclipse

·         The Moon passes through Earth’s penumbral shadow.

·         These events are of only academic interest since they are subtle and quite difficult to observe.

2. Partial Lunar Eclipse

 ·         A portion of the Moon passes through Earth’s umbral shadow.

 ·         These events are easy to see, even with the unaided eye.

3. Total Lunar Eclipse

 ·         The entire Moon passes through Earth’s umbral shadow.

·         These events are quite striking for the vibrant range of colors the Moon can take on during the total phase (i.e. – totality).

The Moon’s orbit around Earth is actually tipped about 5 degrees to Earth’s orbit around the Sun. This means that the Moon spends most of the time either above or below the plane of Earth’s orbit. And the plane of Earth’s orbit around the Sun is important because Earth’s shadows lie exactly in the same plane. During Full Moon, our natural satellite usually passes above or below Earth’s shadows and misses them entirely. No eclipse takes place. But two to four times each year, the Moon passes through some portion of the Earth’s penumbral or umbral shadows and one of the above three types of eclipses occurs.

 When an eclipse of the Moon takes place, everyone on the night side of Earth can see it. About 35% of all eclipses are of the penumbral type, which are very difficult to detect, even with a telescope. Another 30% are partial eclipses, which are easy to see with the unaided eye. The final 35% or so are total eclipses, and these are quite extraordinary events to behold.

During a total lunar eclipse, the Earth blocks the Sun’s light from reaching the Moon. Astronauts on the Moon would then see the Earth eclipsing the Sun. (They would see a bright red ring around the Earth as they watched all the sunrises and sunsets happening simultaneously around the world) While the Moon remains completely within Earth’s umbral shadow, indirect sunlight still manages to reach and illuminate it. However, this sunlight must first pass deep through the Earth’s atmosphere, which filters out most of the blue colored light. The remaining light is a deep red or orange in color and is much dimmer than pure white sunlight. Earth’s atmosphere also bends or refracts some of this light so that a small fraction of it can reach and illuminate the Moon.

 All total eclipses start with a penumbral followed by a partial eclipse, and end with a partial followed by a penumbral eclipse (the total eclipse is sandwiched in the middle). The penumbral phases of the eclipse are quite difficult to see, even with a telescope. However, partial and total eclipses are easy to observe, even with the naked eye.

Observing Lunar Eclipses

Unlike solar eclipses, lunar eclipses are completely safe to watch. There is no need for any kind of protective filters. It isn’t even necessary to use a telescope. It can be watched with the naked eye, a set of binoculars may improve the image.Amateur astronomers can actually make some useful observations during total eclipses. It’s impossible to predict exactly how dark the Moon will appear during totality. The color can also vary from dark gray or brown, through a range of shades of red and bright orange. The color and brightness depend on the amount of dust in Earth’s atmosphere during the eclipse.

 Tomorrow, 4th March, a Total Lunar Eclispse, will occur, and will be visible throughout India. Weather permitting, we shall be able to watch and enjoy this magic moment of nature.


4 Responses to "An Eclispse"

Thanks for the gyaan madam 😉

Missed watching the eclipse, but Prashanth made me realise it thru the pics here!!

Nice timely post, Vani madam 😐

@Srik, thanks for linking 🙂

full toss Vani!

Eclipse of earth-u is when the shadow of my son-u falls on this Earth-u. 😀 who can forget this famous line s of Typical TPKALl

Eclipse of the earth-u may be happening every in your respective house 🙂

but the eclipse of moon-u occurred on Sunday… sorry sunday midnightu andre monday… but when this eclipsu… o(va)ccursuuu we all will hav tough timuuuu.. abhyanjana… upavasa…gods gella bath..u… manegella punyarchane ityadi ityadi… otnalli total (Gruha) Na

Nice info vani about the eclipse..uu….

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