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12-Solar Eclipse

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12-Solar Eclipse
List of Eclipses | Eclipses | Lular Eclipse

Eclipse means hiding. Thus in Solar Eclipse, the Sun is hidden from our eyes, and in Lunar Eclipse the Moon is hidden from our eyes. What is the reason of their hiding on certain days? There are some facts about them.

1. Solar Eclipse is always on New Moon day, and Lunar Eclipse is always on Full Moon day.
2. Both the Eclipses, Solar and Lunar, cannot be seen alike at all the places on the earth.
3. Since the Solar Eclipse are the results of periodic motion of the Moon round the Earth, there are regularities in the timing of the Eclipses that give cycles to the related Eclipses. These cycles can predict the future Eclipses.
4. Although both Eclipses with comparable frequencies, the Lunar Eclipse's frequency is more than the Solar ones. It is because the darkened Moon can be seen from anywhere in the nighttime.
5. A Lunar Eclipse can be seen by more people than the Solar Eclipse.
6. A Lunar Eclipse can last up to 3.5 hours, as opposed to Solar Eclipse which may last up to 7.5 minutes. Why? Because of the speed at which the Earth moves around the Sun, it is impossible for a Solar Eclipse to last more than 8 minutes.
7. While the Moon is always in a new phase during a Solar Eclipse, a Solar Eclipse does not occur every time the Moon is in the new phase. This is because the orbit of the Moon is tilted relative to the Earth's orbit around the Sun. This tilt is only 5 degrees, but it is enough that the alignment of the Earth, Moon, and Sun only occurs about once every six months. This holds true for Lunar Eclipses as well. In fact, Lunar and Solar Eclipses generally occur together; that is, if the alignment is correct for a Lunar Eclipse during the full phase of the Moon, it will also be correct for a Solar Eclipse during the next new phase of the Moon.
8. Solar Eclipses are fairly numerous, generally 2-5 per year, but the area covered on the ground is covered is very less - a few tens of miles only, that is why Lunar Eclipse is rarely in the path of Solar Eclipse. In any given location on Earth, a total Solar Eclipse happens only once in 360 years.

Solar Eclipse
Solar Eclipse always occurs on New Moon day, but it does not occur on every New Moon day. It occurs only when the Moon comes between the Sun and the earth and covers the Sun blocking the rays of the Sun reaching the earth and casts its shadow on the earth. In fact, two different cycles of the Moon affect the Solar Eclipse - one is its monthly cycle so the Sun is hidden from our eyes on New Moon day, and the other is gradual shift in orientation of the Moon's orbit. Only when these two are favorably combines then only can a Solar Eclipse occur.

Types of Solar Eclipse
There are mainly two types of Solar Eclipse - total, and partial. Partial Eclipse may be of two types - one in which the Sun is hidden only partially, two in which the Sun is also hidden partially but its apparent diameter can be seen against the shadow fallen on it. This is called Annular Eclipse. Any Solar Eclipse can of all the three types for different observers. 

Total Solar Eclipse is rare, so if you get an opportunity to look at it, never miss it, it is really interesting to see and experience a total Solar Eclipse. To see a total Solar Eclipse you have to be in the path of totality, and this path, sometimes 200 miles wide, never covers more than roughly 1/2% of the 1% area of the whole earth and often traverses upon seas or remote regions of the planet. Only fewer than 70 total Solar Eclipses occur in a century - this makes a chance for seeing a total Solar Eclipse for most of us only once in lifetime. 

DON'T FORGET TO USE SUNGLASSES WHILE LOOKING AT A Solar Eclipse

It is quite remarkable that the total Eclipse occurs at all. The Sun whose size 400 times larger than that of the Moon, happens to be about 400 times as far away from the earth. This condition permits just barely cover up the Sun. In fact, if the Moon's diameter (2,160 miles or 3,476 Kilometers) were just 140 miles (224 Kilometers) shorter than this, it could have never caused the total Solar Eclipse.

When Does It Occur?
For a Solar Eclipse to occur, the New Moon must be close enough to the ecliptic plane so that its shadow can touch at least some parts of the earth.  When the New Moon appears within 18-3/4 days before or after the alignment of a node (nodes are the two points where the Moon's orbit intersects the plane of the Earth's orbit) a Solar Eclipse will take place. This creates a 37-1/2 day time gap for Eclipses when the conditions are favorable for an Eclipse to occur.

If the Lunar nodes are stationary with respect to the stars, each node would be lined up between the earth and the Sun at the same time each year, the Eclipses would have occurred at the same time each year - every six month. But this is not so, because the nodes of the Lunar orbits shift their orientation gradually. Since the Moon's orbit is tilted 5 degree from the earth's orbit, normally it passes either below or above the line between the Sun and the earth. It is only about every 6 months the conditions are favorable for any Eclipse.

This alignment happens 18.6 days sooner than if the nodes have not been shifting, creating the shorter Eclipse year (normal Eclipse year = 346.6 days). This phenomenon determines the pattern of Eclipses. This change makes it happen earlier and earlier than before.

How Often It Occurs?
The repetition of Eclipses follows a very regular pattern in time. Partial phases of Solar Eclipse can be seen about every 2-1/2 years from any particular spot on the earth. The best estimate for total Eclipses is that they recur at the same location about every 360 years on the average. But sometimes this average varies widely, for example, London has never seen total Eclipse for 837 years (878 to 1715); while Angola coast witnessed almost 5 minutes total Eclipse on June 21, 2001, and then on December 4, 2002 for 2 minutes.

There will be 18 Solar Eclipses between 1996 and 2020. The common perception that the Eclipses are infrequent is because the observation of a total Eclipse from a given point of the earth is not common, for example, it will be two decades before the next total Solar Eclipse will be visible in North America. The last total Solar Eclipse was on August 11, 1999.

Total Solar Eclipses in India
(1)  1758, Dec 30    Annular Solar Eclipse in the Middle of India
(2)  1814, Jul 27     Total Solar Eclipse in Kashmeer   -    after 55.6 years
(3)  1868, Aug 18     Total Solar Eclipse in the Middle of India   -   after 65 years
(4)  1933, Aug 21     Annular Eclipse in North of India
(5)  1944, Jul 20     Annular Eclipse in South of India   -   after 55 years
(6)  1999, Aug 11     Total Solar Eclipse on Tropics of Cancer   -    after 131 years from the last Total Eclipse (1868)
(7)  2009, Jul 22    Total Solar Eclipse on Tropic of Cancer   -   after 10 years from the last Total Eclipse (1999)
(8)  2070, Apr 11    Total Solar Eclipse   
(9)  2074, Jan 27   Annular Solar Eclipse

(10) 2114, Jul 3      Total Solar Eclipse in North India   -   after nearly 105 years from the last Total Eclipse (2009)
(11)  2201, Sep 28   Total Solar Eclipse in South India

Patterns of Solar Eclipses
Two different cycles of the Moon determine the pattern of Eclipses over time.
One cycle -- the familiar monthly Lunar phases -- It is easy to understand: a Solar Eclipse may occur only at a New Moon, as the Moon passes between the Earth and the Sun, casting its shadow toward the Earth.
The other cycle involves the gradual shift in orientation of the Moon's orbit. Only when these two cycles are favorably combined (about every six months) can a Solar Eclipse occur.

We have a new Moon every month, but we donít have an Eclipse every month. Usually the Moon's shadow passes completely above or completely below the Earth. This is because the Moon's orbit is tilted at about a 5-degree angle to the Earth's orbit, so that the Moon usually passes above or below the direct line of sight between the Earth and the Sun.

Only at those times when the New Moon is near one of its nodes can a Solar Eclipse occur. (The nodes are the two points where the Moonís orbit intersects the plane of the Earthís orbit, the ecliptic). For a Solar Eclipse to occur, the new Moon must be close enough to the ecliptic plane so that itís shadow will touch some part of the Earth. As it turns out, when the New Moon appears within 18-3/4 days before or after the alignment of a node, a Solar Eclipse will take place. This creates a 37-1/2-day time window for Eclipse, called an Eclipse season, when the conditions are favorable for an Eclipse to occur.

If the Lunar nodes were stationary with respect to the stars, each node would be lined up between the Earth and the Sun at the same time each year, and Eclipses would occur at the same two periods of time, every year, six months apart. In fact, this is what almost happens, except that the nodes of the lunar orbit are gradually shifting their orientation in space. By the time one node is in line with the Sun again, it has regressed slightly. The alignment happens 18.6 days sooner than if the nodes were not moving, creating the shorter Eclipse year (about 346.6 days). This regular regression of the Moonís nodes is the other cycle that determines the patterns of Eclipses over time.
The result is that the Eclipse seasons gradually shift earlier and earlier each year, with a Solar Eclipse at a new Moon that falls within the window. The Solar Eclipse on March 9, 1997, is followed by successive Eclipses in the same season on Feb. 26, 1998 (total), Feb. 16, 1999 (annular), and Feb. 5, 2000 (partial).

These two cycles Ė the Lunar month (or Synodic month) and the Eclipse year Ė plod along year after year without much apparent coincidence. An Eclipse year (346.62 days) does not come close to being an exact multiple of these periods (324.83 days in 11 Synodic months, 354.36 in 12). A longer cycle, close to an exact multiple of these two periods, would be useful for making Eclipse predictions.
Just such a longer cycle, called the Saros cycle, was discovered by Babylonian astronomers in ancient times. The Saros (means repetition) lasts exactly 223 Synodic months. That's a period of 18 years 11-1/3 days (or 18 years 10-1/3 days if five February 29ths fall within the period). And the Saros coincides closely with 19 Eclipse years:
223 Synodic months (29.5306 days) = 6,585.32 days
19 Eclipse years (346.6200 days) = 6,585.78 days

This resonance between the periods of these two cycles produces a repetition of Eclipses in a remarkably short time. (In terms of astronomical cycles, 18 years is a short time) The paths of totality for successive Eclipses in this Saros series change in a regular pattern every 18 years. The paths, which are similar in shape, gradually widen and shift to more northerly latitudes. The longitude for each successive Eclipse in the series shifts to the west a little more than one third of the way around the globe.

A series of Eclipses, each separated by this 18-year 11-1/3-day cycle, is called a Saros series. Because the resonance between 19 Eclipse years and the Saros is not exact (0.46-day difference), a Saros series cannot go on indefinitely. Eventually a series reaches a point when the Eclipses are no longer visible; the umbra passes too far above or below the Earth to be seen. A single Saros series spans over 1,200 years and includes between 68 and 75 Solar Eclipses.

The repetition of Eclipses follows very regular patterns in time. Eclipse seasons and Saros cycles come and go like clockwork. The repetition of Eclipses at a given place on the Earth, however, appears to follow no discernible cycle. Partial phases of Solar Eclipses can be seen about every 2-1/2 years from any particular spot on the Earth. The best estimate for total Eclipses is to say they recur at the same location about every 360 years on the average. This figure is based on the average area of the paths of totality, the total surface area of the Earth, and the overall frequency of total Eclipses. But because we are dealing with averages over the time span of many millennia, the actual circumstances for particular locales vary, sometimes widely, from this estimate. For example, the Moonís umbra never passed over the city of London during a period of 837 years between consecutive total Solar Eclipses in the years 878 and 1715. On the other hand, if you visit the coast of Angola in southern Africa to witness almost 5 minutes of a total Eclipse on June 21, 2001, you can return to the same spot three Eclipse seasons later for two minutes of totality on Dec. 4, 2002.

 

 

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Created by Sushma Gupta on January 15, 2002
Contact:  sushmajee@yahoo.com
Modified on 09/23/13