Soorya Grahana

A solar eclipse occurs when the moon passes between the Sun and the Earth so that the Sun is fully or partially covered. This can only happen during a new moon, when the Sun and Moon are in conjunction as seen from the Earth. At least two and up to five solar eclipses can occur each year on Earth, with between zero and two of them being total eclipses.[1][2] Total solar eclipses are nevertheless rare at any location because during each eclipse totality exists only along a narrow corridor in the relatively tiny area of the Moon's umbra.

A total solar eclipse is a spectacular natural phenomenon and many people travel to remote locations to observe one. The solar eclipse of August 11, 1999 in Europe helped to increase public awareness of the phenomenon, as illustrated by the number of journeys made specifically to witness the total solar eclipse of October 3, 2005 and the total solar eclipse of March 29, 2006. The recent solar eclipse of January 26, 2009, was an annular eclipse (see below), while the solar eclipse of July 22, 2009 was a total solar eclipse.

The next annular event is the Solar eclipse of January 15, 2010 and the next total event is the solar eclipse of July 11, 2010.

In ancient times, and in some cultures today, solar eclipses have been attributed to supernatural causes. Total solar eclipses can be frightening for people who are unaware of their astronomical explanation, as the Sun seems to disappear in the middle of the day and the sky darkens in a matter of minutes.

There are four types of solar eclipses:

A total eclipse occurs when the Sun is completely obscured by the Moon. The intensely bright disk of the Sun is replaced by the dark silhouette of the Moon, and the much fainter corona is visible. During any one eclipse, totality is visible only from at most a narrow track on the surface of the Earth.
An annular eclipse occurs when the Sun and Moon are exactly in line, but the apparent size of the Moon is smaller than that of the Sun. Hence the Sun appears as a very bright ring, or annulus, surrounding the outline of the Moon.
A hybrid eclipse (also called annular/total eclipse) transitions between a total and annular eclipse. At some points on the surface of the Earth it is visible as a total eclipse, whereas at others it is annular. Hybrid eclipses are comparatively rare.
A partial eclipse occurs when the Sun and Moon are not exactly in line and the Moon only partially obscures the Sun. This phenomenon can usually be seen from a large part of the Earth outside of the track of an annular or total eclipse. However, some eclipses can only be seen as a partial eclipse, because the umbra never intersects the Earth's surface, passing above the Earth's polar regions.
The Sun's distance from the Earth is about 390 times the Moon's distance, and the Sun's diameter is about 400 times the Moon's diameter. Because these ratios are approximately the same, the Sun and the Moon as seen from Earth appear to be approximately the same size: about 0.5 degree of arc in angular measure.

The Moon's orbit around the Earth is an ellipse, as is the Earth's orbit around the Sun; the apparent sizes of the Sun and Moon therefore vary.[4][5] The magnitude of an eclipse is the ratio of the apparent size of the Moon to the apparent size of the Sun during an eclipse. An eclipse when the Moon is near its closest distance from the Earth (i.e., near its perigee) can be a total eclipse because the Moon will appear to be large enough to cover completely the Sun's bright disk, or photosphere; a total eclipse has a magnitude greater than 1. Conversely, an eclipse when the Moon is near its farthest distance from the Earth (i.e., near its apogee) can only be an annular eclipse because the Moon will appear to be slightly smaller than the Sun; the magnitude of an annular eclipse is less than 1. Slightly more solar eclipses are annular than total because, on average, the Moon lies too far from Earth to cover the Sun completely. A hybrid eclipse occurs when the magnitude of an eclipse transitions during the event from smaller than one to larger than one—or vice versa—so the eclipse appears to be total at some locations on Earth and annular at other locations.[6]

The Earth's orbit around the Sun is also elliptical, so the Earth's distance from the Sun varies throughout the year. This also affects the apparent sizes of the Sun and Moon, but not so much as the Moon's varying distance from the Earth. When the Earth approaches its farthest distance from the Sun (the aphelion) in July, this tends to favor a total eclipse. As the Earth approaches its closest distance from the Sun (the perihelion) in January, this tends to favor an annular eclipse.

Central eclipse is often used as a generic term for a total, annular, or hybrid eclipse. This is, however, not completely correct: the definition of a central eclipse is an eclipse during which the central line of the umbra touches the Earth's surface. It is possible, though extremely rare, that part of the umbra intersects with Earth (thus creating an annular or total eclipse), but not its central line. This is then called a non-central total or annular eclipse.[7] The next non-central solar eclipse will be on April 29, 2014. This will be an annular eclipse. The next non-central total solar eclipse will be on April 9, 2043.[8]

The phases observed during a total eclipse are called:

First Contact - when the moon's shadow first becomes visible on the solar disk. Some also name individual phases between First and Second Contact e.g. Pac-Man phase.
Second Contact - starting with Baily's Beads {cause by light shining through valleys on the moon's surface} and the Diamond Ring. Almost the entire disk is covered.
Totality - with the shadow of the moon obscuring the entire disk of the sun and only the corona visible
Third Contact - when the first bright light becomes visible and the shadow is moving away from the sun. Again a Diamond Ring may be observed

Historical eclipses are a valuable resource for historians, in that they allow a few historical events to be precisely dated, from which other dates and a society's calendar can be deduced. Aryabhata (476–550) concluded the Heliocentric theory in solar eclipse. A solar eclipse of June 15, 763 BCE mentioned in an Assyrian text is important for the Chronology of the Ancient Orient. Also known as the eclipse of Bur Sagale, it is the earliest solar eclipse mentioned in historical sources that has been successfully identified. Perhaps the earliest still-unproven claim is that of archaeologist Bruce Masse; on the basis of several ancient flood myths that mention a total solar eclipse, he links an eclipse that occurred May 10, 2807 BCE with a possible meteor impact in the Indian Ocean.[20] There have been other claims to date earlier eclipses, notably that of Mursili II (likely 1312 BCE), in Babylonia, and also in China, during the 5th year (2084 BCE) of the regime of Emperor Zhong Kang of Xia dynasty, but these are highly disputed and rely on much supposition.[21][22]

Herodotus wrote that Thales of Miletus predicted an eclipse which occurred during a war between the Medians and the Lydians. Soldiers on both sides put down their weapons and declared peace as a result of the eclipse. Exactly which eclipse was involved has remained uncertain, although the issue has been studied by hundreds of ancient and modern authorities. One likely candidate took place on May 28, 585 BCE, probably near the Halys river in the middle of modern Turkey.[23]

An annular eclipse of the Sun occurred at Sardis on February 17, 478 BCE, while Xerxes was departing for his expedition against Greece, as Herodotus recorded.[24] Hind and Chambers considered this absolute date more than a century ago.[25] Herodotus also reports that another solar eclipse was observed in Sparta during the next year, on August 1, 477 BCE.[26][27][28] The sky suddenly darkened in the middle of the day, well after the battles of Thermopylae and Salamis, after the departure of Mardonius to Thessaly at the beginning of the spring of (477 BCE) and his second attack on Athens, after the return of Cleombrotus to Sparta. The modern conventional dates are different by a year or two, and that these two eclipse records have been ignored so far.[29] The Chronicle of Ireland recorded a solar eclipse on June 29, 512 CE, and a solar eclipse was reported to have taken place during the Battle of Stiklestad in July, 1030.

It has also been attempted to establish the exact date of Good Friday by means of solar eclipses, but this research has not yielded conclusive results.[30] Research has manifested the inability of total solar eclipses to serve as explanations for the recorded Good Friday features of the crucifixion eclipse.[31] (Good Friday is recorded as being at Passover, which is also recorded as being at or near the time of a full moon.)

The ancient Chinese astronomer Shi Shen (fl. 4th century BCE) was aware of the relation of the moon in a solar eclipse, as he provided instructions in his writing to predict them by using the relative positions of the moon and sun.[32] The 'radiating influence' theory for a solar eclipse (i.e., the moon's light was merely light reflected from the sun) was existent in Chinese thought from about the 6th century BCE (in the Zhi Ran of Zhi Ni Zi),[33] and opposed by the Chinese philosopher Wang Chong (27–97 CE), who made clear in his writing that this theory was nothing new.