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What is Eclipse?

An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer.

Eclipse cycles

An eclipse cycle takes place when a series of eclipses are separated by a certain interval of time. This happens when the orbital motions of the bodies form repeating harmonic patterns.

Earth-Moon System

1. An eclipse involving the Sun, Earth and Moon can occur only when they are nearly in a straight line, allowing one to be hidden behind another, viewed from the third.

2. The Sun, Earth and nodes are aligned twice a year(during an eclipse season), and eclipses can occur during a period of about two months around these times.

3. There can be from four to seven eclipses in a calendar year, which repeat according to various eclipse cycles.

Solar eclipse

As observed from the Earth, a solar eclipse occurs when the Moon passes in front of the Sun.

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The region of the Moon's shadow in a solar eclipse is divided into three parts:

  1. The umbra, within which the Moon completely covers the Sun (more precisely, its photosphere).
  2. The antumbra, extending beyond the tip of the umbra, within which the Moon is completely in front of the Sun but too small to completely cover it.
  3. The penumbra, within which the Moon is only partially in front of the Sun.

The type of solar eclipse event depends on the distance of the Moon from the Earth during the event.

There are four types of solar eclipses:

  1. A total eclipse occurs when the dark silhouette of the Moon completely obscures the intensely bright light of the Sun, allowing the much fainter solar corona to be visible.
  2. 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 dark disk of the Moon.
  3. A hybrid eclipse (also called annular/total eclipse) shifts between a total and annular eclipse. At certain points on the surface of Earth it appears as a total eclipse, whereas at other points it appears as annular. Hybrid eclipses are comparatively rare.
  4. 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 Earth outside of the track of an annular or total eclipse.

Solar eclipses can only be viewed in totality along a relatively narrow track, which at the maximum can last for 7 minutes, 31 seconds, and can be viewed along a track that is up to 250 km wide.

Partial eclipse can be observed is much wider track.

Lunar eclipse

A lunar eclipse occurs when the Moon passes directly behind the Earth into its umbra (shadow). 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 the night of a full moon.

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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. However, as a result of the Sun's large angular size, solar illumination is only partially blocked in the outer portion of the Earth's shadow, which is given the name penumbra.

The type and length of an eclipse depend upon the Moon's location relative to its orbital nodes.

There are three types of Lunar eclipses:

  1. Penumbral eclipse:

A penumbral eclipse occurs when the Moon passes through the Earth's penumbra. The penumbra causes a subtle darkening of the Moon's surface. A special type of penumbral eclipse is a total penumbral eclipse, during which the Moon lies exclusively within the Earth's penumbra. Total penumbral eclipses are rare, and when these occur, that portion of the Moon which is closest to the umbra can appear somewhat darker than the rest of the Moon.

  1. Partial Lunar eclipse:

A partial lunar eclipse occurs when only a portion of the Moon enters the umbra.

  1. Total lunar eclipse:

When the Moon travels completely into the Earth's umbra, one observes a total lunar eclipse.

Even during a total lunar eclipse, however, the Moon is not completely dark. Sunlight refracted through the Earth's atmosphere enters the umbra and provides a faint illumination. Much as in a sunset, the atmosphere tends to more strongly scatter light with shorter wavelengths, so the illumination of the Moon by refracted light has a red hue, thus the phrase 'Blood Moon' is often found in descriptions of such lunar events as far back as eclipses are recorded.

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.

Unlike solar eclipses, lunar eclipses are safe to view without any eye protection or special precautions, as they are dimmer than the full Moon.


1.On Mars, only partial solar eclipses (transits) are possible, because neither of its moons is large enough, at their respective orbital radii, to cover the Sun's disc as seen from the surface of the planet.

2. Eclipses of the moons by Mars are not only possible, but commonplace, with hundreds occurring each Earth year. There are also rare occasions when Deimos is eclipsed by Phobos.

3. Martian eclipses have been photographed from both the surface of Mars and from orbit.

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