Eclipses

Introduction to eclipse

• "Eclipse" is an astronomical event in which heavenly bodies (stars, planets, satellites, asteroids, comets, etc) are positioned such that one either heavenly body falls in the region of the shadow of another heavenly body, thereby making it invisible temporarily, or one heavenly body comes in between two heavenly bodies such that one is invisible to the other temporarily.
• The term "eclipse" is derived from the Greek word ékleipsis, which means "to cease to exist".
• An eclipse can be a complete eclipse or a partial eclipse. In the former, the heavenly body is hidden completely from view, whereas in the latter, the heavenly body is hidden from view partially.
• Eclipses can occur on any heavenly body like the sun, moon, earth, planets, etc.
• From earth we are able to observe two types of eclipses, the solar eclipses (i.e., the eclipses of the sun) and the lunar eclipses (i.e., the eclipses of the moon).

Solar Eclispe

 Introduction
A solar eclipse is an astronomical event in which observers at particular regions of the earth are unable to view the complete sphere of the sun due to the shadow of the moon falling on those regions of the earth. To the solar eclipse observers, the sun appears hidden from view partially or completely by the moon.

Position of the earth, moon and sun during a solar eclipse

A solar eclipse occurs only on a new moon day. The earth, sun and moon lie in the same straight line on a new moon day, with the moon in between the earth and the sun. Since sun is a luminous body, the moon's shadow is cast on the earth on a new moon day when the moon is close enough to the earth. Since the moon is smaller than the earth, the moon's shadow only falls on a small region on the earth, where the sun becomes hidden for the observers.

Partial and total solar eclipse

A partial solar eclipse is one in which the sun is not completely hidden from view by the moon. A total solar eclipse is one in which the sun is completely hidden from view by the moon.
There are two regions of the shadow of the moon falling on the earth during a solar eclipse. One is the Umbra, which is the region of complete darkness, and the other is the Penumbra, which is the region of semi-darkness.
Thus, during a solar eclipse, the region of the earth under the Umbra views a total solar eclipse, whereas the region of the earth under the penumbra views a partial solar eclipse.

Lunar Eclipse

Lunar eclipse introduction

A lunar eclipse is an astronomical event in which the moon is partially or completely hidden from view of the observers on the earth due to the shadow of the earth falling on the moon. A lunar eclipse occurs only on a full moon night, since relative position of the earth sun and moon are ideal for a lunar eclipse during a full moon night.

Position of the earth, sun and moon during a lunar eclipse

The earth, sun and moon are positioned in the same straight line during a lunar eclipse, with the earth in between the sun and the moon. A lunar eclipse takes place only when the shadow of the earth falls on the moon which causes the moon to be hidden from view as it is a non-luminous body, and can only be seen when it reflects the light of the sun.
A Lunar eclipse occurs when on a full moon night, the moon is close enough to the earth for the earth's shadow to fall on it. Furthermore, the moon has to be positioned in one of the nodes of its orbit around the earth for the shadow of the earth to fall on it.

Partial and total lunar eclipse

During a lunar eclipse, the moon passes into the region of the earth's shadow in space, and is thus rendered invisible for the time until it comes out of the earth's shadow as it orbits around the earth.
Thus, when the moon is completely inside the earth's shadow, it is completely hidden from view and forms a total lunar eclipse, whereas when it is partially hidden by the earth's shadow, it is said to be a partial lunar eclipse.