Lunar and Solar Eclispe

DO YOU KNOW WHAT IS LUNAR AND SOLAR ECLISPE?

LUNAR ECLISPE

A lunar eclipse is an eclipse which occurs whenever the moon passes behind the earth such that the earth blocks the sun's rays from striking the moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, there is always a full moon the night of a lunar eclipse. The type and length of an eclipse depend upon the Moon's location relative to its orbital nodes.

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.

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.

A partial lunar eclipse occurs when only a portion of the Moon enters the umbra. When the Moon travels completely into the Earth¹s umbra, one observes a total lunar eclipse. The Moon's speed through the shadow is about one kilometer per second (2,300 mph), and totality may last up to nearly 107 minutes. Nevertheless, the total time between the Moon¹s first and last contact with the shadow is much longer, and could last up to 3.8 hours.

The relative distance of the Moon from the Earth at the time of an eclipse can affect the eclipse¹s duration. In particular, when the Moon is near its apogee, the farthest point from the Earth in its orbit, its orbital speed is the slowest. The diameter of the umbra does not decrease much with distance. Thus, a totally-eclipsed Moon occurring near apogee will lengthen the duration of totality.

SOLAR ECLISPE

A solar eclipse occurs when the Moon passes in front of the Sun and obscures it totally or partially. This configuration can only exist at New Moon, when Sun, Moon and Earth are on a single line with the Moon in the middle.

There are four types of solar eclipses:

• A partial solar eclipse occurs when the Sun is only partially overlapped by the Moon.
• A total solar eclipse occurs when the Moon completely obscures the Sun. This happens when the Moon is near perigee and its angular diameter as seen from Earth is identical to or slightly larger than that of the Sun. A total solar eclipse is the only opportunity to observe the Sun's corona without specialised equipment.
• An annular (ring-formed) eclipse occurs when the Moon's center passes in front of Sun's center while the Moon is near apogee. The Moon's angular diameter is then smaller than that of the Sun so that a ring of the Sun can still be seen around the Moon. This is similar to a penumbral eclipse.
• A hybrid eclipse occurs when the curvature of Earth's surface causes a single solar eclipse to be observed as annular from some locations but total from other locations. A total eclipse is seen from places on the Earth's surface that lie along the path of the eclipse and are physically closer to the Moon, and so intersect the Moon's umbra; other locations, further from the Moon, fall in the Moon's antumbra and the eclipse is annular.

The term "solar eclipse" is a misnomer: the phenomenon is actually an occultation. An "eclipse" occurs when one celestial object passes into the shadow cast by another (as with an eclipse of the Moon). An "occultation' occurs when one body passes in front of another. When at its new phase the Moon passes in front of, or occults, the Sun, as seen from Earth, the Moon also casts a small shadow on Earth. An "occultation" of the Sun is therefore also a partial "eclipse" of Earth.

Observing a solar eclipse

Looking at the Sun is dangerous at any time when any part of the brilliant visible disk of the Sun (its photosphere) is visible; to do so can cause permanent eye damage. This is true at any time, including during solar eclipses; since an eclipse offers an unusually high temptation to look at the Sun, there is a high incidence of eye damage caused during solar eclipses. Viewing the Sun through any kind of optical aid, binoculars, a telescope, or even a camera's viewfinder- is extremely dangerous.