Eclipse is a astronomical phenomenon 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 is a derived from a greek word and
means "to abandon", "to darken"
We observe two types of eclipse:
SOLAR
ECLIPSE
As seen from the Earth, a solar eclipse
occurs when the Moon passes between the Sun and the Earth, and the Moon fully
or partially blocks the Sun. This can happen only during a new moon, when the
Sun and the Moon are in conjunction as seen from Earth.
LUNAR
ECLIPSE
A lunar eclipse occurs when the Moon
passes behind the Earth so 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, a lunar
eclipse can only occur the night of a full moon.
We will discuss both lunar and Solar
eclipse in a bit detail below.
UMBRA AND PENUMBRA:
If the light source
is a point, then all objects will have one kind of shadow behind them. But if
the light source is a sphere (like the sun), then every object has behind it a
core shadow called as the umbra and a sort of
side-way shadow called as the penumbra.
LUNAR
ECLIPSE:
Lunar eclipse occurs when earth is between
sun and the moon and earth’s shadow falls on the moon.
An eclipse of the Moon or lunar eclipse
can only occur
at Full Moon and only if the Moon passes through some portion of Earth's
shadow. That shadow is actually composed of two cone-shaped components, one
nested inside the other. The outer or penumbral shadow is a zone where the
Earth blocks part but not all of the Sun's rays from reaching the Moon. In
contrast, the inner or umbral shadow is a region where the Earth blocks all direct sunlight from
reaching the Moon.
There are three basic types of lunar
eclipse:
- Penumbral Lunar Eclipse
- Partial Lunar Eclipse
- A portion of the
Moon passes through Earth's umbrae shadow.
- These events are
easy to see, even with the naked eye.
- Total Lunar Eclipse
- The entire Moon
passes through umbra of the Earth’s shadow.
- These events are
quite striking due to the Moon's vibrant red colour during the total phase.
Total Lunar Eclipse is the most fascinating phenomenon as the moon
appears red and looks more beautiful.
But how do you know how this happens?
-It is because of the
air we breathe. If there would have been no atmosphere on the Earth then the moon
would have appeared black.
But because of the
atmosphere on the Earth the sunlight falling on earth gets scattered into its
respective constituent colours among which red light scatters the least and
falls on the moon.
SOLAR ECLIPSE:
Solar eclipse occurs when moon is in between sun and earth and moon’s shadow falls on the earth
An eclipse of the Sun (or solar eclipse)
can only occur
at New Moon when the Moon passes between Earth and Sun. If the Moon's shadow
happens to fall upon Earth's surface at that time, we see some portion of the
Sun's disk covered or 'eclipsed' by the Moon. Since New Moon occurs every 29
1/2 days, you might think that we should have a solar eclipse about once a
month. Unfortunately, this doesn't happen because the Moon's orbit around Earth
is tilted 5 degrees to Earth's orbit around the Sun. As a result, the Moon's
shadow usually misses Earth as it passes above or below our planet at New Moon.
At least twice a year, the geometry lines up just right so that some part of
the Moon's shadow falls on Earth's surface and an eclipse of the Sun is seen
from that region.
There are three types of solar eclipse:
- Partial Solar Eclipse
When the Moon's penumbral shadow strikes
Earth, we see a partial eclipse of the Sun from that region. Partial eclipses
are dangerous to look at because the un-eclipsed part of the Sun is still very
bright. You must use special filters or a home-made pinhole projector to safely
watch a partial eclipse of the Sun.
2. Total Solar Eclipse
If the Moon's inner or umbral shadow sweeps
across Earth's surface, then a total eclipse of the Sun is seen. The track of
the Moon's umbral shadow across Earth is called the Path of Totality. It is typically 10,000
miles long but only about 100 miles wide. It covers less than 1% of Earth's
entire surface area. In order to see the Sun become completely eclipsed by the
Moon, you must be somewhere inside the narrow path of totality. The path of a
total eclipse can cross any part of Earth.
- Annual Solar Eclipse
Sometimes Moon is not able to cover all the sun. If an eclipse occurs while the Moon is on the far side of its orbit, the Moon appears smaller than the Sun and can't completely cover it. Looking down from space, we would see that the Moon's umbral shadow is not long enough to reach Earth. Thus we see the annular solar eclipse. Annularity can last as long as a dozen minutes, but is more typically about half that length. Since the annular phase is so bright, the Sun's gorgeous corona remains hidden from view. But annular eclipses are still quite interesting to watch.
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Article
done by Akshay Nemande
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