‘Solar’ means Sun and ‘Eclipse’ means obscuration of the light from a celestial body by another. In simpler terms, Solar Eclipse happens when the moon comes in front of the sun and hence obstructs the light coming from the sun. The Sun is being eclipsed by the moon and the moon casts its shadow on the Earth henceforth, we have a Solar Eclipse.
We have always heard that solar eclipse is a rare celestial phenomenon, but why?
There are three main reasons for this -
Firstly every month, the moon comes in between Sun and the Earth, so we must have Solar Eclipse 12 times a year. Right? Let me explain this to you with the fact that Moon is tilted at 5 degrees, just how our earth is tilted at 23.5 degrees. We all know that for a solar eclipse to happen all three celestial body i.e. Sun, Moon, and Earth must be aligned in a straight line respectively. On average we can witness two of them from Earth in a year (At least once a year and at max 5 – very very rare, the last time it happened in 1935 and the next time it will be in the year 2206).
The second big factor is your location. It’s estimated that any one spot on Earth sees a total Solar Eclipse once in 360 years. Now, why so? Because a particular Solar Eclipse is only visible from a narrow path across the globe; for Total Solar Eclipse – the path of totality. The width of the shadow in Total/Annular Solar Eclipse is 100-160Km wide. Again, my question is- why?
For better understanding, let’s take the example of lunar eclipses. Have you noticed, we are more likely to see lunar Eclipse rather than a Solar Eclipse though the frequency with both the celestial event happens is the same? This happens because, at the time of the lunar eclipse, the Earth casts its shadow on the whole lunar surface this happens because the Earth is bigger in size. So, lunar eclipses are more widely visible. Talking about the Solar Eclipse, the moon’s shadow on the Earth is not very big therefore, only a small portion of the Earth Surface is covered – the narrow path as shown below for the worldwide Solar Eclipses for this decade.
Third key point is that what type of eclipse, you would be witnessing. There are four main types of Solar Eclipses as follows, but before going into the types of Eclipses, let’s have brief look at the 2 parts of the shadow that are cast by the moon. Penumbra – The moon’s big and faint outer shadow. Partial solar eclipses are visible from the regions under Penumbral shadow. The other is Umbra – The moon’s small and darker inner shadow which causes a remarkable Total/Annular Solar Eclipse. The type of Eclipse depends upon the part of the moon’s shadow we are in.
Total Solar Eclipse – It happens when the moon covers the Sun completely and hence blocks all the light coming from the Sun. The narrow path followed by the eclipse across the globe is known as the path of totality and is visible form only 1 % of the Earth's Surface. Totality may be visible for as max as 7 minutes 31 seconds, mostly all of them are of shorter durations. Total Solar Eclipse is very important to the Astronomers and the Scientific Community. This is the only time when they can capture the outer layer of the sun i.e. Coronal mass ejections and study it carefully.
“It is considered to be one of the most awe-inspiring spectacles in all of nature. The sky takes on an eerie twilight as the Sun's bright face is replaced by the black disk of the Moon. Surrounding the Moon is a beautiful gossamer halo. This is the Sun's spectacular Solar Corona, a super-heated plasma two million degrees in temperature. The corona can only be seen during the few brief minutes of totality. To witness such an event is a singularly memorable experience which cannot be conveyed adequately through words or photographs – Mr. Eclipse”
Can you imagine that there will be a day from when on Earthlings won’t be able to see the Total Solar Eclipse because of the lunar retreat - as we all know the moon is moving away by 20.8 cm each year? So there will be a time when the people on the Earth would never be able to see Total Solar Eclipse but only the Annular Solar Eclipse. What? How? And Why?
Annular Solar Eclipse – Annular Solar Eclipses are awe-inspiring celestial events and people all over the world love to capture this moment. Wait, Annular doesn’t mean Annual but Annular mean a Ring and hence this eclipse is known as a Ring of Fire.
We see a ring of fire as the moon orbits our planet in an elliptical path. Therefore there is a 13% variation in the apparent size of the moon. If the moon is near its Perigee then the moon’s apparent size is bigger and hence it could eclipse the whole Sun but when the moon is near its Apogee, its apparent size is small and hence it can’t cover up the whole Sun, resulting in a ring of fire whose width is directly dependent upon how far the moon is from the Earth.
In short, now try to visualize this, “The sun’s diameter is about 400 times larger than that of the moon – and the sun is also about 400 times farther from the Earth. So the Sun and the moon appears nearly the same size as seen from the Earth.”
Let us come back to the question we started off with, why is this celestial event so rare?
For India, this is our last chance for the decade, so make sure that you grab the opportunity and look up to the sun with SAFE METHODS – Solar view goggles, Solar Filter, Pinhole projector, etc. but not at all directly with unaided eyes or X-rays.
Next Solar Eclipse for India is happening in 2031, that too visible from the southern part of India (There is no eclipse happening in the meantime for India)
Details - 21 June 2020, Solstice Annular Solar Eclipse.
100% Visibility – a narrow path from Rajasthan, Punjab, Uttarakhand (Dehradun)
(Link- Eclipse Calculator is given below)
Partial Solar Eclipse is a self-defining term. When there is a penumbral shadow of the moon on the Earth, we observe a Partial Solar Eclipse.
Hybrid Solar Eclipse – Rarest of all. This oddball Eclipse is also known as Total/Annual Solar Eclipse. It changes its types as the moon’s shadow moves across the Earth. Therefore we would see both the eclipses.
“There is a very particular alignment because the moon is, of course, is not the same size as the sun. Rather, its apparent size when viewed from the Earth can be the same as the apparent size of the sun in the sky - to get that geometry lined up is a very special thing”
- The perfect size of the moon
- Perfect distance between the moon and the sun
So clear out this misconception from your mind that this celestial Phenomenon is a rare one to observe but yes the possibility that you see more than one Total Solar eclipse in a lifetime is rare.
And then comes the astrophotography to capture the magnificent Sun in its eclipse phase from a given location, as you can imagine that the probability of seeing the eclipse of the same type from the same place is really very rare; in fact impossible in a lifetime.
Get ready to witness the mesmerizing play of hide and seek between the moon and the Sun.
-Divyeshwari Vansadia :)
Worldwide Solar Eclipse info for this decade https://www.timeanddate.com/eclipse/list.html
Eclipse Calculator
Astrophotography tips & tricks by Fred Espenak, Mr. Eclipse - American astrophysicist
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