What is an eclipse?
An eclipse is one of the most appealing astronomical events that we could ever experience. The beauty of eclipses is that we can watch them without any expensive gadgets. This makes them more popular than any other astronomical events. An eclipse, in simple words, is a play of shadows. For an eclipse to occur, there should be three celestial bodies, of which one should be a light source because without a light source there won’t be any shadows. The Sun, the Earth, and the Moon should be aligned in a straight line or in a partially straight line for an eclipse to happen. The alignment of these three bodies in a straight line is called a syzygy.
An eclipse occurs when the light from the Sun is blocked by a planet or a moon and its shadow falls on the third celestial body. The moon and the earth cast three types of shadows: umbra, penumbra, and antumbra. Umbra is the darkest centre part of the shadow. Penumbra is the lighter outer region of the shadow. Antumbra is also a very light shadow which forms at the end of the umbral shadow. Thus, it only forms at a specific distance from the body that casts the shadow. Now let’s see how many types of eclipses are there. There are two types of eclipses. They are Solar eclipse and Lunar eclipse.
What is a Solar eclipse?
In a solar eclipse, the sun’s light gets blocked by the moon and it casts its shadow on the earth’s surface. The sun is 400 times bigger than the moon, but the distance from the Earth to the Sun is 400 times longer than the distance from the Earth to the Moon. So, the Moon and the Sun look the same size in the earth’s sky. A solar eclipse occurs only during a new moon. A new moon is a phase when the part of the Moon which we can see is dark and the opposite side of the moon will be lit by the sun.
A new moon occurs once in every 29½ days but an eclipse does not occur every 29½ days because the moon’s orbital plane is a few degrees tilted when compared to the earth’s orbital plane. The earth’s orbital plane is also called the ecliptic plane. An eclipse occurs, only when the moon is at the point in which the earth’s orbital plane or the ecliptic plane meets the moon’s orbital plane. This point is called a lunar node.
What are the types of Solar Eclipses?
There are 4 types of Solar Eclipses. They are :
1) Partial Solar eclipse
2) Annular Solar eclipse
3) Total Solar eclipse
4) Hybrid Solar eclipse
What is a Partial Solar Eclipse?
During a Partial Solar eclipse, the Sun’s light gets blocked by the Moon and the Moon’s penumbral shadow falls on the earth. An observer viewing from the penumbral shadow region of the earth can observe a partial solar eclipse. When a partial solar eclipse is from the Earth, it would look like someone bit a small piece from the Sun.
What is an Annular Solar Eclipse?
During an annular solar eclipse, the Sun’s light gets blocked by the Moon. But here, the distance between the earth and the moon is longer. The umbral part of the Moon’s shadow ends before falling on the Earth thus surface of the Earth covers only the antumbral part. An observer viewing from the antumbral shadow region of the earth can observe an Annular Solar eclipse. During this eclipse, we can see that the moon cannot completely cover the entire disk of the sun. A thin outer ring of the sun will be visible. This ring is called ‘The Ring of Fire’ or the ‘Annulus’. This is a dramatic and beautiful event which takes place during an Annular solar eclipse.
What is a Total Solar Eclipse?
During a Total Solar eclipse, the sun’s light gets blocked by the moon and the moon’s umbral shadow falls on the earth. An observer viewing from the umbral shadow region of the earth can observe a total solar eclipse. This is the rarest of all solar eclipses. During the totality i.e when the moon completely blocks the sun, we can observe a gas cloud like thing surrounding the moon. It is known as the Corona. The Corona is the outer atmosphere of the sun. We cannot see this during a normal day with a telescope and sun filter. The corona is just the outer atmosphere of the sun, so instead of emitting any light it reflects the light from the sun. The most dramatic views that can be observed during the Total Solar eclipse are the corona, the bailey’s beads and the diamond ring effect.
What is a Hybrid Solar eclipse?
During a Hybrid Solar Eclipse, the Sun’s light gets blocked by the Moon, and the Earth is in the place where the umbral shadow and the antumbral shadow meet i.e the point in which the umbral shadow ends and the antumbral shadow begins. Due to the curvature of the Earth, the distance between the Moon and the Earth’s surface varies in different places. While in some parts of the Earth the antumbral shadow falls, in other parts it is penumbral and umbral shadow which hits the Earth.
So all types of eclipses happen in different parts of the earth. Hybrid Solar Eclipse is the rarest of all eclipses. The last Hybrid Solar Eclipse was in 2013 and the next Hybrid Solar Eclipse will happen only in 2023.
What will happen if we view a Solar Eclipse with naked eyes?
While watching a Solar Eclipse we must always obey the safety precautions. Taking a walk during a solar eclipse is much safer than doing the same during an ordinary day. Because during a normal day, the sun emits Ultraviolet Rays, Infrared Rays, X-rays, etc. During a total solar eclipse, more than 95% of the light emitted by the Sun including the harmful Rays are blocked by the Moon. So, less harmful rays reach the surface of the Earth. But it is not the same case while watching a Solar Eclipse with naked eyes. There is a part of our eye called pupil, which is a small opening that shrinks and expands according to the light condition. When you are in a bright light condition, our pupil shrinks because if bright light hits our retina directly, then it can damage it.
When the pupil shrinks, the amount of light reaching the retina will decrease. When we are in a low light condition, our pupils will expand because very less light is reaching the retina. When the pupils expand, more light will reach the retina thus getting a much clearer image. During a total solar eclipse, at the time of totality, it is safe to view the eclipse with naked eyes. Here it is a low light condition, so our pupils will be wide open. But, it only takes a fraction of a second for the moon to move away from the sun’s disk. At this time our retina senses the bright light and sends a signal to the pupil to shrink. But before the pupil completely shrinks, the bright harmful rays will reach the retina. This can cause serious damage to the eyes and can even lead to permanent eye blindness.
How can we view a solar eclipse safely?
Never try watching a solar eclipse with naked eyes. If we are viewing with naked eyes, we have to use a quality solar filter or quality eclipse glasses which are available in the market. They are equipped with quality solar filters and are very cheap and easy to use. If we are observing the solar eclipse with a telescope, binoculars or a monocular, we can use quality solar filters which are available in the market. We can attach this filter on the opening through which light enters the optical instrument or you can use indirect viewing methods like the projector method.
In this method, you have to align the optical instrument directly at the sun. Do not align it by directly looking at the sun through the eyepiece or viewfinder. What we have to do is, try aligning the instrument by using the shadows. When the shadows are the sharpest, your optical instrument is aligned perfectly with the sun. If you are using binoculars or a monocular, take a white piece of paper and hold it at an average of fifteen centimetres to a few metres. It depends on the focusing range of your instrument. You can see a projected image of the sun in the paper. If you are using a telescope, you have to remove the eyepiece or if you have a Barlow lens 2x or 3x or any Barlow lens, then use that as your eyepiece. Take a piece of paper and place it a few metres away. You can change the size of the projected image by changing the distance between the eyepiece of the telescope and the piece of paper. For focusing the image, use the focus ring in the eyepiece holder.
We can also watch a solar eclipse using a simple pinhole projector method. For this method, you need 2 sheets of white paper. First, take one sheet of paper and put a pinhole in it. Hold this paper directly at the sun. While aligning, do not look directly at the sun. Always use the shadow method which I have mentioned earlier. Then, take the second piece of paper and hold it behind the pin holed paper so that the sunlight can be projected through the pinhole and on to the paper. While using this method do not ever look at the sun directly through the pinhole. By adjusting the distance between the pin holed paper and the other piece of paper, you can focus the projected image.
What is Lunar Eclipse?
A Lunar Eclipse occurs when the Earth blocks the sunlight from reaching the Moon. It only occurs during a full moon night. But it does not occur every full moon because of the Lunar Nodes, about which I have mentioned earlier. A Full moon is a phase of the Moon when the side which we can see is lit by the Sun and the opposite side would be dark. During a total lunar eclipse, the Earth completely blocks the sunlight from reaching the Moon. But the phase of the Moon does not go completely dark. It is because of the Earth’s atmosphere. We will discuss it later. Unlike the solar eclipse, a lunar eclipse can be viewed by anyone on the night side of the Earth because the Earth is the one who is casting the shadows.
Types of Lunar Eclipses
- Total Lunar Eclipse
- Partial Lunar Eclipse
- Penumbral Lunar Eclipse
What is a Total Lunar Eclipse?
A Total Lunar Eclipse occurs when the Earth completely blocks all the sunlight from reaching the Moon and the Moon falls into the umbral shadow cast by the Earth. But due to the scattering of light in the Earth’s atmosphere, the Moon looks red in colour. During a Total Lunar Eclipse, if you are standing on the Moon, you can see that the Earth is completely blocking the Sun like a solar eclipse. This eclipse can be viewed from any one standing on the night side of the Earth.
What is a Partial Lunar Eclipse?
During a Partial Lunar Eclipse, the Earth partially blocks the sunlight from reaching the Moon. So the umbral shadow covers some portion of the Moon and the penumbral shadow covers the rest. The part of the Moon which is covered by the umbral shadow will look red in colour and the part of the Moon which is covered by the penumbral shadow will look a little dimmer than a normal full moon. This eclipse can also be observed by any one from the night side of the Earth.
What is a Penumbral Lunar Eclipse?
During a penumbral lunar eclipse, the Earth’s penumbral shadow will completely cover the surface of the Moon. Since the Earth’s penumbral shadow is covering the entire surface of the Moon, this kind of eclipse is called a penumbral lunar eclipse. During this penumbral lunar eclipse, the Moon’s surface will not appear red in colour, because the umbral shadow, which gives the red tint, is not covering the Moon’s surface. During this type of eclipse, most of the people get confused whether this is an eclipse or a normal full moon. This is because, during a penumbral lunar eclipse, the Moon only gets a little dimmer than a normal full moon.
Blood moon
We all must have wondered why the Moon looks red during a Total Lunar Eclipse and a Partial Lunar Eclipse. So, let’s find out why. Red light has a lower frequency and a higher wavelength. The blue light, on the other hand, has a higher frequency and a lower wavelength. This means that blue light has more energy than red light. Energy decreases when the frequency decreases.
The Sun emits all colours of light. When blue light enters the atmosphere of the Earth, due to its short wavelength, it gets completely scattered and due to this, very less blue light hits the surface of the Earth. But when red light reaches the atmosphere, due to its very high wavelength, very little scattering happens. So, the red light can reach the surface of the Earth and can reflect off from the surface and reach the Moon. This phenomenon is called Rayleigh’s Scattering of light. This is why the Moon looks red during a Total Lunar Eclipse and a Partial Lunar Eclipse. It is the same reason why our sky looks blue in the morning.
Superstitions connected with Solar Eclipse
There are so many superstitions connected with the Solar Eclipse. Actually, these superstitions have nothing to do with the them. Such stories arose from sheer fear and curiosity connected with the myths and legends throughout history. At the present day, with the technology we have developed, we can predict the eclipses accurately in seconds and even visualize how an eclipse will occur 1000 years later. Unfortunately, even today, an eclipse of the Sun is considered a bad omen in many cultures. When the Sun vanishes temporarily during an eclipse, people believe their fearsome demon has eaten the Sun.
The ancient people believed that mythical creatures were trying to eat the Sun or to steal the Sun. They threw stones at the sky to scare the demons away to save the Sun. When the eclipse is over and the Sun came out again, they believed that throwing stones scared the demons away. In Vietnam, instead of a demon, a giant frog tries to eat the Sun, in ancient China, a celestial dragon; in ancient Hindu mythology, deity Rahu; in Korea, mythical dogs; in America, a giant bear and the story goes on. These man-made stories have nothing to do with a solar eclipse. A solar eclipse is a beautiful and rare astronomical event which rarely takes place. The only precaution we have to take while observing it is using a quality solar filter or using the techniques I mentioned above.
My experience of viewing a Solar eclipse
I am from Trivandrum which is a small District in the southern State of Kerala, India. During the Annular Solar eclipse which occurred on December 26, 2019, last year, my place could witness only a partial solar eclipse. So my father and I travelled around 400 km to Malappuram District with tripod, cameras etc. The sky was a bit cloudy and I was a bit scared, but at the time of annularity, a window in the sky opened. I took around 1500 photos using my Sony A 6000 camera and 70 -350 mm lens and the magnificent view which I cannot forget in my lifetime. I cannot describe it in words. What I saw was a sparkling gold bangle. So say bye to superstitions and don’t miss a solar eclipse because it is worth a view. I am sharing some pictures which I took when I witnessed the celestial beauty.
-Arjun Sooraj
Here is another article written By Arjun Sooraj- The Evolution of Stars
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