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Eclipse is a natural occurrence. Eclipse is an astronomical phenomenon which occurs when one celestial object comes within the shadow of another spatial object. This usually hinders the observer from seeing one of them in space. There are two types of eclipses on Earth: Solar Eclipse and Lunar Eclipse.
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Key terms: Solar eclipse, Eclipse, Lunar eclipse, Sun, Moon, Earth, Penumbra, Total eclipse, Annual eclipse, Partial eclipse
What is Eclipse?
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Eclipse is an astronomical phenomenon that occurs when one spatial object passes through the shadow of another. In its orbit, the Earth revolves around the Sun like the other planets. The Moon, in turn, revolves around the Earth in its orbit. Eventually, the three celestial bodies will align in a straight line. Thus, this leads to the formation of an eclipse. As a result, neither can be seen in space by the observer. There are two types of eclipses on Earth:
- Solar Eclipse
- Lunar Eclipse
What is Solar Eclipse?
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A Solar Eclipse occurs when the Moon passes between the Sun and the Earth, partially or completely blocking the Sun's rays and casting a shadow on portions of the Earth. This happens when the Sun, Moon, and Earth are in the same line.
Solar eclipse
It only happens on new moon days because the Moon is between the Earth and the Sun, so the side facing us is the dark side. If everything is in place, the Moon will cast a shadow on us, resulting in a solar eclipse.
Types of solar eclipse
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Solar eclipses are classified into four types:
- Total solar eclipse
A total solar eclipse occurs when the Moon completely obscures the Sun from Earth's perspective. When the Moon's dark silhouette completely obscures the Sun's intensely bright light, the much fainter solar corona can be seen. During any given eclipse, totality occurs only on a narrow track on the Earth's surface. This narrow path is referred to as the path of totality. During a total eclipse, totality can only be seen from a specific area, typically 160 km (100 mi) wide and 16,000 km (10,000 mi) long. A partial eclipse of the Sun may be visible in areas outside this track.
- Partial Eclipse
A partial eclipse occurs when the Sun and Moon are not exactly aligned with the Earth, and the Moon only partially obscures the Sun. This phenomenon can usually be seen from a large portion of the Earth that is not directly in the path of an annular or total eclipse. However, because the umbra never intersects the Earth's surface and passes above the polar regions, some eclipses can only be seen as partial eclipses. Because it takes well over 90% coverage to notice any darkening, partial eclipses have almost no effect on the brightness of the Sun.
- The annular eclipse
An annular eclipse occurs when the Moon, even when perfectly centred in front of the Sun, does not completely obscure it. Because of the Moon's elliptical orbit, it gets closer to Earth. During this type of eclipse, the bright ring around the Moon is known as the "ring of fire."
- Eclipse hybrid
An annular/total eclipse (also known as a hybrid eclipse) alternates between total and annular eclipses. A hybrid eclipse occurs when the magnitude of an eclipse changes during the event from less than one to greater than one, causing the eclipse to appear total near the midpoint and annular near the beginning and end because the sides of the Earth are slightly further away from the Moon.
The Phase of the Total Solar Eclipse
The visual phases seen during a total eclipse are referred to as:
- First contact occurs when the Moon's limb (edge) is directly parallel to the Sun's edge.
- The second contact begins with Baily's Beads (caused by light shining through valleys on the Moon's surface) and progresses to the diamond ring effect. The disc is almost entirely covered.
- Totality occurs when the Moon obscures the entire disc of the Sun, leaving only the solar corona visible.
- The third contact occurs when the first bright light appears, and the Moon's shadow moves away from the observer. A diamond ring may be seen once more.
- Fourth contact—when the Moon's trailing edge no longer overlaps with the solar disc and the eclipse ends.
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What is Lunar Eclipse?
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A lunar eclipse occurs when the Moon passes through the Earth's shadow. This can only happen when the Sun, Earth, and Moon are exactly or very closely aligned (in syzygy), with the Earth between the other two, which can only happen on a full moon night when the Moon is close to either lunar node.
Lunar Eclipse
The Moon's proximity to the lunar node determines the length and type of a lunar eclipse. The reddish colour of a completely eclipsed moon from Earth completely blocks direct sunlight from reaching it, with only light reflected from the lunar surface being refracted by Earth's atmosphere. The same phenomenon that causes a sunset or sunrise to appear reddish occurs with this light: Rayleigh scattering of blue light.
A lunar eclipse can be seen from anywhere on Earth's night side, unlike a solar eclipse, which can only be seen from a small portion of the globe. A lunar eclipse can last up to nearly 2 hours because the Moon's shadow is smaller. In contrast, a total solar eclipse can last only a few minutes at any given location.
Types of lunar eclipse
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The shadow cast by the Earth is divided into two distinct parts: the umbra and the penumbra. Earth completely blocks direct solar radiation within the umbra, the central region of the shadow. However, because the Sun's apparent diameter in the lunar sky is roughly one-quarter that of Earth, the planet only partially blocks direct sunlight within the penumbra or the outer portion of the shadow.
- Penumbral lunar eclipse
This happens when the Moon passes through the penumbra of the Earth. The penumbra causes a subtle dimming of the lunar surface, which is only visible to the naked eye when approximately 70% of the Moon's diameter is immersed in the penumbra of Earth. [2] A total penumbral lunar eclipse is a penumbral eclipse in which the Moon is entirely within Earth's penumbra. When a total penumbral eclipse occurs, the portion of the Moon closest to the umbra may appear slightly darker than the rest of the lunar disc.
- Partial lunar eclipse
This occurs when only a portion of the Moon enters the umbra of Earth, whereas a total lunar eclipse occurs when the entire Moon enters the planet's umbra. Because the Moon's average orbital speed is approximately 1.03 km/s (2,300 mph), or slightly more than its diameter per hour, totality may last up to nearly 107 minutes.
- Total lunar eclipse
This happens when the Moon completely enters the Earth's umbra. The brightness of the lunar limb—the curved edge of the Moon still receiving direct sunlight—will cause the rest of the Moon to appear relatively dim just before complete entry. When the Moon enters a total eclipse, its entire surface becomes more or less uniformly bright. Later, as sunlight strikes the Moon's opposite limb, the overall disc becomes obscured.
This is because, as seen from Earth, the brightness of a lunar limb is generally greater than that of the rest of the surface due to reflections from the many surface irregularities within the limb: sunlight striking these irregularities is always reflected in greater quantities than sunlight striking more central parts, which is why the edges of full moons appear brighter than the rest of the lunar surface.
- Central lunar eclipse
During a total lunar eclipse, the Moon will pass through the centre of Earth's shadow, contacting the antisolar point. This kind of lunar eclipse is unusual. The Moon's relative distance from Earth during an eclipse can affect its duration. When the Moon is near apogee, the farthest point from Earth in its orbit, its orbital speed is the slowest. As the Moon's orbital distance changes, the diameter of the Earth's umbra does not change noticeably.
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Difference Between a Solar and Lunar Eclipse
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The difference between Solar and Lunar eclipse listed below:
| Solar eclipse | Lunar eclipse |
|---|---|
| A solar eclipse occurs when the Moon passes between the Earth and the Sun. | The lunar eclipse occurs when the Earth passes between the Sun and the Moon. |
| It happens once every 18 months. | It happens twice a year. |
| It lasts approximately 5-7 minutes. | It lasts one hour. |
| It was seen in a few places. | It was witnessed in numerous locations. |
| It happens during the day. | It takes place at night. |
| The solar eclipse takes place during the new moon phase. | A lunar eclipse occurs when the Moon is at its full moon phase. |
| If you look directly at something, you risk losing your vision because it damages the retina. | Observing a lunar eclipse with bare eyes is safe because it causes no harm to the eyes. |
Previous Year Questions
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- A particle of mass m is thrown upwards from the surface of the earth… [NEET 2011]
- With what velocity should a particle be projected… [NEET 2001]
Things to Remember
- A solar eclipse occurs when the Moon is between the Sun and the Earth.
- A solar eclipse comprises four types: total, partial, annual and hybrid.
- It is very dangerous to look at the solar eclipse with naked eyes.
- A lunar eclipse occurs when the Earth comes in between the Sun and the Moon.
- A lunar eclipse is mainly classified into two types, total and partial, but other types, like the Penumbral and central lunar eclipse, can also be observed.
Sample Questions
Ques: What is a lunar eclipse? [2 marks]
Ans: A lunar eclipse occurs when the Earth passes between the Sun and the Moon. As a result, the Earth blocks sunlight from reaching the Moon's surface and casts a shadow on it. It takes place on a full moon day. Each year, up to three lunar eclipses can occur.
Ques: What are the dangers of viewing a solar eclipse without the proper equipment? [3 marks]
Ans: The Sun is so bright under normal conditions that staring at it directly isn't easy. However, because so much of the Sun is obscured during an eclipse, staring at it becomes easier and more appealing. Looking at the Sun during an eclipse is just as dangerous as looking at it outside of an eclipse, except during the brief period of totality, when the Sun's disc is completely covered (totality occurs only during a total eclipse and only very briefly; it does not occur during a partial or annular eclipse). Observing the Sun's disc through any optical aid (binoculars, a telescope, or even the viewfinder of an optical camera) is extremely dangerous and can result in irreversible eye damage in a fraction of a second.
Ques: What are comets? [1 mark]
Ans: Comets are small ice and rock fragments that form in the solar system's outermost regions. As their orbit approaches the Sun, the ice on them vaporises, leaving behind a spectacular tail.
Ques: What two types of natural eclipses can be seen from Earth? [1 mark]
Ans: Solar eclipses and lunar eclipses are the two types of natural eclipses that can be seen from Earth.
Ques: How to view the annual and partial solar eclipse? [3 marks]
Ans: The most secure method of viewing the Sun's disc is indirect projection. This can be done by projecting an image of the disc onto a white piece of paper or card using a pair of binoculars (one lens covered), a telescope, or another piece of cardboard with a small hole in it, also known as a pinhole camera. The projected image of the Sun can then be safely viewed; this technique is also useful for observing sunspots and eclipses. However, caution must be exercised to ensure that no one looks directly into the projector (telescope, pinhole, etc.). Viewing the Sun's disc on a video display screen is safe, but direct sunlight exposure may damage the camera.
Ques: What is the definition of a satellite? [1 mark]
Ans: A satellite is any object that orbits the Sun, Earth, or any other massive planet. There are primarily two types of satellites: manufactured and natural.
Ques: What happens if we see the solar eclipse with the naked eye? [2 marks]
Ans: Even a few seconds of direct exposure to the Sun's photosphere (the bright disc of the Sun itself) can cause permanent damage to the eye's retina due to the intense visible and invisible radiation emitted by the photosphere. This damage can result in vision impairment, including blindness. Because the retina lacks pain sensitivity and the effects of retinal damage can take hours to manifest, there is no warning that an injury is occurring.
Ques: What are asteroids? [1 mark]
Ans: Small, irregularly shaped metal or mineral rocks that orbit the Sun are asteroids. The asteroid belt, which lies between Mars and Jupiter, contains most of them.
Ques: What is an eclipse? [1 mark]
Ans: An eclipse is a celestial event that occurs when a spacecraft or astronomical body passes into the shadow of another body or object between it and the observer.
Ques: What is a solar eclipse? [2 marks]
Ans: A solar eclipse occurs when the Moon passes between the Sun and the Earth. As a result, the Moon obscures sunlight and casts a shadow on Earth's surface. This happens when the Moon is new. Each year, up to five solar eclipses can occur.
Ques: What are the three kinds of solar eclipses? [1 mark]
Ans: Solar eclipses are classified into three types: partial, annular, and total.
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