Context:
An annular solar eclipse was visible in parts of South America on October 2 while a partial solar eclipse was visible in parts of South America, Antarctica, North America, the Atlantic Ocean, and the Pacific Ocean.
Relevance:
GS-I Geography
Dimensions of the Article:
- Solar eclipse
- Types of Solar Eclipse
- Significant observations during solar eclipses
Solar eclipse
- A solar eclipse occurs when a portion of the Earth is covered in a shadow cast by the Moon which fully or partially blocks sunlight.
- This occurs when the Sun, Moon and Earth are aligned.
- Such alignment coincides with a new moon (syzygy) indicating the Moon is closest to the ecliptic plane.
- The Sun’s distance from Earth is about 400 times the Moon’s distance, and the Sun’s diameter is about 400 times the Moon’s diameter. Because these ratios are approximately the same, the Sun and the Moon as seen from Earth appear to be approximately the same size: about 0.5 degree of arc in angular measure.
Types of Solar Eclipse
Total Solar Eclipse:
- During a total solar eclipse, the Moon completely covers the Sun from view as seen from a specific location on Earth.
- The sky darkens significantly, and the Sun’s outer atmosphere, known as the solar corona, becomes visible as a bright halo around the obscured Sun.
- Total solar eclipses are rare and can only be observed from a limited geographic area along the eclipse’s path of totality.
Partial Solar Eclipse:
- In a partial solar eclipse, the Moon partially covers the Sun, obscuring only a portion of the Sun’s disk.
- This type of eclipse is visible over a broader geographic region than a total eclipse since it occurs when the Moon partially passes in front of the Sun.
Annular Solar Eclipse:
- An annular solar eclipse occurs when the Moon is near its apogee (farthest from Earth) in its elliptical orbit, causing it to appear smaller than the Sun.
- As a result, the Moon does not completely cover the Sun, and a ring of the Sun’s outer edge, known as the “ring of fire” or annulus, remains visible around the Moon.
- Annular eclipses create a unique and visually striking spectacle.
Hybrid Solar Eclipse (Annular-Total Eclipse):
- A hybrid eclipse is a rare event where an eclipse appears as a total eclipse from some locations on Earth’s surface and as an annular eclipse from others.
- The type of eclipse experienced depends on the viewer’s location within the eclipse’s path.
Why does the Solar Eclipse not occur during every new moon?
- If the Moon were in a perfectly circular orbit, a little closer to the Earth, and in the same orbital plane, there would be total solar eclipses every new moon.
- However, since the Moon’s orbit is tilted at more than 5 degrees to the Earth’s orbit around the Sun, its shadow usually misses Earth.
What are the factors that affect the duration of the eclipse?
- The Moon being almost exactly at perigee (making its angular diameter as large as possible).
- The Earth being very near aphelion (furthest away from the Sun in its elliptical orbit, making its angular diameter nearly as small as possible).
- The midpoint of the eclipse being very close to the Earth’s equator, where the rotational velocity is greatest.
- The vector of the eclipse path at the midpoint of the eclipse aligning with the vector of the Earth’s rotation (i.e. not diagonal but due east).
- The midpoint of the eclipse being near the subsolar point (the part of the Earth closest to the Sun).
Significant observations during solar eclipses
- A total solar eclipse provides a rare opportunity to observe the corona (the outer layer of the Sun’s atmosphere). Normally this is not visible because the photosphere is much brighter than the corona.
- Eclipses may cause the temperature to decrease by up to 3 °C.
- There is a long history of observations of gravity-related phenomena during solar eclipses, especially during the period of totality.
- Confirmation of Einstein’s theory: The observation of a total solar eclipse of 1919, helped to confirm Einstein’s theory of general relativity. By comparing the apparent distance between stars in the constellation Taurus, with and without the Sun between them, Arthur Eddington stated that the theoretical predictions about gravitational lenses were confirmed.
Precautions to take while viewing Solar eclipse
- Looking directly at the photosphere of the Sun (the bright disk of the Sun itself), even for just a few seconds, can cause permanent damage to the retina of the eye, because of the intense visible and invisible radiation that the photosphere emits.
- This damage can result in impairment of vision, up to and including blindness.
- The retina has no sensitivity to pain, and the effects of retinal damage may not appear for hours, so there is no warning that injury is occurring.
- Under normal conditions, the Sun is so bright that it is difficult to stare at it directly, however, during an eclipse, with so much of the Sun covered, it is easier and more tempting to stare at it.
- Special eye protection or indirect viewing techniques are used when viewing a solar eclipse.
- It is safe to view only the total phase of a total solar eclipse with the unaided eye and without protection.
-Source: The Hindu
