Eclipse – Solar and Lunar – UPSC Geography Notes

Eclipses, a frequently observed astronomical event, come in various forms, each captivating the attention of both experts and the general public. The term “eclipse” finds its origin in ancient Greek words denoting ‘abandonment’ or ‘darkening of a heavenly body’.

Throughout history, diverse cultures have woven myths and tales to interpret the momentary obscuring of the Sun or the Moon, often associating eclipses with a sense of foreboding. In recent centuries, astronomers and scientists have intensified their exploration of natural phenomena, including the tracking and analysis of eclipses.

The most recent total lunar eclipse, a spectacle witnessed on November 8, 2022, left enthusiasts eagerly anticipating the next total lunar eclipse, known as the ‘blood moon lunar eclipse’, projected to occur on March 13/14, 2025.

On the other hand, the last partial solar eclipse took place on October 25, and stargazers can anticipate the subsequent partial solar event on August 2, 2027.

Solar Eclipse

What is Eclipse?

An eclipse, an astronomical occurrence, results from the temporary obstruction of one celestial body or spacecraft passing into the shadow of another or being obscured by the passage of another object in front of it.

Syzygy, a term used to describe the alignment of three heavenly bodies, finds its roots in the ancient Greek word ‘syzygia’, signifying a yoking together or conjoining.

Moreover, the notion of an eclipse is also applicable when a spacecraft is positioned to witness two celestial bodies aligned in this manner, either during a transit or an occultation, the latter indicating partial concealment.

On Earth, two kinds of eclipses are observable:

  • Solar eclipses – denoting the occultation of the Sun
  • Lunar eclipses – representing the occultations of the Moon

These phenomena occur when the Sun, Earth, and the Moon align in a straight or nearly straight configuration.

Solar Eclipse

Total Solar Eclipse

During solar eclipses, the alignment of the Sun, the Moon, and Earth, whether partial or total, offers a distinctive and thrilling spectacle of either the Sun or the Moon, depending on their configuration.

This phenomenon occurs when the Moon moves between the Sun and Earth, creating a shadow that partially or completely obscures the Sun’s light in specific regions on Earth.

Given the distinct orbital planes of the Moon, the Sun, and the Earth, such occurrences are relatively rare, as they rely on precise alignment. These alignment periods, known as eclipse seasons, take place twice a year.

In the case of a solar event, the Moon projects two shadows onto Earth:

  • The umbra: Representing the dark core of the Moon’s shadow, the umbra diminishes in size as it nears Earth. Individuals positioned within the umbra experience a total eclipse.
  • The penumbra: The penumbra, on the other hand, enlarges as it approaches Earth. Those situated within the penumbra witness a partial eclipse.

Solar eclipses occur approximately every 18 months in various locations around the globe. Unlike lunar phenomena, solar occultations endure for only a brief span of a few minutes.

Total Solar

During a total solar eclipse, the Moon moves between the Sun and Earth, completely obscuring the Sun’s surface.

Individuals situated within the heart of the Moon’s shadow where it intersects with Earth encounter a complete occultation. The sky darkens, resembling the onset of either dawn or dusk.

Under clear skies, observers within the path of a total solar eclipse have the opportunity to witness the Sun’s corona, its outer atmosphere typically concealed by the Sun’s radiant face.

Notably, during a total solar occultation, viewers briefly have the option to remove their eclipse glasses as the Moon fully obstructs the Sun, a unique feature distinct from other types of solar eclipses.

Annular Solar

An annular solar eclipse occurs when the Moon traverses between the Sun and Earth, particularly at or close to its farthest position from Earth.

Given the Moon’s increased distance from Earth, it appears comparatively smaller than the Sun, failing to entirely obscure it.

Consequently, the Moon presents itself as a dark disc set against a broader, luminous disc, producing the impression of a ring encircling the Moon.

Partial Solar

During a partial solar eclipse, the Moon moves between the Sun and Earth, yet the three celestial bodies are not precisely aligned.

As a consequence, only a segment of the Sun seems to be concealed, resulting in its distinctive crescent shape.

Individuals situated beyond the region enveloped by the Moon’s central shadow witness a partial solar eclipse during total or annular solar occultations.

Hybrid Solar Eclipse

A hybrid solar eclipse occurs when the curved surface of the Earth causes an eclipse to transition between annular and total as the Moon’s shadow traverses the planet’s surface.

Lunar Eclipse

Lunar Eclipse

During a lunar eclipse, the Moon traverses through the Earth’s shadow, losing its inherent luminosity and shining instead by reflecting the Sun’s rays off its surface.

The Earth’s shadow encompasses three distinct regions:

  • Umbra – the central, darker section
  • Penumbra – the outer region
  • Antumbra – the partially shaded area beyond the umbra

This phenomenon exclusively occurs during a full moon, when the Moon is positioned on the opposite side of the Earth from the Sun.

Unlike a solar eclipse, a lunar eclipse is visible from nearly an entire hemisphere, making it more commonly viewable from specific vantage points. A lunar eclipse typically endures for an extended duration, spanning many hours, with the totality phase itself lasting around 30 minutes to over an hour on average.

Total Lunar

During a total lunar eclipse, the Earth’s umbra, the central and darker portion of its shadow, blankets the Moon’s surface.

However, even amidst a total lunar eclipse, some light reflections persist on the Moon, preventing complete darkness. Sunlight, refracted by the Earth’s atmosphere, penetrates the umbra, casting a subdued light.

As sunlight travels through the atmosphere, it is refracted towards the Earth’s surface, with shorter wavelength colors being scattered and filtered out, allowing longer wavelengths, such as orange and red, to continue their path through the atmosphere. This refracted light is once again directed toward the surface of the fully eclipsed Moon, lending it a reddish-orange radiance. This distinctive appearance has led to the historical depiction of such lunar phenomena as “Blood Moons.”

Partial Lunar

During a partial lunar eclipse, a fraction of the Moon’s surface is concealed as Earth’s umbra obstructs only a portion of it. This phenomenon occurs when the central and darkest section of Earth’s shadow, known as the umbra, covers a small segment of the Moon’s surface, while the remaining portion is enveloped by the penumbra, the outer part of Earth’s shadow.

Penumbral Lunar

  • During a penumbral lunar eclipse, the Moon traverses through the subtle penumbral section of Earth’s shadow. In this scenario, the Earth impedes some of the direct sunlight from reaching the Moon’s surface, shrouding either all or a portion of the Moon with the outer part of its shadow, referred to as the penumbra.
  • Because the penumbra is notably fainter than the Earth’s shadow’s darker core, the umbra, distinguishing a penumbral eclipse of the Moon from a regular full moon can often prove challenging.

Planet Transits

A transit occurs when a planet moves between Earth and the Sun. From our vantage point, only Mercury and Venus are observable as they transit across the face of the Sun. This is due to their orbits lying within that of the Earth, making them the only two planets in the solar system capable of such a celestial display.

Historical records

Ancient civilizations have preserved historical accounts of solar and lunar eclipses, enabling the chronological dating of historical records using eclipse dates.

Noteworthy recordings of these celestial phenomena date back to a Syrian clay tablet in 1223 BCE, an Irish observation in 3340 BCE, Babylonian records from the 13th century BCE, as well as accounts from ancient Greek and Chinese civilizations.

In the 5th century CE, the Indian mathematician and astronomer Aryabhata provided a scientific explanation of solar and lunar eclipses in his treatise Aryabhatiya. Aryabhata’s work elucidated that the Moon and planets reflect sunlight and elucidated the occurrences of eclipses in terms of shadows cast by and falling on Earth. His computations accurately determined the size of the eclipsed portion during an eclipse.

FAQs on Eclipse

Q. Is There an Eclipse Today?

A. Eclipse occurrences are not daily events. To know about any upcoming eclipses, it’s recommended to check reliable astronomical sources or use dedicated eclipse tracking applications.

Q. What Causes an Eclipse of the Moon?

A. A lunar eclipse occurs when the Earth is positioned directly between the Sun and the Moon, resulting in the Earth’s shadow being cast over the Moon.

Q. What is the Meaning of an Eclipse?

A. An eclipse is an astronomical event that occurs when one celestial body moves into the shadow of another celestial body, leading to a temporary obscuring of light.

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