From UPSC perspective, the following things are important :
Prelims level : Solar Eclipse and related terms, Summer Solstice
Mains level : Not Much
A rare celestial event, an annular solar eclipse popularly called as the ‘ring of fire’ eclipse, will be visible on June 21, 2020 from some parts of Northern India. The first solar eclipse of this year takes place on the summer solstice, which is the longest day in the Northern Hemisphere.
Try this question from CSP 2019:
Q. On 21st June, the Sun
(a) Does not set below the horizon at the Arctic Circle
(b) Does not set below the horizon at Antarctic Circle
(c) Shines vertically overhead at noon on the Equator
(d) Shines vertically overhead at the Tropic of Capricorn
What is the Solar Eclipse?
- A Solar Eclipse happens when the moon while orbiting the Earth comes in between the sun and the Earth, due to which the moon blocks the sun’s light from reaching the Earth, causing an eclipse of the sun or a solar eclipse.
- According to NASA, people who are able to view the total solar eclipse are in the centre of the moon’s shadow as and when it hits the Earth.
- There are three types of eclipses: one is a total solar eclipse, which is visible only from a small area on Earth. A total solar eclipse happens when the sun, moon and Earth are in a direct line.
- The second type of a solar eclipse is a partial solar, in which the shadow of the moon appears on a small part of the sun.
Annular Solar Eclipse
- The third kind is an annular solar eclipse, which happens when the moon is farthest from the Earth, which is why it seems smaller.
- In this type of an eclipse, the moon does not block the sun completely, but looks like a “dark disk on top of a larger sun-coloured disk” forming a “ring of fire”.
- Furthermore, during a solar eclipse, the moon casts two shadows on the Earth; the first one is called the umbra, which gets smaller as it reaches the Earth.
- The second one is called the penumbra, which gets larger as it reaches the Earth.
- According to NASA, people standing in the umbra see a total eclipse and those standing in the penumbra see a partial eclipse.
Why the study of solar eclipse is crucial?
- One of the reasons that NASA studies solar eclipses is to study the top layer of the sun called the corona.
- During an annular eclipse, NASA uses ground and space instruments to view this top layer when the sun’s glare is blocked by the moon.
Back2Basics: Summer Solstice
- The summer solstice occurs when one of the Earth’s poles has its maximum tilt toward the Sun.
- It happens twice yearly, once in each hemisphere (Northern and Southern).
- For that hemisphere, the summer solstice is when the Sun reaches its highest position in the sky and is the day with the longest period of daylight.
- Within the Arctic circle (for the northern hemisphere) or Antarctic circle (for the southern hemisphere), there is continuous daylight around the summer solstice.
- On the summer solstice, Earth’s maximum axial tilt toward the Sun is 23.44°. Likewise, the Sun’s declination from the celestial equator is 23.44°.