The Solar System

11. Which one of the following statements is not correct?

Which one of the following statements is not correct?

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Position of the Sun, Earth and Moon in a straight line of 180° angle is known as syzygy.
Syzygy conjunction causes solar eclipse.
Syzygy opposition causes lunar eclipse.
Syzygy conjunction occurs at the time of perihelion only.
This question was previously asked in
UPSC CDS-2 – 2016
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Statement D is not correct.
– Syzygy is the alignment of three celestial bodies. A 180° alignment describes a syzygy.
– A syzygy conjunction (Moon between Sun and Earth) causes a solar eclipse.
– A syzygy opposition (Earth between Sun and Moon) causes a lunar eclipse.
– Syzygy conjunction (New Moon) occurs approximately once a lunar cycle (around 29.5 days). Perihelion (Earth closest to the Sun) occurs only once a year (around January 3rd). Therefore, syzygy conjunction does not occur only at the time of perihelion.
Perihelion is an orbital term describing the Earth’s position relative to the Sun in its elliptical orbit. Syzygy is a geometric term describing the alignment of three celestial bodies, typically the Sun, Earth, and Moon, which is related to the phases of the Moon and the occurrence of eclipses.

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12. Which of the following groups of planets is termed as ‘gas planets’ as

Which of the following groups of planets is termed as ‘gas planets’ as they are composed primarily of lighter ices, liquids and gases?

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Mars, Jupiter, Neptune, Uranus
Jupiter, Uranus, Neptune, Saturn
Saturn, Mars, Jupiter, Neptune
Neptune, Saturn, Mars, Uranus
This question was previously asked in
UPSC CDS-1 – 2023
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The solar system’s planets are broadly classified into terrestrial planets and Jovian planets (or gas giants). The Jovian planets are located further from the Sun and are significantly larger and less dense than terrestrial planets. They are composed primarily of lighter elements like hydrogen and helium, as well as ices and liquids. This group includes Jupiter, Saturn, Uranus, and Neptune.
The inner planets (Mercury, Venus, Earth, Mars) are terrestrial, meaning they are rocky and have solid surfaces. The outer planets (Jupiter, Saturn, Uranus, Neptune) are Jovian or gas giants.
Jupiter and Saturn are often referred to as gas giants, composed mainly of hydrogen and helium. Uranus and Neptune are sometimes called ice giants, as they have a higher proportion of volatile substances (like water, ammonia, and methane) in their interior compared to Jupiter and Saturn, although they also contain significant amounts of hydrogen and helium. The term ‘gas planets’ or ‘gas giants’ commonly refers to all four Jovian planets.

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13. Which of the following planets of our solar system has least mass?

Which of the following planets of our solar system has least mass?

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Neptune
Jupiter
Mars
Mercury
This question was previously asked in
UPSC CDS-1 – 2019
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The correct option is D.
Comparing the masses of the given planets:
– Neptune: approx. 1.02 x 10^26 kg
– Jupiter: approx. 1.90 x 10^27 kg (most massive in the solar system)
– Mars: approx. 6.42 x 10^23 kg
– Mercury: approx. 3.30 x 10^23 kg
Comparing these values, Mercury has the smallest mass. In fact, Mercury is the smallest planet in the solar system both in terms of mass and radius.
The order of planets by mass (from least to most massive) is: Mercury, Mars, Venus, Earth, Uranus, Neptune, Saturn, Jupiter.

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14. Which one of the following is the correct sequence of the given planet

Which one of the following is the correct sequence of the given planets in increasing order of their size (diameter) ?

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Mars - Venus - Earth - Mercury - Uranus
Mercury - Mars - Venus - Earth - Uranus
Mercury - Mars - Venus - Earth
Venus - Mercury - Mars - Earth - Uranus
This question was previously asked in
UPSC CDS-1 – 2016
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To arrange the given planets in increasing order of their size (diameter), we need to know their relative sizes. The approximate diameters relative to Earth’s diameter are: Mercury (~0.38), Mars (~0.53), Venus (~0.95), Earth (1.00), Uranus (~4.0). Arranging these values in increasing order gives the sequence: Mercury < Mars < Venus < Earth < Uranus.
The sequence of planets from the Sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Their sizes vary, with the inner terrestrial planets being smaller than the outer gas/ice giants.
The largest planets in our solar system are Jupiter and Saturn, followed by Uranus and Neptune. The smallest planets are Mercury, Mars, Venus, and Earth, in increasing order of size.

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