The Earth In Solar System - Free MCQ Practice Test with solutions, UPSC

Stars are celestial objects that can produce their own light. They are extremely hot and extremely large. They are made up of gases (mostly hydrogen and helium). The Sun is a star.

The Inner or Terrestrial Planets

• Four planets, namely Mercury, Venus, the Earth, and Mars constitute the terrestrial group.

• Jupiter is a non-terrestrial planet.

The Earth is the third nearest planet to the Sun. In size, it is the fifth-largest planet.

It is slightly flattened at the poles. That is why its shape is described as a Geoid( It means an earth-like shape).

From outer space, the Earth appears blue because its two-thirds of the surface is covered by water. (Therefore, called a blue planet) 

Asteroids are numerous tiny bodies that also move around the Sun apart from the stars, planets, and satellites. They are found between the orbits of Mars and Jupiter.

The moon moves around the earth in 27 days. It takes the exact same time to complete one spin. As a result, only one side of the moon is visible to us on the earth. This characteristic of the moon is responsible for the phenomena of the full moon(Poornima) and New moon night(Amavasya).

The IAU resolves the planet's definition issue. It recognized a planet if it has the following characteristics. A planet is a celestial body that :
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
(c) not a satellite (moon) of another object, and
(d) has cleared the neighbourhood around its orbit.

Pluto’s classification as a planet has had a history of changes. Since 2006, per the International Astronomical Union’s planetary criteria, Pluto isn’t considered a planet because it hasn’t cleared the neighborhood around its orbit of other objects. However, it does meet IAU’s criteria for what constitutes a dwarf planet.

►Statement 1 is incorrect -A meteoroid is a small space rock moving through a solar system. Space is full of meteoroids. When they enter the earth's atmosphere, they become visible as meteors.

►Statement 2 is incorrect - Venus Planet shines so brightly that it is the first “ planet-like star” to appear in the sky after the Sun sets or the last to disappear before the Sun rises. That’s why Venus planet is called morning star or evening star.

►Pair 1 is correct - The Earth is the third nearest planet to the Sun. In size, it is the fifth-largest planet.

►Pair 2 is correct- The moon is a bit more than one-fourth (27 percent) the size of Earth, a much smaller ratio (1:4) than any other planets and their moons.

►Pair 3 is incorrect- Venus is considered as ‘Earth-Twin’ because its size and shape are very much similar to that of the Earth.