Universe & Solar System – NDA Geography PYQs

Question 1 [NDA 2008-II]
Which one of the following statements is/are correct with regard to the Milky Way?

1. It is a spiral galaxy.
2. The Solar System resides in one of its spiral arms.

Select the correct answer:
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

Answer: (c) Both 1 and 2
The Milky Way is a spiral galaxy with a bright centre and curved arms extending outward. Our Solar System is located in one of the outer spiral arms — not at the centre. Both statements are correct.

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Question 2 [NDA 2009-I]
In which one of the following is a great dark plain called Maria found?
(a) Earth
(b) Mars
(c) Jupiter
(d) Moon

Answer: (d) Moon
Maria are large dark plains on the Moon’s surface formed by ancient volcanic eruptions billions of years ago. Early astronomers mistook them for seas. The name Maria comes from the Latin word for sea.

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Question 3 [NDA 2017-II]
Light year is a measure of?
(a) Time
(b) Distance
(c) Total amount of light falling on the Earth in a year
(d) Average luminosity

Answer: (b) Distance
A light year is the distance that light travels in one year — approximately 9.46 trillion kilometres. Despite the word “year” appearing in it, a light year measures distance, not time. It is used to express distances between stars and galaxies.

Question 4 [NDA 2018-I]
Light year is a unit for measurement of:
(a) Age of universe
(b) Very small time intervals
(c) Very high temperature
(d) Very large distance

Answer: (d) Very large distance
A light year is used to measure very large distances in space — the distances between stars and between galaxies. It is the distance light travels in one year. It has nothing to do with time, temperature, or the age of the Universe.

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Question 5 [NDA 2019-I]
Light year is a unit of measurement of:
(a) Very large distances
(b) Time interval in years
(c) Amount of light received on Earth in a year
(d) Mass of atoms

Answer: (a) Very large distances
This same fact has appeared in NDA 2017-II, 2018-I, and 2019-I. A light year measures distance — the distance light travels in one year. It is used in astronomy because the distances between stars are so enormous that kilometres would require impossibly large numbers.

Question 6 [NDA 2019-I]
Black hole is a:
(a) Huge black star which has zero acceleration due to gravity on its surface
(b) Star which has moderate acceleration due to gravity on its surface
(c) Star which has collapsed into itself and has large acceleration due to gravity on its surface
(d) Star which has collapsed into itself and has zero acceleration due to gravity on its surface

Answer: (c) Star which has collapsed into itself and has large acceleration due to gravity on its surface
A black hole forms when a massive star collapses under its own gravity at the end of its life. The gravity becomes so extreme that even light cannot escape. A black hole does not have zero gravity — it has the most extreme gravity of any known object.

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Question 7 [NDA 2021-I]
Which one of the following planets has the highest density?
(a) Mercury
(b) Venus
(c) Jupiter
(d) Earth

Answer: (d) Earth
Earth is the densest planet in the Solar System with a density of about 5.51 g/cm³. This is because Earth has a large iron-nickel core which is extremely dense. Jupiter is the largest planet but it is made mostly of light gases, giving it a much lower density.

Question 8 [NDA 2021-II]
Which one from among the following planets is largest in size?
(a) Earth
(b) Venus
(c) Mars
(d) Mercury

Answer: (b) Venus
Among these four options, Venus is the largest. Venus is slightly smaller than Earth in reality, but Earth is not one of the options here. Among Earth, Venus, Mars, and Mercury — Venus has the largest diameter, followed by Mars, then Mercury.

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Question 9 [NDA 2023-I]
Which one of the following astronomers proved that the Earth and other planets revolve around the Sun?
(a) Copernicus
(b) Kepler
(c) Galileo
(d) Newton

Answer: (a) Copernicus
Nicolaus Copernicus proposed the heliocentric model of the Solar System in 1543 — placing the Sun at the centre rather than the Earth. Before Copernicus, the geocentric (Earth-centred) model proposed by Ptolemy was widely accepted. Kepler later showed that orbits are elliptical. Galileo provided telescopic evidence supporting Copernicus.