NCERT Solutions Curiosity Chapter 12 & 24012.3 Our Solar System — In-text Questions
Book page 238, 239 Updated on2026-09-05
Q1.
Which star is closest to us?
Answer
The Sun. The Sun is a star — the star nearest to the Earth.
Distance of the Sun from the Earth ≈ 150 million km = 1 astronomical unit (au) Next nearest star: Proxima Centauri, about 269000 au away That is about 269000 times farther than the Sun.
Why this matters: because it is so close, the Sun looks like a huge disc and floods the Earth with heat and light. Proxima Centauri is the same kind of object, but at 269000 times the distance it is not even visible to the naked eye.
Did you know? The astronomical unit (au) was invented precisely because kilometres are clumsy for space. Saying "Jupiter is about 5 au from the Sun" is much easier than writing 778 million km.
Q2.
Our Sun is also a star. So how is it that the Sun appears big and lights up the sky while the other stars look like bright dots in the night sky and are not even visible during the day time?
Answer
The difference is distance, not size.
The Sun is very much closer to us than any other star, so it appears as a large, blazing disc. It is about 100 times bigger than the Earth in diameter, and even so it looks small compared with how big it really is, because it is 150 million km away.
All other stars are enormously farther — the nearest is 269000 times as far. At that distance even a giant star shrinks to a point of light. Many of those points are actually bigger than our Sun.
During the daytime the Sun's light is so overwhelmingly bright — and the air scatters it all over the sky — that the feeble light of the other stars is completely drowned out. The stars have not gone anywhere; we simply cannot pick them out against a bright sky.
An everyday parallel: a candle flame is easily seen in a dark room, but hold the same candle next to a stadium floodlight and it disappears. The candle is still burning — it is just outshone. The stars are the candles and the daytime sky is the floodlight.
Did you know? An astronaut standing on the Moon, which has almost no atmosphere to scatter sunlight, can see the stars even while the Sun is up. It is our air, lit by the Sun, that hides them from us.
Q3.
Are stars the only objects in the sky? Or, are there more objects which we may not have noticed?
Answer
There are many more objects. Stars are only the most obvious ones. Our Earth, along with several other kinds of object and the Sun, together form our Solar System.
Object
What it is
Example
The Sun
A star — the largest and heaviest object of the Solar System
Source of almost all the energy in the Solar System
Planets
Large, nearly spherical bodies that revolve around the Sun
Mercury … Neptune (eight in all)
Satellites (moons)
Bodies that move around planets
Earth's Moon; Mars has two moons
Asteroids
Small, rocky, irregular bodies, mostly between Mars and Jupiter
The asteroid belt
Comets
Dust, gas, rock and ice; grow a long tail near the Sun
Halley's Comet (Dhūmaketu)
Dwarf planets
Bodies that revolve round the Sun but do not meet the full definition of a planet
Pluto
The movement of an object around the Sun is called revolution. The spinning of a body about its own axis is called rotation. Earth: one revolution ≈ 1 year | one rotation ≈ 24 hours = one day
Tip: do not mix the two words. Revolution = going round something else (Earth round the Sun). Rotation = spinning on the spot (Earth on its own axis). A merry-go-round rotates; you revolve around its centre.