Complete, step-by-step solutions for every in-text question and every “Let us enhance our learning” exercise — with the original textbook figures, star patterns connected, riddles solved, and clear explanations.
Look at Fig. 12.2, imagine a pattern among the stars, connect them with lines, and name an object or animal it resembles. Compare with friends — are everyone’s patterns the same?
Fig. 12.2: A part of the night sky (as given in the textbook)
Solution
This activity is open-ended — there is no single “correct” pattern. Any set of lines you draw connecting the bright dots to form a recognisable shape (an animal, a kite, a cup, a face) is a valid answer, exactly as ancient sky-watchers imagined animals and objects among the stars. When you compare your pattern with a friend’s, you will almost certainly find that everyone’s patterns, names, and stories are different — because the same set of stars can be joined in many different ways depending on imagination. This is exactly how different cultures around the world ended up with different names and stories for the same constellations.
Do we find patterns among the stars just for fun, or is there some use of these patterns?
Solution
It is not just for fun. Recognising star patterns — constellations — was a genuinely useful skill in ancient times. Long before the invention of the magnetic compass or modern technology, sailors and travellers used familiar star patterns to find directions at sea and on land. Even today, this method is kept as a backup for navigation in emergencies. Beyond navigation, constellations also help astronomers quickly locate and identify regions of the sky for study.
Discussion
Identify the constellations and stars shown in Fig. 12.3, and describe how they are imagined together.
Fig. 12.3: Some constellations and stars (as given in the textbook)
Solution
Orion — often imagined as a hunter; the three close stars in the middle represent his belt.
Canis Major — imagined as Orion’s hunting dog, following him. It contains Sirius, the brightest star in the entire night sky.
Taurus — imagined as a bull that the hunter Orion, with his dog, is battling.
In Indian astronomy, some of these same stars have their own names: Betelgeuse (in Orion) is called Ārdrā, and the star cluster Pleiades (in Taurus) is called Kṛittikā, while Aldebaran (in Taurus) is called Rohiṇī.
The same constellations with their Indian nakṣhatra names (as given in the textbook)
Discussion
What are the Big Dipper, Little Dipper, and the Pole Star? How does the Pole Star help us?
Fig. 12.4: Big Dipper, Little Dipper and Pole Star (as given in the textbook)
Solution
The Big Dipper and the Little Dipper are two easily recognisable star patterns — the Big Dipper lies within the constellation Ursa Major (called Saptaṛiṣhi in India) and the Little Dipper lies within Ursa Minor. The Pole Star (Polaris) is part of the Little Dipper, and it is special because it appears nearly stationary in the North direction throughout the night — this makes it extremely useful for locating North in the Northern Hemisphere.
Can we try to find any constellation or star of our choice on any night from our location?
Solution
Not always. Not all stars and constellations are visible from every place on Earth or on every night of the year — for example, the Pole Star cannot be seen at all from the Southern Hemisphere. To successfully find a particular star or constellation, you need to know what its pattern looks like and exactly where and when to look for it in the sky. This is why sky mapping apps such as Sky Map or Stellarium, or printed star charts, are so useful — they tell you the correct date, time, and direction to look.
Activity 12.2 · Let us try to locate
How do you locate the Big Dipper, and then use it to find the Pole Star?
Solution — Method
Around 9 p.m. in summer, face the northern part of the sky and look for the Big Dipper’s distinctive “ladle” shape.
Find the two stars at the end of the Big Dipper’s cup (the outer edge, farthest from the handle).
Imagine a straight line joining these two stars and extending further towards the north.
Travel along this line for about five times the distance between those two stars — this line leads you to a star that is not very bright. That star is the Pole Star.
Activity 12.3 · Let us try to identify
How do you locate Orion, and then use it to find the star Sirius?
Solution — Method
In India, Orion is best viewed from December to April, after sunset.
Look for three bright stars in a short straight line near the middle of the sky region — these form the “belt” of the hunter Orion, and are the easiest way to spot the constellation.
Once Orion is identified, imagine a straight line passing through these three belt stars and extend it towards the east.
This imaginary line leads directly to Sirius — the brightest star in the night sky.
Discussion
Which star is closest to us?
Solution
The Sun is the star closest to us — it is about 150 million km (1 astronomical unit, au) away, which is why it appears so much bigger and brighter than every other star in the sky.
Our Sun is also a star. So how is it that the Sun appears big and lights up the sky while other stars look like bright dots and aren’t even visible in the daytime?
Fig. 12.7: An artist’s representation of the Solar System (as given in the textbook, not to scale)
Solution
The Sun looks huge and bright simply because it is far closer to us than any other star — only about 150 million km (1 au) away, compared to the next-nearest star, Proxima Centauri, which is roughly 269,000 times farther. Even though many other stars are actually much bigger than the Sun, their enormous distance makes them appear as tiny points of light. During the daytime, the Sun’s intense brightness scatters sunlight throughout Earth’s atmosphere, making the entire sky glow — this overwhelms the much fainter light of distant stars, so we cannot see them until it gets dark again.
Discussion
Are stars the only objects in the sky, or are there more objects that we may not have noticed?
Solution
Stars are not the only objects. Along with the Sun (a star), there are planets, their moons (satellites), asteroids, and comets — all moving mostly around the Sun. Together with the Sun, these objects make up our Solar System. Most of these bodies do not produce their own light; we see them only because they reflect sunlight.
Discussion
Can we identify a planet also, the way we identified the constellations?
Solution
Yes. Venus is the easiest to spot — after the Sun and the Moon, it is the brightest object in the sky. Mercury, Mars, Jupiter, and Saturn can also be seen with the naked eye, though they look like shining dots similar to stars. The key way to tell a planet apart from a star is that stars twinkle a lot, while planets do not twinkle (or twinkle very little).
Activity 12.4 · Let us try to identify
How can Venus be located in the sky?
Solution — Method
Using a sky app to choose the right date, Venus can be spotted at either dawn or dusk:
At dawn: look near the Eastern direction, before sunrise.
At dusk: look near the Western direction, after sunset.
This is why Venus is popularly called the “Morning Star” or “Evening Star,” even though it is actually a planet, not a star.
Discussion
How can we see the planets which are not visible to the naked eye?
Solution
We can use a pair of binoculars or an instrument called a telescope. These tools gather much more light than our eyes can on their own and magnify distant objects, making faint and dim objects — invisible to the naked eye — appear brighter, larger, and clearer.
Discussion
We know that planets move around the Sun. Are there any objects that move around planets?
Solution
Yes — objects that move around planets are called satellites. Natural satellites are commonly known as moons. For example, Earth has one Moon, Mars has two moons, while Jupiter, Saturn, Uranus, and Neptune each have a large number of moons.
Fig. 12.9: The Moon — (a) image by Cartosat, ISRO (b) close-up by Chandrayaan-3, ISRO (as given in the textbook)
Discussion
What is beyond the Solar System?
Solution
Beyond our Solar System lies a vast collection of stars, gas, and dust called our home galaxy — the Milky Way Galaxy. A galaxy can contain millions to billions of stars, and our entire Solar System is just a tiny part of it. Beyond the Milky Way lie countless other galaxies, together forming what we call the Universe.
12.4 The Milky Way Galaxy
Fig. 12.11: Milky Way Galaxy as seen from a very dark location in Ladakh, India (as given in the textbook)
Solution
There are many more galaxies in the outer space beyond our Milky Way Galaxy. Scientists study these distant galaxies to better understand stars, galaxies, and the Universe as a whole.
Discussion
Is there life anywhere else in the Universe?
Solution
We do not know yet. Scientists have been searching mainly among exoplanets — planets found revolving around stars other than our Sun — for any signs of life. So far, no evidence of life has been found anywhere beyond Earth, but this search is actively continuing.
(i) Solve the riddle. (ii) Make two similar riddles yourself.
Solution (i)
Clue
Reasoning
Letter
In MAN but not in CAN
MAN = M,A,N; CAN = C,A,N → letter unique to MAN
M
In ACE and also in FAN
ACE = A,C,E; FAN = F,A,N → common letter
A
In RAT but not in CAT
RAT = R,A,T; CAT = C,A,T → letter unique to RAT
R
In SUN but not in FUN
SUN = S,U,N; FUN = F,U,N → letter unique to SUN
S
Putting the letters together: M + A + R + S = MARS. The answer is the planet Mars.
Solution (ii) — Two sample riddles
Riddle for VENUS:
My first letter is in VAN but not in FAN
My second letter is in EGG and also in TEN
My third letter is in NET and also in SUN
My fourth letter is in USE but not in USA
My fifth letter is in SUN but not in FUN
I am the planet often seen shining at dawn and dusk. (Answer: V-E-N-U-S)
Riddle for EARTH:
My first letter is in EAT but not in ATE
My second letter is in ANT and also in CAR
My third letter is in RUN and also in TAR
My fourth letter is in TIN but not in PIN
My fifth letter is in HAT and also in THE
I am the only planet known to have life. (Answer: E-A-R-T-H)
3Question
Which of the following is not a member of our Solar System? (i) Sirius (ii) Comets (iii) Asteroids (iv) Pluto
Solution(i) Sirius is not a member of our Solar System. Sirius is a distant star (part of the constellation Canis Major) that shines with its own light and does not revolve around our Sun, unlike comets, asteroids, and Pluto (a dwarf planet), which are all genuine members of the Solar System.
4Question
Which of the following is not a planet of the Sun? (i) Jupiter (ii) Pluto (iii) Neptune (iv) Saturn
Solution(ii) Pluto is not a planet. Although Pluto was originally called a planet when discovered, the International Astronomical Union (IAU) redefined the criteria for what counts as a planet in 2006. Under the new definition, Pluto and other similar small bodies are now classified as dwarf planets.
5Question
Which is the brighter star, the Pole Star or Sirius?
SolutionSirius is the brighter of the two — in fact, it is the brightest star in the entire night sky. The Pole Star, in contrast, is not very bright, which is exactly why finding it requires the careful method of tracing a line from the Big Dipper (as described in Activity 12.2), rather than simply spotting it by its brightness.
6Question
An artist’s representation of the Solar System is given in Fig. 12.12. Is the order of the planets correct? If not, write the correct order in the boxes in the figure.
Fig. 12.12 as given in the textbook (order of planets to be checked)
Solution
No, the order shown in Fig. 12.12 is not correct — comparing the planet colours and features against Fig. 12.7, the 2nd & 3rd planets (Earth and Venus) are swapped, and the 6th & 7th planets (Saturn and Uranus) are swapped. The correct order of the eight planets by increasing distance from the Sun is:
Correct order filled in — Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
7Question
A portion of the night sky with stars is shown in Fig. 12.13. Identify and connect the Big Dipper and Little Dipper patterns, and label the Pole Star.
Fig. 12.13 as given in the textbook
Solution
Comparing the brighter, larger dots in the star field to the shape in Fig. 12.4, the two familiar patterns can be traced as shown below: the Big Dipper (a 6-star zigzag “ladle” shape) on the left, and the Little Dipper (a smaller hook-shaped chain) on the right, ending in the dim Pole Star at its tip — exactly matching the description that the Pole Star “is not very bright.”
Big Dipper and Little Dipper connected, with the Pole Star labelled at the end of the Little Dipper’s handle
8Question
A portion of the night sky is shown in Fig. 12.14. Draw lines to connect the stars for Orion and label the star Sirius.
Fig. 12.14 as given in the textbook
Solution
Using the same method as Fig. 12.3, the brightest, largest stars in this field can be joined to trace Orion’s familiar hourglass shape: two “shoulder” stars at the top, the three close-set “belt” stars in the middle, and two “foot” stars at the bottom. The bright, isolated star seen off to the side (separate from Orion’s pattern) is Sirius — matching how, in the real sky, extending a line through Orion’s belt stars towards the east leads you straight to it.
Orion’s hourglass shape connected (shoulders–belt–feet), with Sirius circled and labelled
9Question
From Earth, you can see stars fading away at dawn and appearing at dusk. During the day we do not see the stars. Explain why.
Solution
Stars are actually present in the sky both day and night — but during the day, sunlight gets scattered by the gases and dust in Earth’s atmosphere, making the entire daytime sky glow brightly. This bright background light is so much stronger than the very faint light reaching us from distant stars that it completely washes them out, making them invisible. As the Sun sets at dusk, the scattered sunlight fades and the sky gradually darkens, so stars become visible one by one, brightest first. The same thing happens in reverse at dawn — as the rising Sun brightens the sky again, the fainter stars disappear first, and the sky eventually becomes too bright for any star to be seen.
10Question
During a clear night, observe the Big Dipper 3–4 times at intervals of 2–3 hours, also locating the Pole Star each time. Does the Big Dipper appear to move? Illustrate with a rough sketch mentioning the time in each case.
Solution
Yes — the Big Dipper appears to slowly move (rotate) across the sky as the night progresses, while the Pole Star stays almost perfectly still. This happens because the Earth keeps rotating on its own axis through the night; since the Pole Star lies almost exactly along the direction of Earth’s rotational axis, it appears fixed, while every other star (including the Big Dipper) appears to trace a large circle around it.
Sketch: the Big Dipper’s position rotates around the fixed Pole Star at 9:00 PM, 11:30 PM, and 2:00 AM on the same night
11Question
Think about the night sky and write a poem or a story on it.
Sample Answer — A short poem
The sky turns dark, the sun says goodnight,
And one by one, the stars take flight.
A hunter with his belt of three,
Strides across for all to see.
A silent dipper made of light,
Points the way through the deep, dark night.
A tiny star that will not stray,
Stands still and shows the traveller’s way.
Millions of suns, so far, so bright,
Whisper old tales through the night.
I stand below this endless sea,
And wonder what’s beyond — for me.
This is only a sample; any original poem or short story describing the stars, constellations, the Moon, planets, or the feeling of watching the night sky is a perfectly good answer.