In Nubra, Ladakh, the night sky shows thousands of stars. How far away are they — and why do their patterns look so familiar?
Key idea
Stars and Constellations
Ancient people saw patterns of stars as shapes of animals, objects, or characters from stories — useful for navigation before the compass.
Orion the Hunter
Three stars form his belt. Nearby Canis Major (his dog) holds Sirius, the brightest star in the night sky.
The Pole Star
Found using the Big Dipper (Ursa Major, called Saptarishi in India). It appears almost stationary in the north, helping travellers find direction.
Key idea
Watching the Night Sky
1
Light pollution
Excessive artificial light and smoke or dust reduce the number of visible stars, especially in cities.
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Sky-mapping apps
Apps like Sky Map and Stellarium help identify stars, constellations, and planets from wherever you're standing.
Key idea
The Sun Is a Star
An extremely hot, spherical ball of gases that gives out huge amounts of energy — that's what makes it glow.
Why it looks so much bigger
The Sun is only about 100 times bigger than Earth — but it looks so much brighter than other stars simply because it's far closer to us (about 150 million km away).
Key idea
Inner (Rocky) and Outer (Gas Giant) Planets
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Inner planets
Mercury, Venus, Earth, Mars — smaller, with solid rocky surfaces.
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Outer planets
Jupiter, Saturn, Uranus, Neptune — much larger, made mostly of gas and ice, with ring-like structures.
Key idea
Venus, Mars, and Earth
Planet | Nickname | Why
Venus
Morning / Evening Star — Bright and visible near sunrise or sunset (though not actually a star)
Mars
The Red Planet — Its soil has a reddish colour
Earth
The Blue Planet — Most of its surface is covered by water
Key idea
The Moon and India's Chandrayaan Missions
1
The Moon
Earth's natural satellite, taking about 27 days to revolve around Earth. Its many craters, formed by impacts, are preserved because it has no atmosphere.
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Chandrayaan-3
Achieved a soft landing near the Moon's south pole on 23 August 2023 — now celebrated every year as National Space Day.
Key idea
Asteroids and Comets
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Asteroids
Small, rocky, irregularly shaped objects that orbit the Sun, mostly found in the asteroid belt between Mars and Jupiter.
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Comets
Icy, dusty objects with long tails, visible when close to the Sun. Halley's Comet appears every 76 years — it was last seen in 1986.
Key idea
The Milky Way and the Universe
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Solar System
The Sun, planets, moons, asteroids, and comets that orbit the Sun.
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Milky Way Galaxy
Our home galaxy (Akasha Ganga) — billions of stars, including the Sun.
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The Universe
Everything that exists — including countless galaxies beyond our own.
Chapter · Key terms to remember
Key Terms
Constellation
A region of sky with a recognizable star pattern.
Planet
A large, near-spherical object orbiting the Sun.
Satellite / Moon
An object orbiting a larger one; Earth's natural satellite.
Chapter · Key terms to remember
More Key Terms
Asteroid
A small, rocky object orbiting the Sun.
Comet
An icy object with a long tail, orbiting the Sun.
Galaxy
A huge collection of stars — ours is the Milky Way.
Chapter · Key terms to remember
More Key Terms
Revolution / Rotation
Orbiting a body / spinning on one's own axis.
Light pollution
Artificial light that hides stars from view.
Questions for your notebook
Write these down, then discuss
1
Match: (i) Satellite of Earth (ii) Red planet (iii) Constellation (iv) Planet called an evening star — with (a) Orion (b) Venus (c) Mars (d) Moon.
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Solve the riddle: my letters come from MAN (not CAN), ACE and FAN, RAT (not CAT), and SUN (not FUN). I am a planet that moves around the Sun. Then make two riddles of your own.
3
Which of these is NOT a member of our Solar System? (i) Sirius (ii) Comets (iii) Asteroids (iv) Pluto
Project as-is — students copy the questions, then the class discusses answers together.