Chapter 17: Stars and the solar system

These NCERT Class 8 Science Chapter 17 notes explain stars and the solar system in a clear and structured manner. The chapter focuses on the universe, celestial objects and the structure of the solar system.

It discusses stars, constellations like Ursa Major and Orion, the pole star and why stars twinkle. The chapter also explains the solar system, planets in order, the moon, asteroids, comets, meteors and artificial satellites.

Chapter 17 – Stars and the Solar System is important for understanding basic astronomy and space science. It is highly relevant for school examinations and foundation level competitive preparation.

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1. Introduction: the universe

• The universe is the vast space that contains stars, planets and galaxies.
• Everything we see in the sky is part of the universe.
• The universe includes many celestial objects.
• It is extremely large and still expanding.
• Just like a village has many houses, the universe has many galaxies.

2. Celestial objects in space

• Celestial objects are natural objects found in space.
• The Sun, Moon and stars are celestial objects.
• Planets and their satellites are also celestial bodies.
• These objects move in space due to gravitational forces.
• They form part of the universe.

3. Stars and their properties

• Stars are huge balls of hot gases.
• They produce their own light and heat.
• Stars are also called luminous objects.
• The Sun is the nearest star to Earth.
• Stars appear small because they are very far away.

4. Twinkling of stars

• Stars appear to twinkle due to changes in Earth’s atmosphere.
• Their light passes through layers of air with varying density.
• These changes bend the light rays.
• Stars are very far and appear as point sources of light.
• This effect is called twinkling of stars.

5. Constellations and patterns

• A constellation is a group of stars forming a recognizable pattern.
• Constellations were used in ancient times for navigation.
• Ursa Major is also known as Saptarishi.
• Orion is another important constellation.
• Constellations help identify stars in the sky.

6. Pole star and direction

• The Pole star appears almost fixed in the sky.
• It indicates the north direction.
• It is useful for travellers to find directions.
• The Pole star lies close to Earth’s axis.
• It is part of the constellation Ursa Minor.

7. Solar system and its components

• The solar system consists of the Sun and eight planets.
• It also includes moons, asteroids, comets and meteoroids.
• All planets revolve around the Sun.
• The Sun is at the centre of the solar system.
• Gravitational force keeps the system together.

8. The Sun as source of energy

• The Sun is the centre of the solar system.
• It provides heat and light to Earth.
• It is the main source of energy for life.
• Plants use sunlight for photosynthesis.
• Without the Sun, life would not exist.

9. Planets and their movement

• Planets do not have their own light.
• They reflect light from the Sun.
• Planets move around the Sun in fixed paths called orbits.
• There are eight planets in the solar system.
• Each planet has unique features.

10. Order of planets from the Sun

• The planets in order are Mercury, Venus, Earth and Mars.
• Jupiter and Saturn follow after Mars.
• Uranus and Neptune are the outermost planets.
• A memory trick is “My Very Efficient Mother Just Served Us Noodles.”
• This helps remember the sequence easily.

11. Earth as a unique planet

• Earth has water, air and suitable temperature.
• It is known as a life-supporting planet.
• It has the right atmosphere for living beings.
• Earth revolves around the Sun and rotates on its axis.
• It is the only known planet with life.

12. The Moon and its phases

• The Moon is the natural satellite of Earth.
• It does not have its own light and reflects sunlight.
• It revolves around the Earth.
• The Moon shows different phases of moon like new moon and full moon.
• The shape of the Moon changes due to its position relative to Earth and Sun.

13. Small celestial bodies

• Asteroids are small rocky objects mainly found between Mars and Jupiter.
• Comets appear as bright objects with long tails.
• Comets move in long elliptical paths around the Sun.
• Meteoroids are small rocky pieces moving in space.
• Meteors and meteorites are related forms of meteoroids.

14. Meteoroids, meteors and meteorites

• Meteoroids are small rocky pieces present in space.
• Meteors are meteoroids that burn in Earth’s atmosphere and appear as shooting stars.
• Meteorites are meteoroids that reach Earth’s surface.
• Most meteors burn up before reaching the ground.
• These objects are part of the solar system.

15. Artificial satellites and their uses

• Artificial satellites are man-made objects that revolve around Earth.
• They are used for communication and television signals.
• They help in weather forecasting.
• Examples include INSAT and GSAT.
• Artificial satellites support modern technology.

16. Key exam-oriented keywords explained

• Universe: Vast space containing galaxies and celestial bodies.
• Celestial objects: Natural objects found in space.
• Stars: Luminous bodies producing their own light and heat.
• Constellation: Group of stars forming a pattern.
• Pole star: Star that indicates the north direction.
• Solar system: Sun and the objects that revolve around it.
• Planets: Non-luminous bodies that revolve around the Sun.
• Orbit: Fixed path in which a planet moves around the Sun.
• Moon: Natural satellite of Earth.
• Natural satellite: Celestial body that revolves around a planet.
• Asteroids: Small rocky bodies between Mars and Jupiter.
• Comets: Icy bodies with long tails moving around the Sun.
• Meteors: Burning meteoroids seen as shooting stars.
• Artificial satellites: Man-made objects revolving around Earth.

17. One-page summary for quick revision

• The universe contains stars, planets and galaxies.
• Stars are luminous, while planets reflect sunlight.
• The Sun is the centre of the solar system.
• Earth is a life-supporting planet.
• The Moon is Earth’s natural satellite.
• Asteroids, comets and meteors are small celestial bodies.

Understanding NCERT Class 8 Science Chapter 17 is essential to learn about celestial bodies and the structure of the solar system. The chapter clearly explains planets, satellites and other small bodies in space.

The concepts help students build a strong base in astronomy and scientific observation. It is highly useful for school exams and foundation competitive preparation.

Continue reading NCERT Class 8 Science Chapter 18 – Pollution of Air and Water to understand environmental issues and sustainable practices.

FAQs

Q1. What are celestial objects?
Celestial objects are natural objects found in space, such as stars, planets and moons.

Q2. Why do stars twinkle?
Stars twinkle because their light passes through Earth’s atmosphere, which keeps changing in density.

Q3. What is the solar system?
The solar system consists of the Sun, eight planets and other celestial bodies that revolve around the Sun.

Q4. What is the difference between meteors and meteorites?
Meteors are burning meteoroids seen in the sky, while meteorites are those that reach the Earth’s surface.

Q5. Why is this chapter important for exams?
It explains astronomy and solar system concepts, which are important for school exams and foundation preparation.

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