Keywords for Chapter 4 of Science Class 6:

1. Solar system
2. Planets
3. Revolving and rotating
4. Orbit
5. Gravity
6. Asteroids
7. Meteoroids
8. Comets
9. Artificial satellites

Explanation:

Solar system:
A solar system is a collection of planets, their moons, comets, asteroids, and other celestial bodies that orbit around a star called the Sun.

Planets:
Planets are large celestial bodies that revolve around the Sun in elliptical orbits. There are eight planets in our solar system, namely Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Revolving and rotating:
Planets not only revolve around the Sun but also rotate on their own axis. The time taken by a planet to complete one rotation on its axis is called a day, and the time taken to complete one revolution around the Sun is called a year.

Orbit:
The path followed by a planet around the Sun is called its orbit. The shape of the orbit is not perfect, and it is elliptical in shape.

Gravity:
Gravity is the force that attracts all objects in the universe towards each other. The force of gravity between two objects depends on their mass and the distance between them.

Asteroids:
Asteroids are small, rocky celestial bodies that orbit around the Sun. They are also called minor planets.

Meteoroids:
Meteoroids are small rocks or particles that float in space. When a meteoroid enters the Earth's atmosphere, it is called a meteor.

Comets:
Comets are celestial bodies made up of ice, dust, and rock. When a comet comes close to the Sun, the heat causes the ice to melt and release gas and dust particles. This creates a glowing tail that can be seen from Earth.

Artificial satellites:
Artificial satellites are man-made objects that are launched into space to orbit around the Earth. They are used for communication, weather forecasting, navigation, and scientific research.

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