The Solar System Chapter Notes | Natural World for PAT PDF Download

Introduction

We live on a planet called Earth, which is a special place because it has life. Earth is part of a big group called the solar system, which has the sun, eight planets, and many other things like moons and stars. The solar system is inside an even bigger group called the Milky Way galaxy, which has lots of stars. All the stars, planets, and galaxies together make the universe, which is everything that exists in space.

The Milky Way Galaxy

• A galaxy is a big group of stars, gas, dust, and other space things held together in the center.
• There are many galaxies in the universe, like Andromeda, Black Eye, and Whirlpool.
• Earth is part of the Milky Way galaxy.
• All the stars we see in the night sky are part of the Milky Way galaxy.
• The Milky Way looks like a hazy, faint band of light stretching across the night sky.
• The Milky Way has the sun, moon, stars, planets, comets, and asteroids.

Stars

• Stars are big balls of fire that give their own light and heat.
• The sun is a star in the Milky Way galaxy.
• Many stars are much bigger than the sun, but they look small because they are very far from Earth.
• Some stars in the sky look like groups or patterns called constellations.
• Two famous constellations are Ursa Major and Ursa Minor.

Fun Fact

Constellations helped farmers long ago to know the right time for planting and collecting crops.

The Solar System

The solar system has the sun, eight planets, their moons, comets, and asteroids. The word "solar" means something that belongs to the sun.

The Sun

• The sun is a star and the closest star to Earth.
• The sun gives its own light and heat.
• The sun is the center of the solar system.
• All the planets move around the sun in an oval-shaped path called an elliptical orbit.
• An orbit is the path that space objects follow when they move.

Satellites or Moons

• Satellites are space objects that move around planets and are also called moons.
• Moons do not have their own light; they reflect the sun's light.
• The moon we see shining in the night sky from Earth is our natural satellite.

Planets

• Planets are space objects that move around the sun in an orbit.
• Planets do not make their own heat or light; they reflect the sun's light.
• The eight planets in our solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
• Planets closer to the sun have smaller orbits, and planets farther from the sun have longer orbits.

Mercury

• Mercury is the smallest planet in the solar system.
• Mercury is the closest planet to the sun, so it is very hot.
• It takes 88 days for Mercury to travel around the sun.
• Mercury has no moon or satellite.

Venus

• Venus is called the twin planet of Earth because it is almost the same size as Earth.
• Venus is the brightest and hottest planet in the solar system.
• Venus is also called the morning star and evening star because we can see it just before sunrise or just after sunset.
• Venus has no moon.

Earth

• Earth is the third planet from the sun.
• Earth is the most suitable planet for life because it has water and air.
• Two-thirds of Earth's surface is covered with water, so it is also called the blue planet.
• It takes 365 days for Earth to travel around the sun.
• Earth has one moon.

Mars

• Mars is called the red planet because of its red color.
• Mars is the fourth planet from the sun.
• Mars has two moons.

Jupiter

• Jupiter is the largest planet in the solar system.
• Jupiter is the fifth planet from the sun.
• Jupiter has faint rings made of dust.
• Jupiter has 69 known moons.

Saturn

• Saturn is called the ringed planet because it has many bright rings around it.
• Saturn is the sixth planet from the sun.
• The rings of Saturn are made of dust, rocks, and ice.
• Saturn is as big as Jupiter.
• Saturn has 62 known moons.

Uranus

• Uranus is the seventh planet from the sun.
• Uranus rolls on its side, while other planets spin upright.
• Uranus has rings, but they are thin.
• Uranus has 27 known moons.

Fun Fact

Uranus bends on its side, so its rings are vertical, not horizontal.

Neptune

• Neptune is the eighth and farthest planet from the sun.
• It takes 165 years for Neptune to travel around the sun.
• Neptune has faint rings made of small particles of rocks and ice.
• Neptune has 14 known moons.

Fun Fact

Pluto was considered the ninth planet in the solar system a long time ago. Scientists later realized Pluto is too small to be called a planet. Since September 2006, Pluto has been called a dwarf planet.

Comets

• Comets are lumps of ice and dust that travel around the sun.
• When a comet gets close to the sun, some of its frozen gases turn into vapor, making a tail of dust and ice.
• We can see the tail of a comet from Earth.

Asteroids

• Asteroids are small rocky objects that orbit around the sun.
• Most asteroids are found between Mars and Jupiter.
• Asteroids are smaller than planets but are also called planetoids.

Points To Remember

• A galaxy is a massive group of hundreds and millions of stars and other space objects held together.
• Our solar system is a small part of the Milky Way galaxy.
• Stars are big balls of fire that have their own light and heat.
• The sun and the planets, along with their satellites, comets, and asteroids, form the solar system.
• Our solar system has eight planets that move around the sun on a path called an orbit.
• Earth is the third planet from the sun and the only planet that has life on it.
• Satellites are space objects that orbit around planets.

Glossary

• Cluster: Collection
• Lump: A chunk or a piece without any definite shape