EARTH AND SOLAR SYSTEM

our solar system ...

Our solar system is located in the Milky Way galaxy and consists of a central star, the Sun, and everything that orbits around it. The eight planets, including Earth, that orbit the Sun are Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. In addition to the planets, there are also dwarf planets such as Pluto, and numerous smaller bodies such as comets, asteroids, and meteoroids.

The Sun is the central figure of the solar system, comprising more than 99% of its total mass. It is a nearly perfect sphere of hot plasma, constantly emitting energy in the form of light and heat. The Sun's immense gravity keeps all the planets in orbit around it.

The four inner planets, Mercury, Venus, Earth, and Mars, are rocky and relatively small in size. They are also known as the terrestrial planets. Mercury is the closest planet to the Sun and has a very thin atmosphere. Venus is the hottest planet in the solar system due to its thick, toxic atmosphere that traps heat. Earth is the only planet known to harbor life, and Mars has a thin atmosphere and is believed to have had liquid water on its surface in the past.

The four outer planets, Jupiter, Saturn, Uranus, and Neptune, are much larger than the terrestrial planets and are known as gas giants. They are mostly composed of hydrogen and helium, and have thick atmospheres and no solid surfaces. Jupiter is the largest planet in the solar system and has a strong magnetic field. Saturn is known for its beautiful rings made of ice and rock particles. Uranus and Neptune are both ice giants, with a slushy mixture of water, ammonia, and methane.

Beyond Neptune lies the Kuiper Belt, a region of icy bodies and dwarf planets including Pluto. Beyond the Kuiper Belt is the Oort Cloud, a vast region of icy objects that is thought to be the source of many long-period comets.

The exploration of our solar system has been ongoing for centuries, with significant advancements in technology allowing us to learn more about our planetary neighbors. The study of our solar system has led to a greater understanding of the universe and the fundamental laws of physics that govern it.

The Earth

The earth is the third nearest planet to the sun. In

size, it is the fifth largest planet. It is slightly flattened

at the poles. That is why, its shape is described as a

Geoid. Geoid means an earth-like shape.

Conditions favourable to support life are probably

found only on the earth. The earth is neither too hot

nor too cold. It has water and air, which are very

essential for our survival. The air has life-supporting

gases like oxygen. Because of these reasons, the earth

is a unique planet in the solar system.

From the outer space, the earth appears blue

because its two-thirds surface is covered by water. It

is, therefore, called a blue planet.

The Moon

Our earth has only one

satellite, that is, the

moon. Its diametre is

only one-quarter that of

the earth. It appears so

big because it is nearer to

our planet than other

celestial bodies. It is

about 3,84,400 km away

from us. Now you can

compare the distance of

the earth from the sun

and that from the moon.

The moon moves around the earth in about 27 days.

It takes exactly the same time to complete one spin. As

a result, only one side of the moon is visible to us on

the earth.

The moon does not have conditions favourable for

life. It has mountains, plains and depressions on itssurface. These cast shadows on the moon’s surface.

Look at the full moon and observe these shadows.

Asteroids

Apart from the stars, planets and satellites, there are

numerous tiny bodies which also move around the

sun. These bodies are called asteroids. They are found

between the orbits of Mars and Jupiter (Figure 1.2).

Scientists are of the view that asteroids are parts of a

planet which exploded many years back.

Meteoroids

The small pieces of rocks which move around the sun

are called meteoroids. Sometimes these meteoroids

come near the earth and tend to drop upon it. During

this process due to friction with the air they get heated

up and burn. It causes a flash of light. Sometimes, a

meteor without being completely burnt, falls on the

earth and creates a hollow.

Do you see a whitish broad band, like a white

glowing path across the sky on a clear starry night? It

is a cluster of millions of stars. This band is the Milky

Way galaxy (Figure 1.6). Our solar system is a part of

this galaxy. In ancient India, it was imagined to be a

river of light flowing in the sky. Thus, it was named

Akash Ganga. A galaxy is a huge system of billions of

stars, and clouds of dust

and gases. There are

millions of such galaxies

that make the Universe.

It is difficult to imagine

how big the universe is.

Scientists are still trying

to find out more and more

about it. We are not

certain about its size but

we know that all of us –

you and I belong to this

universe.