Chapter 17 Stars and The Solar System

(c) A constellation

A constellation is not a member of the solar system. Group of stars with a recognizable pattern in the sky are called as constellation.

(a) Sirius

Sirius is a planet of the sun. It is not a star.

(a) We can see only that part of the moon which reflects light towards us.

Moon does not have its own light. When sunlight falling of then it gets reflected towards us. So, only that part of the moon appear to us which reflects the light of sun towards us.

(a) Neptune

Neptune is present far away from the sun.

(b) Mars

Because on Mars, a lot of rocks and iron parts are present, when they come in contact of air, they get oxidized and turn into reddish colour.

(c) Constellation

Constellation is a group of stars with a recognizable pattern in the sky.

(d) Satellite

Satellite gives scientific information about the planet and it is a source of communication also.

(e) Stars

They are actually not stars, they are meteors.

(f) Mars, Jupiter

Asteroids occupy a large gap between the orbits of Mars and Jupiter.

(a) False

This statement is false because stars are not the member of the solar system.

(b) True

This statement is true because the smallest planet of the solar system is Mercury.

(c) False

This statement is false because Neptune is the farthest planet of the solar system.

(d) True

Yes, it is an artificial satellite. It is man- made satellite. Hence, this statement is true.

(e) False

This statement is false because there are eight planets in our solar system.

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

(f) False

This statement is false because constellation Orion is large enough to see with naked eyes.

A                                                  B

(i) Inner planets                    (a) Saturn

(ii) Outer planets                  (b) Pole star

(iii) Constellation                  (c) Great Bear, (f) Orion

(iv) Satellite of the Earth      (d) Moon

Venus become visible after sunset that is why it is called evening star. It appears in the west direction.

Jupiter is the largest planet of the solar system.

Constellation: The stars forming a group that has a recognizable shape or pattern in the sky is called constellation. For example: Great bear (Ursa Major), Orion etc. 

(a) In Ursa major, for stars are present in the bowl and the three stars in the handle. It appears like a big dipper.

(b) Orion: It appears like a hunter. In this, five stars are arranged in a form of quadrilateral and three stars appears in the belt.

Asteroids and meteors are the two objects other than planets which are the member of the solar system.

1. Asteroids: It is a collection of gases, dirt and small objects which are revolving around the sun. In between the orbits of Mars and Jupiter, asteroids occupies an large gap. Asteroids are celestial objects not planets.
2. Meteors: These are small celestial objects that can be seen as a bright streaks of light in the sky. Because of the heat produced by friction, meteors are burnt out when they enters into the earth’s atmosphere. This may lead to a bright streaks in the sky. Hence, we can say that they are not planets.  

Look at the two stars at the end of the Ursa Major. Imagine a straight line passing through these stars. Extend this imaginary line towards the north direction. At the point where the imaginary line meets to a star is called the pole star.

No, all the stars in the sky do not move. They only appear to move. This is because earth moves from west to east. Like when we travel in the train, the nearby trees and building appears to move in the backward direction.

Stars at a distance of millions of kilometers from the earth. Thus, there large distance are expressed in the light year. One light year is the distance travelled in one year.

One light year = 9.46 x 10¹² km.

If a star is located eight years away from the earth that means the distance between the star and the earth is equal to the distance which is travelled by light in eight years. So, the distance between the star and the earth us given by:

8 x (9.46 x 10¹²) km = 7.6 x 10¹² km.

Position of Mars, Venus, Uranus and Neptune should be interchanged. The correct position of the planets are as follows:

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.