CHAPTER- 12 BEYOND EARTH
Notes
1. In ancient times, certain prominent stars in the clear sky served as directional guides for caravans traveling through Nubra.
2. Stars shine with their own light.
3. Identifying stars and their patterns was a useful skill for travelers in ancient times.
4. In ancient times, the patterns of groups of stars were called constellations.
- In the first half of the twentieth century, the International Astronomical Union (IAU) defined the boundaries of constellations by international agreement.
- Officially, 88 constellations have been listed.
- The constellation Orion is often depicted as a hunter. The three stars located at the center of this constellation are known as the hunter’s belt.
- The star Lubdhak (Sirius) of the Canis Major constellation is the brightest star in the night sky.
5. Pole Star (Polaris)— The Pole Star appears stationary in the northern direction, with the help of which the north direction can be identified in the Northern Hemisphere.
6. Sun— It is a star; it is an extremely hot sphere of gases.
- The Sun produces heat and light, which are the primary sources of energy on Earth.
- In diameter, it is about 100 times larger than the Earth.
- The distance from the Earth to the Sun is approximately 150 million kilometers.
7. Revolution— The movement of a body around the Sun is called revolution.
8. Planet— A planet is a large and nearly spherical body that revolves around the Sun.
- The Earth is also a planet, and it takes approximately one year for the Earth to complete one revolution around the Sun.
- In order of increasing distance from the Sun, the eight planets of the solar system are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
- The four inner planets closest to the Sun are Mercury, Venus, Earth, and Mars. All four are small in size, and their surfaces are solid and rocky.
- A large part of the Earth’s surface is covered with water; therefore, it appears blue when seen from space. For this reason, the Earth is also called the Blue Planet.
- Mars is called the Red Planet because the soil on Mars is red in color.
- The four outermost planets are Jupiter, Saturn, Uranus, and Neptune.
9. Telescope— It helps us observe many faint celestial objects that cannot be seen with the naked eye without any instruments.
10. Natural satellites— The bodies that revolve around planets are generally called satellites. They are smaller in size compared to planets.
- The natural satellites of planets are called moons.
- The Earth has one moon, while Mars has two moons. Jupiter, Saturn, Uranus, and Neptune have many moons.
11. Moon— The Moon, Earth’s natural satellite, takes about 27 days to complete one revolution around the Earth.
- The diameter of the Moon is about one-fourth of the Earth’s diameter.
- On the surface of the Moon, circular bowl-shaped structures are visible, which are called craters.
- India has completed three Chandrayaan missions for the study of the Moon, and preparations for the fourth mission are underway.
- India’s first mission to the Moon, Chandrayaan-1, was launched in the year 2008.
- The second mission, Chandrayaan-2, was sent in 2019.
- Under the third mission, Chandrayaan-3 was launched in July 2023.
12. Asteroids— In the solar system, there are many small bodies that are rocky and irregular in shape; these are called asteroids.
- Many asteroids revolve around the Sun in their own orbits between the orbits of Mars and Jupiter; this region is called the asteroid belt.
13. Comets— Sometimes, some visitor bodies come into our solar system from the outer regions of the solar system. These bodies, which have long tails, are called comets.
- They are made up of dust, gases, rock fragments, and ice.
14. Solar System— The Sun, eight planets, their satellites, and many relatively small bodies including asteroids and comets together are called the solar system.
15. Milky Way Galaxy— A galaxy contains millions to billions of stars. Our solar system is a part of the Milky Way galaxy.
LET US ENHANCE OUR LEARNING
Question-1. Match the column:
Answer-
Question- 2. (1) Solve the following riddle.
My first alphabet is in MAN but not in CAN
My second alphabet is in ACE and also in FAN
My third alphabet is in RAT and not in CAT
My fourth alphabet is in SUN but not in FUN
I am a planet that moves around the sun.
(2) Make two similar riddles by yourself.
Answer- (1) Mars
(2) Two similar riddles-
a) My first alphabet is in VAN but not in CAN
My second alphabet is in EAT but not in BAT
MY third alphabet is in NEAR but not in FEAR
My fourth alphabet is in UNIFORM but not in CONFIRM
My fifth alphabet is in SUN but not in FUN
I am neither very close to the sun nor very far from it.
Answer is- Venus
b) My first alphabet is in NUT but not in HUT
My second alphabet is in EARN but not in TURN
My third alphabet is in POEM but not in TOM
My fourth alphabet is in TONE but not in CONE
My fifth alphabet is in US but not in BUS
My sixth alphabet is in NOT but not in HOT
My seventh alphabet is in ELIGHT but not in DELIGHT
Answer is- Neptune
Question- 3. Which of the following is not a member of our Solar system?
(1) Sirius (2) Comets (3) Asteroids (4) Pluto
Answer- (a) Sirius
Question- 4. Which of the following is not a planet of the sun?
(1) Jupiter (2) Pluto (3) Neptune (4) Saturn
Answer- (b) Pluto
Question- 5. Which is the brighter star, the pole Star or Sirius?
Answer- Among Pole Star (Polaris) and Lubdhak (Sirius), Lubdhak is brighter. Lubdhak is considered the brightest star in the night sky.
Question- 6. An artist's representation of the solar system is given in Fig. 12.12. Is the order of the planets correct? If not, write the correct order in the boxes in the figure.
Answer-
In the picture, the correct order of the solar system should be:
1. Mercury, 2. Venus, 3. Earth, 4. Mars, 5. Jupiter, 6. Saturn, 7. Uranus, 8. Neptune.
Question- 7. A portion of night sky with stars is shown in Fig. 12.13. Look carefully and identify the groups of stars that form the patterns- the big Dipper and the Little Dipper. Draw lines to connect the stars for these patterns and label them. Also, identify and label the pole star. You may refer to Fig. 12.4 for help.
Answer- The Pole Star (Polaris) is the last star of the Little Dipper. This star always remains in the northern direction. To connect these stars, we need to join them while keeping in mind the shapes of the Big Dipper and the Little Dipper. To identify the Pole Star, look at the last star of the handle of the Little Dipper and label it as the Pole Star.
Big Dipper— This constellation is made up of seven stars. Four of these stars form the shape of a large ladle or bowl, while the remaining three stars form the shape of the handle.
Little Dipper— This constellation also consists of seven stars. Its shape is similar to that of the Big Dipper, but it is smaller and less bright. The last star of this constellation is the Pole Star.
Question- 8. A portion of the night sky is shown in Fig. 12.14. Draw lines to connect the stars for Orion and label the star Sirius. You may refer to Fig. 12.3. Answer- In this picture, the Orion constellation and the Lubdhak (Canis Major) constellation are shown. The stars are connected with lines and their names are written.
Question- 9. You can see stars fading away at down and appearing at dusk. During the day we do not see the stars. Explain why.
Answer- Stars disappear at dawn and appear in the evening because during the daytime the Sun’s bright light is very strong, which hides the light of the stars. Due to this intense sunlight, stars are not visible, and as night approaches, the light of the stars becomes visible again.
Question- 10. During a clear night, try to observe the big Dipper 3-4 times at an interval of 2 to 3 hours. Also try to locate the pole star each time. Does the big Dipper appear to move? Draw a rough sketch to illustrate this, mentioning the time in each case.
Answer- When observing the Big Dipper (Saptarshi) constellation, it appears that this constellation slowly changes its position in the night sky. This change occurs due to the rotation of the Earth. If we observe it at intervals of 2–3 hours, we see that Saptarshi gradually moves from west to east, while the Pole Star remains fixed in its position.
First observation – 8:00 PM: Saptarshi is in the northern direction, and the Pole Star is almost at the same position.
Second observation – 10:00 PM: Saptarshi appears to have moved slightly forward, but the Pole Star is still in the same place.
Third observation – 12:00 AM: By this time, Saptarshi has moved further ahead, and the Pole Star is still at the same position.
Question- 11. Think about the night sky and write a poem or a story on it.
Answer- Poem about the Night Sky-
In the night sky, stars twinkle bright,
Like golden dreams arriving in sight.
The Pole Star stands still, showing the way,
Teaching us always Saptarshi’s play.
Moonlight dances with the stars above,
Singing songs of light in darkness and love.
The silence of night softly has a say,
Weaving a new story in each star’s ray.
Story about the Night Sky-
The silence of the night had spread all around, and a young boy was watching the stars from the roof of his house. His grandmother had told him that every star tells a story. One night, when the Moon was shining in all its glory, he noticed that the Saptarshi constellation was slowly changing its position. But he observed that the Pole Star was still in the same place, meaning the star remained stationary. That night, he decided that when he grew up, he would become a great scholar of stars (Astronomer).
