Ans: A satellite is a solid heavenly body that revolves around a planet.
2. What are artificial satellites?
Ans: The man-made satellites which keep revolving around the earth are called artificial satellites.
3. What is one light year?
Ans: The distance travelled by light in one year is called one light year.
4. Show that one light year is 9.46 × 1015m.
Ans: One light year is the distance travelled by the light in 365.25 days.
1 year = 365.25 days
1 day = 24 hours
1 hour = 60 minutes
1 minute = 60 seconds
1 year = 365.25 × 24 × 60 × 60 seconds = 31557600 seconds
Now, we know that,
Distance = velocity × time
= 3 × 108 × 31557600
= 9.46 × 1015 m
Hence, one light year is 9.46 × 1015m.
5. What are comets?
Ans: Comets are small objects that appear occasionally in the sky having a head and a luminous tail.
6. What is a comet? Describe the structure of the comet with a diagram.
Ans: The gaseous mass that revolves around the sun in highly elliptical path is called comet. It is made up of frozen gas, dust and ice. A comet consists of three main parts, the nucleus, the coma and the tail. The nucleus consists of crumbly rock particles trapped inside a frozen matter. When the comet approaches the sun, the outer layer of the nucleus begin to evaporate and it is called coma. The coma and the nucleus together are called head of the comet. As the comet approaches nearer to the sun, pressure from the solar wind elongates the coma into one or more tails.
7. What are asteroids?
Ans: The minor planets revolving around the sun in the asteroid belt between the orbits of Mars and Jupiter are called asteroids.
8. Define satellite.
Ans: A satellite is a solid heavenly body that revolves around a planet.
9. What are artificial satellites?
Ans: The man-made satellites which keep revolving around the earth are called artificial satellites.
10. What is artificial satellite? Mention any two reasons for lunching artificial satellites into the space.
Ans: Moon is the natural satellite of earth.
Manmade satellites are known as an artificial satellite.
The two reasons for launching artificial satellites into space are:
a. Weather forecast, research
b. Telecommunication
11. Mention any three reasons for launching artificial satellites in space.
Ans: The reasons for launching artificial satellites in space are:
a. To collect more and reliable information about solar system, stars, nebulas and galaxies.
b. To research the life in outer space.
c. To investigate different military and spying operation of enemies.
12. What are stars?
Ans: Stars are celestial bodies, consisting of a large, self-luminous mass of hot gas held together by their own gravity.
13. What is pulsar?
Ans: The star which revolves faster and radiates radio waves is called pulsar.
14. What is a red giant star?
Ans: A red giant star is a star with a mass like our sun that is in the last phase of its life.
15. Define supernova star.
Ans: If the mass of red giant is more than five solar masses then the difference in pressure and temperature between the core and the outer shell makes the star to explode, at this stage, it is called supernova star.
16. What is galaxy?
Ans: Galaxy is a giant assembly of billions of stars, interstellar gas and dust particles forming their own cluster in the universe all held together by gravity.
17. Write any two differences between constellation and galaxy.
Ans:
The two differences between constellation and galaxy are:
| Constellation | Galaxy |
| 1. A group of stars with the definite pattern seen in the night sky is a constellation. | 1. A collection of trillions of stars, gases and dust particles is called a galaxy. |
| 2. 88 constellations have been discovered so far. Eg: Ursa Major | 2. There are about one hundred billion galaxies in the observable universe. Eg: The Milky Way |
18. What is galaxy? Classify the galaxy on the basis of shape and explain about them.
Ans: The system of stars, star clusters, nebula, dust and gas which are held together by gravity is called galaxy. There are about 1012 galaxies in the universe. On the basis of the shape, galaxies are classified into irregular, spiral and elliptical galaxies.
a. Irregular galaxies
Irregular galaxies have stars in a random device by the pattern. They are the youngest galaxies. They have formed about 13.5 billion years ago. NGC 6822 and IC 1613 are the examples of irregular galaxies.
b. Spiral galaxies
Spiral galaxies are spring-shaped. They have a nucleus of bright stars and flattered arms that spiral around the nucleus. The spiral arms contain millions of stars. The Milky Way galaxy is the example of a spiral galaxy.
c. Elliptical galaxies
Elliptical galaxies are egg-shaped found largely in galaxy clusters. They contain older stars of low masses. Messier 87, Fornax and Sculptor are some examples of elliptical galaxies.
19. Define constellation.
Ans: The group of stars having a specific shape is called a constellation.
20. Write any three advantages of studying constellation.
Ans: Three advantage of studying constellation are,
a. It helps to estimate the time of night.
b. It helps scientist for dividing the sky into regions.
c. It helps in grouping the stars in the night sky.
21. Write any three superstitions related to zodiacs.
Ans: The superstitions related to zodiacs are:
a. It is believed that the attitude of a person will be accordingly the nature of their zodiac.
b. Some people select a particular day for travelling and initiating some important tasks on the basis of the position of the moon on the certain zodiac.
c. Many people prefer certain gems to put on accordingly as their zodiac or astrologist prescription, but there is no scientific reason behind it.
22. Write any three importance of zodiacs.
Ans: The importance of zodiacs are given below:
a. Some people can easily guess time and direction they want to know by observing the position of zodiacs.
b. Zodiacs are used to predict love-life, fortune, and health of people.
c. Zodiac is a great tool for better understanding the motions of the sun, the earth and the other planets.
23. Write short notes on:
a. Ursa major
b. Orion
Ans: a. Ursa majorb. Orion
Ursa Major is a constellation. It has seven stars. It is a group of seven bright stars. The constellation is identified by its question mark shape. It is the third large constellation which can be seen in April in the northern part of the sky.
b. Orion
Orion is a constellation. There are seven stars in this constellation. It looks like a hunter. It can be seen in the sky during the months of January and February in the middle sky of the northern hemisphere.
24. Life is not possible on Mars though it contains water, oxygen and carbon dioxide, gives a reason. Categorize the following heavenly bodies in term of planet, satellite, asteroids or comet:
a. Temple Tuttle
b. Sirius
c. Ursa-major
d. Neptune
Ans: b. Sirius
c. Ursa-major
d. Neptune
a. Temple Tuttle-Comet
b. Sirius -Star
c. Ursa-major - Constellation
d. Neptune - Planet
The life not possible on Mars though it contains water, oxygen and carbon dioxide because of the following reasons:
i. It has a thin atmosphere which allows radiation from the sun to irradiate the surface of the planet.
ii. It is dry and barren because most of its water is locked up in the polar ice caps.
25. What is solar system?
Ans: The family of the sun which includes eight planets, their satellites, meteors, meteorites, comets, asteroids, etc. that move around the sun is called the solar system.
26. What is a planet?
Ans: A relatively small, solid celestial body moving in orbit around a star, particularly the sun is called a planet.
27. What are inner planets?
Ans: The planets which are nearer to the sun and separated from the rest of the planets by asteroid belt are called inner planets.
28. What are outer planets?
Ans: The planets which are far away from the sun and lying beyond the asteroid belt are called outer planets.
29. Mention any three application of studying the solar system.
Ans: The applications of studying solar system are:
a. It helps to estimate the distance between the planets.
b. It helps to predict the occurrence of the solar and lunar eclipse on the earth.
c. It helps to estimate the duration of the rotation and the revolution of the planets.
30. Write any three reasons for the omission of Pluto from the list of the planet in the solar system.
Ans: The Pluto has been omitted from the list of the planet in the solar system because of the following reasons:
a. Its orbit does not lie on the same plane of the orbit of the other planets.
b. It intersects the orbit of Neptune.
It is very small and very far from the sun.
31. Write any three reasons for the existence of living beings on the earth.
Ans: The reasons for the existence of living beings on the earth are:
a. The earth is at a suitable distance from the sun.
b. The earth has atmosphere and all the gases required for the life of creatures.
c. The earth has water which is the most important chemical necessary for life.
32. Write any three features of the planet Saturn.
Ans: The features of the planet Saturn are:
a. It has a brightest concentric ring which is made up of ice, dust particles which revolves around it.
b. It is the second largest planet in the solar system.
c. It has 23 satellites.
33. Describe in brief about the structure and shape of the solar system with diagram.
Ans: The celestial bodies including planets, satellites, comets, etc. which revolve around the sun form the solar system. It consists of eight planets their satellites, heavenly bodies like a meteor, meteorites, plasma, asteroids, comets, charged particles and dust particles. All the member of the solar family revolves around the sun in their orbit due to the gravitational attraction between the sun and the other bodies. Asteroids are also found in the solar system and they are concentrated between the orbits of the Mars and Jupiter. The four planets i.e. Mercury, Venus, Earth and Mars are inner planets.
34. Write short notes on:
a. Mercury
b. Mars
Ans: a. Mercuryb. Mars
Mercury is the closest planet to the sun. It takes about 59 days to complete one rotation on its axis and 88 days to complete one revolution around the sun. It does not have atmosphere and satellite. Its temperature varies from -170°C to 427°C. The diameter of the Mercury is 4880 km. The phases of the Mercury can be seen by using a telescope.
b. Mars
Mars is the fourth nearest planet from the sun. Due to the presence of limonite, it is red in colour. So, it is called red planet and can be seen easily from the earth. It takes 24 hr 37 min to complete one rotation and 687 days to complete one revolution around the sun. Its diameter is 6,742km. It consists of two satellites. They are diemos and phobos.
35. What is a satellite? Mention its types and explain.
Ans:
A satellite is a heavenly body that revolves around the planet in their own orbit. They do not have their own light. They reflect the light rays coming from the sun.
There are two different types of satellites. They are natural satellite and artificial satellite.
a. Natural satellite
Natural satellites are those members of the solar system which revolve around the planets in their elliptical orbits. They do not have their own light. They reflect the light from the sun. They are called the moon.
b. Artificial satellite
The satellite that is made on the earth which continuously revolves around the earth or other heavenly body is called an artificial satellite. The orbit of artificial satellites is elliptical and characterized by three parameters apogee, perigee and inclination.
36. What is solar wind? Mention any three features of the sun.
Ans: The solar wind is a stream of energized, charged particles, primarily electrons and protons, flowing outward from the sun. It is caused by the hot solar corona, which is the outermost layer of the solar atmosphere.
The features of the sun are given below:
i. The sun is the medium-sized star whose diameter is about 1,392,000 km.
ii. The sun’s mass consists of about 75% of hydrogen and about 25% of helium.
iii. The sun produces most of the energy in the core by the means of nuclear fusion.
37. What is a black hole?
Ans: A black hole is a heavenly body or point in space which has infinite density and gravity such that even light falling on it can’t escape.
38. Define meteorites.
Ans: The meteor which reaches the earth’s surface before they completely burn is called meteorites.
39. What are meteors?
Ans: Meteors are the bright streak of light seen for a short duration of time in the sky on a clear night.
40. Define meteorites.
Ans: The unburned masses of the meteors that reach the earth’s surface are called meteorites.
41. Define stony meteorites.
Ans: The meteorites which contain more silica and less iron and magnesium are called stony meteorites.
42. Write short notes on meteor and meteorites and write the types of meteorite.
Ans:
Meteor: A meteor is a bright streak of light seen for a short duration in the sky on a clear night. It is also called shooting star or falling star because it looks like a star falling from one direction to the other direction to the other in the sky.
Meteorites: Some meteors are larger and do not burn completely as they travel through the atmosphere and reach the surface of the planets or moon due to gravity. These are called meteorites. On the basis of the nature of particles present in the meteorites, they are of three types. They are:
i. Stony: That meteorite which consists of more amounts of silica and less amount of iron is called stony meteorites.
ii. Irony: That meteorite which consists of more amounts of iron and less amount of silica is irony meteorites.
iii. Stony-iron: Those meteorites which consist of an equal amount of iron and silica is called stony-iron meteorites.
43. Describe in brief about Milky Way galaxy.
Ans: The Milky Way galaxy is a spiral galaxy that contains our solar system. The main body of this galaxy is a disc-like shape. Its central part is thicker and its edge is thinner. It is about 2.5 × 104light years away from the galactic centre. It is estimated that there might be 1011 stars in the Milky Way galaxy and its total mass is about 1.33 × 1011 times more than that of the sun.