1. Components Of Solar System-
Figure 01- Solar system
ü The phases of the moon occur because we can see only that part of the moon which reflects the light of the Sun towards us.
ü Stars are celestial bodies that emit light of their own. Our sun is also a star.
ü It is convenient to express distances of stars in light years.
ü Stars appear to move from east to west.
ü The pole star appears to be stationary from the Earth, because it is situated close to the direction of the axis of rotation of the Earth.
ü Constellations are groups of stars that appear to form recognizable shapes.
ü The solar system consists of eight planets and host of asteroids, comets and meteors.
ü A body revolving around another body is called a satellite.
ü Moon is the natural satellite of the Earth. Some planets also have natural satellites.
ü Venus is the brightest planet in the night sky.
ü Jupiter is the largest planet of the solar system.
ü The artificial satellites revolve around the Earth. They are much closer than the moon.
ü Artificial satellites are used for weather forecasting, long distance communication and remote sensing.
2. Sun-
ü It is the source of almost all energy on Earth. It continuously emits huge amounts of heat and light.
3. Planets-
ü A planet has a definite path in which it revolves around the sun called orbit.
ü Time taken by a planet to complete one revolution increases as the distance from the sun increases.
ü There are eight planets in our solar system: Mercury, Venus, Earth, Mars, Jupitar, Saturn, Uranus, Neptune.
4. Other Members In Our Solar System-
ü Asteroids- These are rocky planetary bits orbiting around sun. asteroid belt lies between Mars and Jupiter.
ü Comets- These are heavenly bodies that revolve around the sun. It appears generally as a bright head with a long tail.
ü Meteors and Meteorites- Meteor is a brief streak of light in the night sky caused by a meteoroid. Small meteors melt and burn up creating streaks of light. Few meteoroids which survive as they pass through the Earth’s atmosphere and reach the Earth surface are called meteorites.
ü Artificial Satellites- Man-made objects sent into space to orbit the earth. For example, IRS, EDUSAT, INSAR.
ü Constellations- A group of stars forming some kind of recognizable figures or patterns are known as constellations. Constellations appear to move from east to west as Earth rotates from west to east. Orion- the Hunter, Ursa Major- the Great Bear or Saptarishi, Cassiopeia are some constellations.
NCERT PRACTICE QUESTIONS
1. Which of the following is NOT a member of the solar system?
(a) An asteroid (b) A satellite (c) A constellation (d) A comet
Ans.- (c) A constellation
2. Which of the following is NOT a planet of the sun?
(a) Sirius (b) Mercury (c) Saturn (d) Earth
Ans.- (a) Sirius
3. Phases of the moon occur because
(a) we can see only that part of the moon which reflects light towards us.
(b) our distance from the moon keeps changing.
(c) the shadow of the Earth covers only a part of the moon’s surface.
(d) the thickness of the moon’s atmosphere is not constant.
Ans.- (a) we can see only that part of the moon which reflects light towards us.
4. Fill in the blanks.
(a) The planet which is farthest from the Sun is ____________ .
(b) The planet which appears reddish in colour is ____________ .
(c) A group of stars that appear to form a pattern in the sky is known as a ____________ .
(d) A celestial body that revolves around a planet is known as __________.
(e) Shooting stars are actually not ____________.
(f) Asteroids are found between the orbits of _________ and _________ .
Ans.- (a) Neptune. (b) Mars. (c) Constellation. (d) satellite. (e) stars. (f) Mars and Jupiter .
5. Mark the following statements as true (T) or false (F).
(a) Pole star is a member of the solar system. ( )
(b) Mercury is the smallest planet of the solar system. ( )
(c) Uranus is the farthest planet in the solar system. ( )
(d) INSAT is an artificial satellite. ( )
(e) There are nine planets in the solar system. ( )
(f) Constellation Orion can be seen only with a telescope. ( )
Ans.- (a) False (b) True (c) False (d) True (e) False (f) False
6. Match items in column A with one or more items in column B.
Ans.-
A | B |
(i) Inner planets | (g) Mars, (e) Earth |
(ii) Outer planets | (a) Saturn |
(iii) Constellation | (c) Great Bear, Orion |
(iv) Satellite of the Earth | (d) Moon |
7. In which part of the sky can you find Venus if it is visible as an evening star?
Ans.- The planet Venus is found in the western part of the sky after sunset and is said to be known as an evening star.
8. Name the largest planet of the solar system.
Ans.- Jupiter is the largest planet of the solar system.
9. What is a constellation? Name any two constellations.
Ans.- The group of stars that forms a recognizable pattern in the sky is known as a constellation. Two constellations are; Ursa Major and Orion
10. Draw sketches to show the relative positions of prominent stars in (a) Ursa Major and (b) Orion
Ans.- a) Orion seems to be like a hunter. The three bright stars appear in the belt, while five bright stars are arranged in the form of a quadrilateral. b) Ursa Major seems to be like a big dipper. There are four stars in the bowl of the dipper and three bright stars in the handle.
11. Name two objects other than planets which are members of the solar system.
Ans.- a) Meteors- Meteors are small celestial objects that are seen as bright streaks of light in the sky. Due to the heat produced by the friction of the Earth’s atmosphere, the Meteors are burnt out while entering in, this causes the bright streaks in the sky. They are not planets.
b) Asteroids- The Asteroids are the collection of a huge number of small objects; gasses and dust revolving around the sun. Between the orbits of Mars and Jupiter, they occupy the large gap. These are not planets. They are the celestial bodies and are known as Asteroids.
12. Explain how you can locate the Pole Star with the help of Ursa Major.
Ans.- For locating, the pole stars in the sky, first the big dropper or the Ursa Major constellation must be found . The bowl of the big dipper consists of the four bright stars.
13. Do all the stars in the sky move? Explain.
Ans.- No, the earth rotates on its axis from west to east. Therefore, all the stars in the sky seem to move from east to west. With reference to Earth, pole star in the sky does not seem to move because it is located above the axis of rotation of the Earth in the north direction. It seems to remain stationary at a point in the sky.
14. Why is the distance between stars expressed in light years? What do you understand by the statement that a star is eight light-years away from the Earth?
Ans.- The distance of the star from the earth and the distance between the stars are very huge. It is troublesome to express this distance in kilometre (km). Therefore, these huge distances are expressed in light-years. One light-year is equal to the distance travelled by the light in one single year. One light-year is equal to 9.46 x 1012 km.
15. The radius of Jupiter is 11 times the radius of the Earth. Calculate the ratio of the volumes of Jupiter and the Earth. How many Earths can Jupiter accommodate?
Ans.- Let us consider Jupiter and Earth are two spheres with radii R and R’ respectively. Given in the question that radius of Jupiter is 11 times the radius of the Earth.
So, R’= 11R
Volume of sphere of radius r is given as = 4⁄3Ï€r3
Volume of Earth = 4⁄3Ï€r3
And, volume of Jupiter = π(R1)3
=4⁄3 Ï€(R1)3=1331[4/3Ï€R3]
The ratio of the volume of Jupiter and earth
=volume of Jupiter volume of Earth =1331(4/3Ï€R3)4/3Ï€R3=1331
Therefore, this ratio suggests that Jupiter can fit 1331 number of Earth in it.
16. Boojho made the following sketch (Fig. 17.29) of the solar system. Is the sketch correct? If not, correct it.
Ans.- No, the diagram made by the Boojho is not correct, because in the solar system the sequence of the planets of their distance from the sun is like; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Here he had changed the positions of the planets Venus, Mars, Neptune and Uranus. Besides this, he had shown in the diagram that shows the Asteroids belt in the gap between the orbits of Saturn and Jupiter. This is incorrect. The Asteroids belt is located in the middle of the orbits of Jupiter and Mars. The correct diagram of the solar system is given below-
Junior Science Topic - Stars And The Solar System. Chapter notes, video lectures, power point presentation and NCERT exercise solution. (Class 8, CBSE syllabus, chapter 17)
By - EduPorm India - The Educational Platform
.png)
){kind=link}