Topic outline

    • Stars and Solar System

      Q77. Why does the Sun appear to be bigger and brighter than all other stars?

      Ans. The Sun is the nearest star from us and it is continuously emitting huge amounts of heat and light. Thus, the Sun appear to be bigger and brighter than all other stars.


      Q78. What is an artificial satellite? Name any two artificial satellites launched by India.

      Ans. There are many man-made satellites revolving round the Earth. These are called artificial satellites. Artificial satellites launched by India are INSAT, IRS, Kalpana-1, EDUSAT, etc.

      Q79. Why the planets do not collide while revolving around the Sun?

      Ans. Planets do not collide while revolving around the Sun because each planet has a definite path in which it revolves around the Sun. This path is called an orbit.


      Q80. Which planet is known as evening and morning star and why?

      Ans. Sometimes Venus appears in the eastern sky before sunrise. Sometimes it appears in the western sky just after sunset. Therefore it is often called a morning or an evening star, although it is not a star.


      Q81. Name the eight planets of the Solar System in the order of their increasing distances from the Sun.

      Ans. Our Solar System has eight planets which orbit the sun. In order of distance from the sun they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.


      Q82. What are asteroids? Where are most of them located?

      Ans. There is a large gap in between the orbits of Mars and Jupiter. This gap is occupied by a large number of small objects that revolve around the Sun. These are called asteroids. Asteroids can only be seen through large telescopes.

      Q83. How do the planets stay in orbit around the sun?

      Ans. The Sun and the celestial bodies which revolve around it form the solar system. It consists of large number of bodies such as planets, comets, asteroids and meteors. The gravitational attraction between the Sun and these objects keeps them revolving around it.


      Q84. How long does it take for a full moon to change to new moon?

      Ans. The day on which the whole disc of the moon is visible is known as the full moon day. Thereafter every night the size of the bright part of the moon appears to become thinner and thinner. On the fifteenth day the moon is not visible. This day is known as the new moon day.


      Q85. Why Pluto is not considered as a planet anymore?

      Ans. Till 2006 there were nine planets in the solar system. Pluto was the farthest planet from the Sun. In 2006, the International Astronomical Union (IAU) adopted a new definition of a planet. Pluto does not fit this definition. It is no longer a planet of the solar system.


      Q86. What are outer planets?

      Ans. The planets outside the orbit of Mars, namely Jupiter, Saturn, Uranus and Neptune are much farther off than the inner planets. They are called the outer planets. They have a ring system around them. The outer planets have large number of moons.

      Q87. Why does the Moon shine?
      If the Moon does not have its own light, how are we able to see the moon?

      Ans. The moon does not produce its own light, whereas the Sun and other stars do. We see the moon because the sunlight falling on it gets reflected towards us. We, therefore, see only that part of the moon, from which the light of the Sun is reflected towards us.


      Q88. Do all the stars in the sky move? Explain.

      Ans. No, all the stars in the sky does not move. The earth rotates on its axis from west to east. Therefore, all the stars in the sky seem to move from east to west. 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.


      Q89. What are comets?

      Ans. Comets are also members of our solar system. They revolve around the Sun in highly elliptical orbits. However, their period of revolution round the Sun is usually very long. A Comet appears generally as a bright head with a long tail. The length of the tail grows in size as it approaches the sun. The tail of a comet is always directed away from the sun.


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