INDIAN & WORLD GEOGRAPHY ASTRONOMY 1. What Is the Difference Between Asteroids and Comets?
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INDIAN & WORLD GEOGRAPHY ASTRONOMY 1. What is the difference between asteroids and comets? (2011) 1. Asteroids are small rocky planetoids, while comet are formed of frozen gases held together by rocky and metallic material. 2. Asteroids are found mostly between the orbits of Jupiter and Mars, while comets are found mostly between Venus and Mercury. 3. Comets show a perceptible glowing tail, while asteroids do not. Which of the statements given above is/are correct? (a) 1 and 2 (b) 1 and 3 (c) 3 (d) 1,2 and 3 Ans: B The biggest difference between comets and asteroids is what they are made of. While asteroids consist of metals and rocky material, comets are made up of ice, dust, rocky materials and organic compounds. When comets get closer to the Sun, they lose material with each orbit because some of their ice melts and vaporizes. Asteroids typically remain solid, even when near the Sun. Right now, the majority of asteroids reside in the asteroid belt, a region between the orbits of Mars and Jupiter which may hold millions of space rocks of varying sizes. On the other hand, the majority of comets are in the farthest reaches of our Solar System: either 1. in the Kuiper Belt — a region just outside the orbit of the dwarf planet Pluto that may have millions of icy comets (as well as many icy dwarf planets like Pluto and Eris); or 2. the Oort Cloud, a region where trillions of comets may circle the Sun at huge distances of up to 20 trillion kilometers (13 trillion miles). 2. Which one of the following planets has largest number of natural satellites or moons? (2009) (a) Jupiter (b) Mars (c) Saturn (d) Venus Ans: C . A natural satellite or moon is an astronomical body that orbits a planet or minor planet. In the Solar System there are 178 known natural satellites which orbit within 6 planetary satellite systems. Four IAU-listed dwarf planets are also known to have natural satellites: Pluto, Haumea, Makemake, and Eris. Number of Natural Rank Name Satellites 1 Jupiter 63 2 Saturn 60 3 Uranus 27 4 Neptune 13 5 Pluto 3 6 Mars 2 7 Earth 1 8 Venus 0 9 Mercury 0 3. In order of their distances from the Sun, which of the following planets tie between Mars and Uranus? (2008) (a) Earth and Jupiter (b) Jupiter and Saturn (c) Saturn and Earth (d) Saturn and Neptune Ans: B 4. What is the average distance (approximate) between the Sun and the Earth? (2007) (a) 70xl05km (b) 100xl05km (c) 110xl06km (d) 150xl06km Ans: D The distance from Earth to the sun is called an astronomical unit, or AU, which is used to measure distances throughout the solar system. The AU has been defined as 149,597,870,700 meters (92,955,807 miles). The AU is the average distance from the Earth to the sun. Earth makes a complete revolution around the sun every 365.25 days — one year. However, Earth's orbit is not a perfect circle; it is shaped more like an oval, or an ellipse. Over the course of a year, Earth moves sometimes closer to the sun and sometimes farther away from the sun. Earth's closest approach to the sun, called perihelion, comes in early January and is about 91 million miles (146 million km). The farthest from the sun Earth gets is called aphelion. It comes in early July and is about 94.5 million miles (152 million km). 5. (A): To orbit around the Sun, the planet Mars takes lesser time than the time taken by the Earth. (2006) (R): The diameter of the planet Mars is less than the Earth. (a) Both A and R are true and R is the correct explanation ofA. (b) Both A and R are true but R is not a correct explanation of A. (c) A is true and R is false. (d) A is false and R is true. Ans: D 6. (A): The same face of the Moon is always presented to the Earth. (R): The Moon rotates about its own axis in 23 'A days which is about the same time that it takes to orbit the Earth. (2005) (a) Both A and R are true and R is the correct explanation ofA. (b) Both A and R are true but R is not a correct explanation of A. (c) A is true but R is false. (d) A is false but R is true. Ans: C 7. (A): Existence of human life on Venus is highly improbable. (R): Venus has extremely high level of carbon dioxide in its atmosphere. (2005) (a) Both A and R are true and R is the correct explanation ofA. (b) Both A and R are true but R is not a correct explanation of A. (c) A is true but R is false. (d) A is false but R is true. Ans: A The speculation of life currently existing on Venus decreased significantly since the early 1960s, when spacecraft began studying Venus and it became clear that the conditions on Venus are extreme compared to those on Earth. The fact that Venus is located closer to the Sun than Earth, raising temperatures on the surface to nearly 735 K (462 °C), the atmospheric pressure is 90 times that of Earth, and the extreme impact of the greenhouse effect, make water-based life as we know it unlikely on the surface of the planet. 8. Among the following which planet takes maximum time for one revolution around the Sun? (2003) (a) Earth (b) Jupiter (c) Mars (d) Venus Ans: B 9. Which one of the following statements is correct with reference to our solar system? (2002) (a) The Earth is the densest of all the planets in our solar system (b) The predominant element in the composition of Earth is silicon (c) The Sun contains 75 per cent of the mass of the solar system (d) The diameter of the Sun is 190 times than Earth Ans: B 10. If the stars are seen to rise perpendicular to the horizon by an observer, he is located on the (2001) (a) Equator (b) Tropic of Cancer (c) South Pole (d) North Pole Ans: A Since the stars do not rise or set, you must be at the North (or South) pole of the planet. When you walk to the point where the stars rise and set perpendicular to the horizon, you are at the equator of the planet 11. A 'black hole' is a body in space which does not allow any radiation to come out. This property is due to its (2000) (a) Very small size (b) Very large size (c) Very high density (d) Very low density Ans: C Black holes are stars which have contracted so much that they have developed super density. They are so compact that their gravitational pull is very strong ,that even light of radiatons produced by them cannot escape them.So they cannot be seen by optical telescopes.A black hole is the smallest and densest object in the universe.Nothing that gets into it can ever escape.It can neither crack nor split or decrease in size.It can only grow and nothing in universe can stop it from growing. 12. At which one of the following positions shown in the diagram will the height of the ocean tide be maximum? (1999) (a) M1 (b) M2 (c) M3 (d) M4 Ans: D 13. One Astronomical unit is the average distance between (1998) (a) Earth and the Sun (b) Earth and the Moon (c) Jupiter and the Sun (d) Pluto and the Sun Ans: A The distance from Earth to the sun is called an astronomical unit, or AU, which is used to measure distances throughout the solar system. The AU has been defined as 149,597,870,700 meters (92,955,807 miles). The AU is the average distance from the Earth to the sun. Earth makes a complete revolution around the sun every 365.25 days — one year. 14. Consider the following statements regarding asteroids: (1998) 1. Asteroids are rocky debris of varying sizes orbiting the Sun. 2. Most of the asteroids are small but some have diameter as large as 1000 km. 3. The orbit of asteroids lies between the orbits of Jupiter and Saturn. Of these statements (a) 1,2 and 3 are correct (b) 2 and 3 are correct (c) 1 and 2 are correct (d) 1 and 3 are correct Ans: C Asteroids are small, airless rocky worlds revolving around the sun that are too small to be called planets. They are also known as planetoids or minor planets. In total, the mass of all the asteroids is less than that of Earth's moon. But despite their size, asteroids can be dangerous. Many have hit Earth in the past, and more will crash into our planet in the future. That's one reason scientists study asteroids and are eager to learn more about their numbers, orbits and physical characteristics. If an asteroid is headed our way, we want to know that. Most asteroids lie in a vast ring between the orbits of Mars and Jupiter. This main asteroid belt holds more than 200 asteroids larger than 60 miles (100 kilometers) in diameter. Scientists estimate the asteroid belt also contains more than 750,000 asteroids larger than three-fifths of a mile (1 km) in diameter and millions of smaller ones. Not everything in the main belt is an asteroid — for instance, comets have recently been discovered there, and Ceres, once thought of only as an asteroid, is now also considered a dwarf planet.