EE8086 NANYANG TECHNOLOGICAL UNIVERSITY SEMESTER 2 EXAMINATION 2007-2008 EE8086 – Astronomy: Stars, Galaxies and Cosmology April / May 2008 Time Allowed: 2 hours INSTRUCTIONS 1. This paper consists of 50 multiple choice questions only and comprises ELEVEN (11) pages. Each multiple choice question carrying 2 marks. Answer ALL the multiple choice questions. Indicate your answer to the multiple choice questions on the Answer Sheet provided by shading the appropriate circle for each question. 2. 3. 1. Which of the following statements does not use the term light-year in an appropriate way? A. B. C. D. E. A light-year is about 10 trillion kilometers. It's about 4 light-years from here to Alpha Centauri. The Milky Way Galaxy is about 100,000 light-years in diameter. It will take the Voyager spacecraft about 20,000 years to travel just 1 lightyear. It will take me light-years to complete this examination. 2. How are galaxies important to our existence? A. Without galaxies, the universe could not be expanding. B. Without galaxies, there could not have been a Big Bang. C. Galaxies recycle heavy elements produced in stars into future generations of stars. D. Galaxies prevent planets from leaving their orbits around stars; e.g., our galaxy prevents the earth from leaving its orbit of the Sun. E. Galaxies provide the gravity that prevents us from falling off the earth. 1 EE8086 3. Why is it summer in the Northern Hemisphere when it is winter in the Southern Hemisphere? A. The Northern Hemisphere is tilted away from the Sun and receives more indirect sunlight. B. The Northern Hemisphere is "on top" of the earth and therefore receives more sunlight. C. The Northern Hemisphere is closer to the Sun than the Southern Hemisphere. D. The Northern Hemisphere is tilted toward the Sun and receives more direct sunlight. E. It is not: both hemispheres have the same seasons at the same time. 4. Which of the following statements about the Moon is true? A. The Moon goes through a cycle of phases because it always has the same side facing the earth. B. If you see a full Moon from North America, someone in South America would see a new moon. C. The side of the Moon facing away from the earth is in perpetual darkness. D. The Moon is visible only at night. E. The Moon's distance from the earth varies during its orbit. 5. Which of the following statements is not true? A. Atmosphere of Venus is very similar to that of Earth. B. The mass of Jupiter can be calculated by measuring the orbital period and distance of one of Jupiter’s moons. C. The corona and chromosphere are hotter than the photosphere. D. Galaxy collisions were more common in the past. E. Some galaxy clusters are still growing today. 6. Which of the following never goes in retrograde motion? A. B. C. D. E. Mars the Sun Jupiter Saturn Venus 7. Why were ancient peoples unable to detect stellar parallax? A. B. C. D. E. They did detect it, but they rejected the observations. They did not observe for long enough periods of time. They could not see distant stars. They did not have the ability to measure very small angles. They did not look for it. 2 EE8086 8. Which of the following statements about scientific models is true? A. B. C. D. E. All models that explain nature well are correct. A model tries to represent all aspects of nature. A model tries to represent only one aspect of nature. A model can be used to explain and predict real phenomena. All current models are correct. 9. How did the Ptolemaic model explain the apparent retrograde motion of the planets? A. It held that the planets moved along small circles that moved on larger circles around the earth. B. It placed the Sun at the center so that the planets' apparent retrograde motion was seen as the earth passed each one in its orbit. C. It held that sometimes the planets moved backward along their circular orbits. D. It held that the planets moved along small circles that moved on larger circles around the Sun. E. It varied the motion of the celestial sphere so that it sometimes moved backward. 10. Who discovered that Jupiter has moons? A. B. C. D. E. Aristotle Ptolemy Kepler Galileo Tycho Brahe 11. Which of the following statements is true? A. Green is green in colour because it absorbs green light but reflects all other colours. B. Stars are continually forming in the halo of our Galaxy today. C. Although antimatter is an interesting theoretical idea, there is no evidence that it actually exists. D. X-ray, which has more energy, travels faster through space than visible light. E. The upper limit to the mass of a white dwarf is 1.4 solar masses. 3 EE8086 12. From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star has the same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude? A. B. C. D. E. The star is getting hotter. The star is moving toward us. The "star" actually is a planet. The star is getting colder. The star is moving away from us. 13. Which of the following is not an exception to the general patterns of motion in the solar system? A. B. C. D. E. The counterclockwise rotation of Venus. The retrograde rotation of Triton around Neptune. The rings of Saturn. The extreme axis tilt of Uranus. The large size of the earth's moon. 14. Which planet has the highest average surface temperature, and why? A. B. C. D. E. Mercury, because it is closest to the Sun. Jupiter, because it is so big. Mercury, because of its dense carbon dioxide atmosphere. Venus, because of its dense carbon dioxide atmosphere. Mars, because of its red color. 15. Which two properties are most important in determining the surface temperature of a planet? A. B. C. D. E. Internal temperature and atmosphere. Size and chemical composition. Size and distance from the Sun. Distance from the Sun and atmosphere. Size and atmosphere. 16. How is the atmosphere of a planet affected by the rotation rate? A. The rotation rate determines how long the planet is able to retain its atmosphere. B. Faster rotation rates raise the atmospheric temperature. C. Faster rotation rates raise surface temperatures and thus determine how much material is gaseous versus icy or liquid. D. The rotation rate determines how much atmosphere a planet has. E. Faster rotation rates produce stronger winds. 4 EE8086 17. Which of the following statements is true? A. The Big Bang predicts that one in four atoms in the universe is helium. B. Accretion and radioactivity are the two internal energy sources produce heat by converting gravitation potential energy into thermal energy. C. According to the theory of solar system formation, the original solar nebula happened to be disk-shaped by chance. D. The spiral arms of a spiral galaxy are bright because they contain more hot young stars than other parts of the disk. E. The elements heavier than hydrogen and helium come from the Big Bang. 18. Suppose you put two protons near each other. Because of the electromagnetic force, the two protons will A. B. C. D. E. repel each other. attract each other. turn into pure energy. remain stationary. join together to form a nucleus. 19. Which of the following statements about the sunspot cycle is not true? A. With each subsequent peak in the number of sunspots, the magnetic polarity of the Sun is the reverse of the previous peak. B. The number of solar flares peaks about every 11 years. C. The rate of nuclear fusion in the Sun peaks about every 11 years. D. The cycle is truly a cycle of magnetic activity, and variations in the number of sunspots are only one manifestation of the cycle. E. The number of sunspots peaks approximately every 11 years. 20. What two physical processes balance each other to create the condition known as gravitational equilibrium in stars? A. B. C. D. E. the strong force and the weak force the gravitational force and outward pressure the strong force and the electromagnetic force the gravitational force and surface tension the gravitational force and the weak force 21. On a Hertzsprung-Russell diagram, where on the main sequence would we find stars that have the greatest mass? A. B. C. D. E. lower right upper right upper left lower left none of the above 5 EE8086 22. Which of the following statements is true? A. There are no auroras on Venus because it lacks atmospheric oxygen. B. There is no gravity in space. C. No visible light can escape a black hole, but gamma rays, X-rays and neutrinos can. D. The habitable zone around a star refers to the places where living organisms are found. E. Based on all we know about the terrestrial worlds, its size is the single factor appears to play the most important role in a terrestrial planet’s geological destiny. 23. Which of the following statements about an open cluster is true? A. B. C. D. E. All stars in the cluster are approximately the same colour. All stars in the cluster have approximately the same mass. All stars in the cluster are approximately the same age. There is an approximately equal number of all types of stars in the cluster. All stars in the cluster will evolve similarly. 24. Our Sun is a star of spectral type A. B. C. D. E. S G F M Z 25. Sirius is a spectral type A star whereas Rigel is a spectral type B star. What can we conclude? A. B. C. D. E. Rigel and Sirius have the same core temperature. Sirius has a higher core temperature than Rigel. Sirius and Rigel have the same surface temperature. Sirius has a higher surface temperature than Rigel. Rigel has a higher surface temperature than Sirius. 26. Which of the following statements about brown dwarfs is not true? A. All brown dwarfs have masses less than that about 8% of the solar mass. B. Brown dwarfs form like ordinary stars but their masses are too small to sustain nuclear fusion in their cores. C. Brown dwarfs are supported by degeneracy pressure, which does not depend on the object's temperature. D. Brown dwarfs will eventually collapse to become white dwarfs. E. Brown dwarfs and Jupiter are of similar sizes. 6 EE8086 27. Which of the following statements is true? A. B. C. D. All stars that become supernovae will leave behind a neutron star. One of the four Galilean moons Europa around Jupiter is made of rock. We can see most of the galaxy with visible light. Neptune is denser than Saturn because it has a different composition than Saturn, including a higher proportion of hydrogen compounds and rocks. E. Over the course of the year, all 88 constellations will at some point be visible in the evening sky. 28. What do we call the bright, sphere-shaped region of stars that lie within a few thousand light-years of the center of the Milky Way Galaxy? A. B. C. D. E. the galaxy's disk the galaxy's bulge the galaxy's halo a globular cluster an open cluster 29. What two properties of a Cepheid variable are directly related to one another? A. B. C. D. E. its luminosity and its mass its mass and its distance its shape and its colour the period between its peaks of brightness and its distance the period between its peaks of brightness and its luminosity 30. If we say that a galaxy has a lookback time of 1 billion years, we mean that A. B. C. D. E. its light traveled through space for 1 billion years to reach us. it is 400 million years old. it is 1 billion years old. it was 2 billion light-years away when the light left the galaxy. it is now 1 billion light-years away. 31. Which of the following statements is true? A. The heaviest element produced by stars or in supernovae is silicon. B. Mars appearing red in colour is a result of the scattering of light in the Martian sky. C. Some stars are cool enough to have molecules in their atmosphere. D. The tides on Earth are an example of Newton’s third law of motion. E. All comets orbit the Sun in the same direction as the planets. 7 EE8086 32. What do astronomers mean by the large-scale structure of the universe? A. any individual cluster of galaxies B. any individual galaxy C. the overall arrangement of galaxies, clusters of galaxies, and superclusters in the universe D. the overall shape of the observable universe E. the arrangement of stars in a galaxy 33. Space within clusters of galaxies is not expanding because A. their gravity is strong enough to hold them together even while the universe as a whole expands. B. the universe is not old enough for these objects to have begun their expansion. C. space is expanding within each galaxy in the cluster, which is why clusters tend to grow in size with time. D. expansion of the universe affects only empty space, not space in which matter is present. E. there is not enough matter in the clusters to repel the galaxies away. 34. What happens when a particle of matter meets its corresponding antiparticle of antimatter? A. The question makes no sense, since antimatter does not really exist. B. The combined mass of the two particles is completely transformed into photons. C. They fuse to make a heavier particle. D. They can form a complete atom. E. They merge to form a molecule. 35. Which of the following statements is not true? A. Sunspots are cooler than the surrounding region of the Sun's surface. B. Almost all elements heavier than hydrogen and helium were made inside stars. C. The great contribution of Tycho Brahe was to observe planetary positions with sufficient accuracy so that Kepler could later use the data to discover the laws of planetary motion. D. Asteroids are usually found between the orbits of Mars and Jupiter. E. In our solar system, the jovian planet Jupiter has the largest size. 36. What does cosmological redshift do to light? A. B. C. D. E. slows it down stretches it in wavelength converts all light into infrared makes it brighter makes it dimmer 8 EE8086 37. What does the Schwarzschild radius of a black hole depend on? A. whether the black hole formed in a massive-star supernova or in some other way B. the radius of the black hole, as measured by careful observations of its size C. both the mass and the chemical composition of the black hole D. only the mass of the black hole E. the colour of the black hole 38. Which of the following statements about stars is true? A. B. C. D. E. The apparent brightness of a star depends only on its luminosity. All stars spend approximately the same amount of time on the main sequence. The faster rotating star has wider spectral lines than the slower rotating star. There is no upper limit to the mass of a neutron star. There is no limit to the mass with which a star can be born. 39. Which of the following places is not generally considered a potential home for life in our solar system? A. B. C. D. E. Jupiter's atmosphere Mars Europa Ganymede All of the above 40. When we say that a cluster of galaxies is acting as a gravitational lens, what do we mean? A. B. C. D. E. The overall shape of the cluster is that of a lens. It magnifies the effects of gravity that we see in the cluster. It bends or distorts the light coming from galaxies located behind it. It is an unusually large cluster that has a lot of gravity. The shape of each galaxy in the cluster is that of a lens. 41. Which of the following statements is true? A. The strength of Coriolis effect is dependent only on the rotation rate of a planet. B. Most of the current star formation in the Milky Way occurs in spiral arms. C. Our Sun will likely undergo a nova event in about 5 billion years. D. The gradual disappearing of a crater rim as a result of wind and rain is an example of tectonics. E. Doubling the distance between two objects halves the gravitational force between them. 9 EE8086 42. The main source of energy for a star as it grows in size to become a red giant is A. B. C. D. E. helium fusion in the core. hydrogen fusion in a shell surrounding the central core. hydrogen fusion in the core. gravitational contraction. nuclear fission in the core. 43. Which of the following statements about neutrinos is not true? A. B. C. D. The mass of a neutrino is 20 percent of the mass of an electron. Neutrinos are created as a by-product of the proton-proton chain. About a thousand trillion neutrinos pass through your body every second. Neutrinos have a tendency to pass through just about anything without interactions, making them very difficult to detect. E. Neutrinos have no electrical charge. 44. The faintest star visible to the naked eye has an apparent visual magnitude of about A. B. C. D. E. 0 +6 -6 +1 +10 45. Which of the following best describes rain on Venus? A. It has sulfuric acid rain in its atmosphere, but the drops evaporate before hitting the surface. B. It has liquid water rain that causes erosion on the surface. C. It has sulfuric acid rain that causes erosion on the surface. D. It has liquid water rain in its atmosphere, but the drops evaporate before hitting the surface. E. It does not have rain. 46. Which of the following statements is not true? A. The atmospheric pressure decrease as you go higher in altitude on Earth because gravity gets much weaker with altitude. B. One of the reasons astronomers would like an observatory on the far side of the Moon is the telescope could observe stars even when it is daytime on the Moon. C. The proton-proton chain converts four hydrogen nuclei into one helium nucleus. D. The more distant a star, the smaller its parallax. E. In any star cluster, stars with lower masses greatly outnumber those with higher masses. 10 EE8086 47. We do not expect to find life on planets orbiting high-mass stars because A. B. C. D. E. planets cannot have stable orbits around high-mass stars. their lifetimes are too short. they emit too much ultraviolet radiation. they are too hot to allow for life. they are too cold for life. 48. Which of the following statements correctly describes the law of conservation of energy? A. An object always has the same amount of energy. B. Energy can change between many different forms, such as potential, kinetic, and thermal, but it is ultimately destroyed. C. It is not really possible for an object to gain or lose potential energy, because energy cannot be destroyed. D. The total quantity of energy in the universe never changes. E. The fact that you can fuse hydrogen into helium to produce energy means that helium can be turned into hydrogen to produce energy. 49. Suppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice? A. The clock will fall toward the black hole at a steady rate, so that you will see it plunge through the event horizon within just a few minutes. B. Time on the clock will run faster as it approaches the black hole, and light from the clock will be increasingly blueshifted. C. Time on the clock will run slower as it approaches the black hole, and light from the clock will be increasingly redshifted. D. Time on the clock will run slower as it approaches the black hole, and light from the clock will be increasingly blueshifted. E. The clock will fall faster and faster, reaching the speed of light as it crosses the event horizon. 50. In addition to the conditions required for any solar eclipse, what must also be true in order for you to observe a total solar eclipse? A. B. C. D. E. The Moon's penumbra must touch the area where you are located. The earth must lie completely within the Moon's umbra. The earth must be near aphelion in its orbit of the Sun. The earth must lie completely within the Moon's penumbra. The Moon's umbra must touch the area where you are located. End of Paper 11