Dr Michael Burton GENS4001 Astronomy Session 1 Test 1999 Name: _______________________ Instructions: Read each question carefully before answering. Write your name, initials and student number in the appropriate boxes. WRITE YOUR TEST NUMBER IN THE OTHER DATA BOXES Mark the appropriate box from A to D for each question. YOU HAVE 1 HOUR _____________________________________________ 1. Which of the planets fits the following description: "Cool, solid surface with an atmosphere of N2 and O2, and H2O clouds"? a. Mercury b. Mars c. Earth d. Venus 2. Which of the following mechanisms is most likely to have taken place while the Earth was molten, to form the present structure of the Earth? a. Heavy elements sank to the center under gravity while lighter materials rose to the surface and solidified into rocks. b. Lighter elements sank to the center leaving the heavier material to form the rocky surface after cooling. c. Hydrogen and helium became highly compressed by gravity and sank to the core below a layer of heavier rocky material. d. All materials were thoroughly mixed by convection in the molten state, and the Earth remained mixed as it cooled. 3. What appears to be the "impact history" of cratering on the Moon? a. Short periods of heavy bombardment alternating with long periods of light bombardment throughout the Moon's life. b. An early period of heavy bombardment, then very light bombardment to the present. c. More-or-less constant bombardment from the earliest times to the present. d. Heaviest bombardment when the Moon first formed, gradually decreasing to light bombardment today. 4. If astronauts were to set up a permanent settlement at Tranquility Base on the Moon, how many times each year would the Earth rise and set as seen by a resident of this base? a. 13 times each year. b. Once each year. c. 12 times each year. d. Never - the Earth would remain essentially motionless in the sky. 5. The water on the side of the Earth that faces away from the Moon a. experiences no tidal force. b. experiences either a high tide or a low tide, depending on the angle to the Sun. c. experiences a high tide because the Moon in effect pulls the solid Earth out from under the water on the far side. d. experiences a low tide because all of the Earth's water is pulled towards the side of the Earth that faces the Moon. 6. At opposition, when Mars comes relatively close to Earth, where would it be seen in the sky by an observer in the Earth's northern hemisphere? a. high in the south at midnight b. high in the south at sunset c. on the western horizon at midnight d. high in the north at midnight 7. The major volcanoes on Mars have formed a. in mountain belts where the planet's surface is being stressed as it is bent and subducted back into the mantle. b. on long, interconnected ridges where magma, rising from the mantle, is pushing the crust apart. c. where shrinkage of the crust during cooling early in the planet's history has wrinkled the surface. d. over individual stationary "hot-spots" in the underlying molten mantle. 8. Which of the following statements is true for Mars? a. Water can be seen in the bottoms of river valleys on spacecraft photographs. b. There are linear canals, apparently built to carry water for irrigation, which criss-cross the planet. c. Mars has dry riverbeds but no liquid water on its surface at the present time. d. There is no evidence of there ever having been water on Mars. 9. Scientists have now examined rocks that came from Mars in their laboratories on Earth because a. a large impact that occurred on the Martian surface early in its history created a vast dust cloud through which Earth passes once per year and samples of this dust have now been collected by the Space Shuttle. b. several meteorites found in Antarctica are now thought to have been knocked off Mars and fallen to Earth. c. spacecraft have been to the surface of Mars and have returned with samples of Martian rocks and soil. d. an orbiting spacecraft scooped up Martian dust during its passage by Mars and then returned to Earth. 10. Which object or group of objects below rotates the most quickly around their own axes? a. The terrestrial planets. b. The Jovian planets. c. The Sun. d. The Earth's Moon. 11. What is the Great Red Spot on Jupiter? a. The point where charged particles from the satellite Io collide with Jupiter's cloud tops. b. A region over the South Pole of Jupiter where ammonia compounds have condensed in the colder atmosphere. c. A large, long-lived, anticyclonic storm that is maintained by the circulation in Jupiter's atmosphere. d. The summit of a large mountain that rises above the upper cloud level. 12. What effect did Comet Shoemaker-Levy 9 have on the atmosphere of Jupiter? a. It had no lasting effect beyond the initial burst of hot gas. b. It created dark patches that lasted for months. c. It created white clouds of ammonia and water ice crystals that lasted for several days. d. It disrupted the atmospheric circulation of light and dark zones for almost a month. 13. One of the most important sources of heat in the interiors of moons that orbit close to giant planets is a. continuous tidal distortion from the planet and other moons. b. reflection of sunlight from the planet's surface. c. decay of radioactive elements within the moons. d. re-radiation of thermal energy received from the planet. 14. An asteroid is a. a meteorite before it enters the atmosphere and plunges to Earth. b. another name for the nucleus of a comet, a volatile object that moves around the Sun in a long, elliptical orbit. c. a small, easily recognizable group of stars within a constellation. d. a small planetary object moving in an orbit around the Sun. 15. Most comet nuclei are believed to be a. carbonaceous chondrite meteorites, carbon material, ignited by sunlight and trailing long smoke trails. b. pieces of rock or iron chipped from asteroids by impacts. c. pieces of dusty ice, left over from the formation of the solar system. d. pieces of dirty ice, ejected from the surface of the icy satellites of the outer planets by asteroid impacts. 16. What is the photosphere of the Sun? a. The middle layer of the Sun's atmosphere. b. The region of convecting gases below the visible surface of the Sun. c. The visible "surface" of the Sun. d. The core of the Sun, where nuclear energy is generated. 17. The 11 year sunspot cycle on the Sun is a. an extremely regular build-up and decay of the number of sunspots, with a precise period of 11.3 years. b. a somewhat irregular but always present cycle of build-up and decay of sunspot numbers. c. the regular movement of a relatively constant number of sunspots from the poles to the equator of the Sun over an 11-year period. d. an irregular cycle averaging about 11 years, but sometimes disappearing entirely. 18. What is the energy source for the Sun? a. Heat released by gravitational contraction. b. Primordial heat left over from when the Sun first formed. c. Radioactivity. d. Thermonuclear fusion in the core. 19. Approximately where is the Sun in terms of its total lifetime? a. It is about 3/4 of the way through its life. b. It is about 1/10 of the way through its life. c. It is about 1/4 of the way through its life. d. It is about half way through its life. 20. Which is the most abundant element in the universe? a. helium b. hydrogen c. oxygen d. carbon 21. New stars are formed from a. free space out of pure energy. b. supernova remnants. c. activity in the centers of galaxies. d. huge, cool dust and gas clouds. 22. What is a protostar? a. A star near the end of its life, before it explodes as a supernova. b. A small interstellar cloud, before it collapses to become a star. c. A shell of gas left behind from the explosion of a star as a supernova. d. A sphere of gas after collapse from an interstellar cloud but before nuclear reactions have begun. 23. Main sequence stars do not have masses larger than about 100 solar masses. The reason that stars of larger mass do not exist is that a. the thermonuclear reactions in such stars proceed so rapidly that the star explodes. b. interstellar clouds of greater mass break up to become binary or multiple star systems, not single stars. c. their temperature becomes so high that they are disrupted by the pressure of radiation inside them. d. such stars contract directly to become planetlike objects. T, Page 254 24. How is the length of a star's lifetime related to the mass of the star? a. Lower-mass stars run through their lives faster and have shorter lifetimes. b. A star's lifetime does not depend on its mass. c. The lifetimes of stars are too long to measure, so it is not known how (or if) their lifetimes depend on mass. d. Higher-mass stars run through their lives faster and have shorter lifetimes. 25. What is a red giant? a. A star that is burning hydrogen into helium in a shell around the core. b. A protostar in the "upper right" part of the Hertzsprung-Russell diagram. c. A large emission nebula. d. A large, red star that is burning hydrogen into helium in its core. 26. How large will the Sun be as a red giant? a. about 1/10 AU radius (1/4 of Mercury's orbit) b. about 1/2 AU radius (beyond Mercury's orbit) c. about 1.5 AU radius (out to Mars' orbit) d. about 1 AU radius (out to the Earth's orbit) 27. Which of the following objects is NOT an end-point of a star's evolutionary life? a. neutron star b. black hole c. red giant d. supernova 28. Planetary nebulae are so-named because a. they rotate slowly and condense into planetary objects around the remaining central star. b. their spectra appear to be similar to the spectrum of the giant gas planets in our own solar system. c. these extended objects, often green-colored, looked like planets to Herschel when he first observed them in the 1700s through his telescopes. d. the ejected material is rich in carbon and oxygen, necessary elements for the manufacture of planets in the nebulae surrounding stars. 29. The energy generation process inside a white dwarf star is a. hydrogen fusion. b. the combining of protons and electrons to form neutrons within its core. c. the helium flash; very efficient and rapid helium fusion. d. non-existent; a white dwarf star is simply cooling by radiating its original heat. 30. A pulsar is a. a pulsating star, in which size, temperature, and light intensity vary regularly. b. a rapidly rotating neutron star, emitting beams of radio, and sometimes x-ray and visible, energy. c. an object at the center of each galaxy, supplying energy from its rapid rotation. d. a binary star in which matter from one star is falling onto the second star. 31. The dimensions of the disk of our Milky Way Galaxy are a. diameter 28,000 light-years; thickness 2,000 light-years. b. diameter 100,000 light-years; thickness, 2,000 light-years. c. diameter 2,000 light-years; thickness, 100,000 light-years. d. diameter 10,000 light-years; thickness, 28,000 light-years. 32. The ratio of thickness to diameter of the Milky Way Galaxy is a. 1/1000. b. 1/5. c. 1/50. d. 1/500. 33. Where is the solar system located in our Galaxy? a. In the galactic nucleus. b. It is not in a galaxy, but in the intergalactic space between galaxies. c. In the galactic halo. d. In the galactic disk. 34. The Milky Way in which the Sun resides is an example of which type of galaxy? a. An irregular galaxy. b. An elliptical galaxy. c. It is not a galaxy at all, but a large cluster of stars. d. A normal spiral galaxy. 35. The time taken for the Sun to orbit the galactic center once in its motion in the Galaxy is a. about a half million years. b. 230 million years. c. 2.3 million years. d. 28,000 years. 36. Which parameter is plotted as a function of distance from the galactic center in a rotation curve of a galaxy? a. The mass of matter inside the distance from the galactic center. b. The speed of stars orbiting the galactic center. c. The thickness of the galactic disk. d. The mass of cool hydrogen gas. 37. The presence of a very large amount of unseen ("dark") matter in the halo of our Galaxy is deduced from a. the unexpected absence of luminous matter (stars, etc.) beyond a certain distance from the galactic center. b. the rotation curve of our Galaxy, in which orbital speeds of stars appear to obey Kepler's Law. c. the high amount of interstellar absorption in certain directions. d. the rotation curve of our Galaxy, in which orbital speeds of stars in the outer regions of the Galaxy are significantly higher than is predicted by Kepler's Law in which the value for the observed mass in the galaxy is used. 38. Quasars all appear to be a. moving across our line of sight at very high speeds, as seen from time-lapse photographs. b. extremely massive objects in our galaxy, their intense surface gravity having red-shifted their spectra. c. moving away from us at very high speeds, at up to 90% of the speed of light. d. moving towards us at high speeds, as high as 90% of the speed of light. 39. In relation to the universe, what does "isotropy" mean? a. The speed of expansion at any given distance is the same at all times. b. The expansion is the same in all directions. c. The speed of expansion is the same at all distances. d. The universe is the same everywhere, neither expanding nor contracting. 40. Why is the universe expanding? a. Because an infinitely-dense clump of matter exploded, sending the galaxies (or superclusters of galaxies) hurtling out through space. b. Because the energy from all the stars is heating the universe, making it expand like a gas that is heated. c. It's not expandingÄÄit is we who are getting smaller, making the universe seem bigger and bigger. d. Because spacetime itself is expanding, carrying the galaxies (or superclusters of galaxies) with it. 41. What is the "cosmological redshift"? a. The stretching of the wavelengths of photons as they travel through expanding space. b. Photons lose energy by interacting with virtual particles in the vacuum, so their wavelength gradually increases as they travel towards us through space. c. The stretching of the wavelengths of photons as they pass through absorbing matter in galaxies between us and the emitting galaxy. d. The stretching of the wavelengths of photons by the Doppler shift, because they are emitted by galaxies that are moving away from us. 42. In cosmology, the constant that is intimately related to the present "age" of the universe is a. G, the universal gravitational constant. b. the Planck time, 10-43 s, in which space and time came into existence. c. the constant in Wien's law of radiation. d. 1/H0, the inverse of the Hubble constant of expansion. 43. Good evidence for an original Big Bang that "created" our universe comes from a. a background "glow" of microwaves, with blackbody temperature of about 3 K. b. the rapid motions of some nearby stars, such as Barnard's Star. c. the measurement of the rotation of our galaxy. d. the amount of gas and dust in the solar neighborhood. 44. The cosmic microwave background radiation is not uniform over the skyÄÄit is slightly hotter towards the constellation Leo and slightly cooler in the opposite direction, towards Aquarius. Why? a. That's the way the universe beganÄÄhotter in one direction and cooler in the other. b. The background radiation really is uniform; the observed difference is due to the Earth's motion through the universe. c. The Earth is slightly off-center in the universe, so one side of the universe is a bit closer and the other is a bit further away. d. The difference is probably a statistical fluctuation, and therefore not real. 45. Galaxies throughout the universe appear to be distributed a. uniformly throughout space. b. in groups and surfaces surrounding vast voids, much like the surfaces of giant bubbles. c. around a single point in space, the presumed location of the original Big Bang which created the universe. d. mostly in a single spherical shell surrounding a void in space, presumed to have been caused by a vast explosion at the time of the Big Bang.