September 20, 1999 Dr Michael Burton GENS4001 Astronomy Session 2 Test 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 ON THE FORM Mark the appropriate box from A to D for each question. YOU HAVE 1 HOUR _____________________________________________ 1. In which layer of the Earth's atmosphere does all of the weather occur? a. the troposphere b. the thermosphere c. the stratosphere d. the mesosphere 2. What is the cause of great mountain ranges on the Earth, such as the Rocky Mountains and the Andes? a. A collision of two tectonic plates, where one is folded into mountains while the other is thrust underneath. b. Two tectonic plates being pushed apart by molten rock that is being forced up between them. c. Heat from the Earth's interior causing the Earth's crust to expand and then crumple. d. The carving of continents during ice ages, with the mountains left behind as "islands" in a sea of glaciers. 3. Of what material is the core of the Earth composed? a. Mostly iron. b. Rock of similar composition to that in the crust, but much denser. c. Roughly half rock and half iron. d. Titanium and nickel. 4. Mercury can only be seen easily from Earth a. at midnight, when it is high in the sky. b. near to the Sun, just after sunset or just before sunrise. c. in the winter, when the ecliptic plane is high in the sky at night. d. during a lunar eclipse, when the sky is sufficiently dark near to the Moon, since Mercury is always close to the Moon in our sky. 5. Which of the following features were NOT found on Mars when spacecraft finally visited the planet? a. Deep, winding canyons b. Craters c. Straight canals d. Extinct volcanoes 6. The overall geography of Mars can be best summarized as a. major volcanoes in the northern hemisphere, extensively cratered plains in the southern hemisphere, separated by one major valley system. b. mostly rolling plains, with several volcanoes on top of two continent-sized uplands. c. moving lithospheric plates whose motions have produced long folded mountain chains, deep subduction trenches, and several large rift valleys. d. smooth plains where continuous resurfacing by ongoing volcanic activity has hidden older impact craters and other details. 7. What are the characteristic features on the visible surface of Jupiter? a. Light and dark bands of clouds parallel to the equator. b. Large volcanoes and a long, deep rift valley. c. A greenish, almost featureless cloud layer. d. A bluish tint with high, white clouds and dark storms. 8. The rotation periods for the Jovian planets Jupiter, Saturn, Uranus, and Neptune are a. somewhat shorter than Earth's, about 10 to 20 hours. b. very long, on the order of years, because of the sizes of these planets. c. reasonably long, on the order of several Earth days. d. much shorter than Earth's, between 1 and 2 hours. 9. What were the results of the impacts of the fragments of Comet Shoemaker-Levy 9 into Jupiter? a. Fireballs hotter than the Sun and dark splotches that lasted for months. b. Essentially no visible effects, since the fragments plummeted deep below the cloud layers before being destroyed. c. Holes punched through the clouds and craters gouged into Jupiter's surface. d. Rings of debris flung into orbit around Jupiter's equator. 10. What physical mechanism most probably caused the very long cracks and streaks that crisscross the surface of Europa, the moon of Jupiter? a. Volcanic eruptions caused lava flows that then froze in place. b. They are frozen rivers that, in warmer times, were flowing across the moon's surface. c. Tidal flexing by Jupiter cracked the surface, and subsurface fluids gushed upwards and froze. d. They are the tops of gigantic greenhouses built by inhabitants of Europa to protect their cucumber crops. 11. How would a typical asteroid appear on a time exposure photograph of the sky as it orbited the Sun, if the camera were tracking the background stars? a. It would produce a flash of light as it crossed the field of view of the camera. b. It would produce a short trail as it moved slowly against the background stars. c. It would look like any other star, a small extra dot not shown on star charts of this area of the sky. d. It would look like a small, diffuse patch against the sharp images of stars because of the dust and gas surrounding it. 12. The major difference between the orbital paths of comets and those of the asteroids in the asteroid belt is that a. comet orbits are mostly circular and in the ecliptic plane, whereas the asteroids have elliptical orbits inclined at random to the ecliptic plane. b. cometary orbits are highly elliptical and at random inclinations to the ecliptic plane compared to the circular orbits of asteroids in the ecliptic plane. c. comets never approach closer to the Sun than approximately Jupiter's orbit, whereas some asteroids approach very close to the Sun. d. asteroids orbit the Sun continuously whereas all comets approach the Sun's vicinity only once before leaving the solar system. 13. A typical granule on the surface of the Sun a. arches quietly for several days over a sunspot group. b. is about 30,000 km across and lasts for several hours. c. is a few thousand kilometers across and lasts for about two solar rotations. d. is about 1,000 km across and lasts for a few minutes. 14. Spicules on the solar surface are a. jets of gas surging out of the photosphere of the Sun into the chromosphere, usually at supergranule boundaries. b. curtainlike structures hanging over sunspot regions. c. intense eruptions from sunspot groups and active regions, associated with solar flares. d. streams of solar coronal material, usually seen only during a total solar eclipse. 15. One particular feature of the solar corona is a. its variation with time over periods of a few minutes. b. its very cold temperature. c. its very uniform density and structure. d. its very high temperature. 16. Which of the following letters representing spectral classification signifies the hotter stellar surface temperature? a. K b. B c. G d. A 17. Compared to a star in the middle of the Hertzsprung-Russell diagram, a star in the upper right part of the diagram is a. non-existent, since there are no stars that appear in the upper right part of the diagram. b. larger. c. fainter. d. hotter. 18. Where on the Hertzsprung-Russell diagram do most local stars in our Universe congregate? a. On the main sequence, where stars are generating energy by fusion reactions. b. In the white dwarf area, the "graveyard" of stars. c. In the giants area, where most stars spend the longest time of their lives. d. In the supergiant area, where the most massive stars spend a significant time. 19. Where are the most massive stars to be found in the main sequence of a Hertzsprung-Russell diagram? a. The lower, right end. b. In the center section near to the Sun's position, with lower mass stars on either side. c. The upper, left end. d. Main sequence stars all have approximately the same mass, by definition. 20. Absorption lines in the spectra of binary stars are often seen to change periodically from single to double lines and back again. Why is this? a. Motion toward and away from Earth during their orbital motion at times results in Doppler shift of light from these stars and no shift when the stars are moving perpendicular to the line of sight. b. Oscillations on the surfaces of the stars leads to Doppler-shifted lines. c. The effect of the gravitational field of one star on the atoms of the second star produces spectral line shifts periodically. d. The magnetic field of one star produces Zeeman splitting of spectral lines in atoms of the second star, periodically. 21. Which is the most abundant element in the universe? a. hydrogen b. helium c. oxygen d. carbon 22. What happens to a star after the start of helium nuclear reactions in it core, compared to what it was like before these reactions began? a. The star is smaller and hotter. b. The star is smaller and cooler. c. The star is larger and hotter. d. The star is larger and cooler. 23. How do the stars in a star cluster change with time? a. The highest-mass stars evolve the most quickly. b. The lowest-mass stars evolve the most quickly. c. All stars in it evolve at the same rate. d. The stars with the greatest heavy-element content evolve the most quickly. 24. For an astronomer, what is the significance of the turn-off point in the Hertzsprung-Russell diagram of a star cluster? a. It tells the astronomer the age of the star cluster. b. It tells the astronomer the metal content of the star cluster. c. It tells the astronomer which stars might be about to explode as supernovae. d. It tells the astronomer which stars pulsate in brightness (variable stars). 25. What is the most important use of Cepheid variables for astronomers? a. The distance to a Cepheid variable can be found very easily. b. The metal content of a Cepheid variable can be found very easily. c. The characteristics of the pulsation of a Cepheid variable can be used to investigate conditions in the core of the star. d. The diameter of a Cepheid variable can be found very easily. 26. Planetary nebulae are so-named because a. their spectra appear to be similar to the spectrum of the giant gas planets in our own solar system. b. they rotate slowly and condense into planetary objects around the remaining central star. 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. 27. A white dwarf is a. a hot, main sequence star. b. a type of small protostar. c. a small, very hot, low-mass star. d. an object like Jupiter that was not quite massive enough to become a star. 28. Which nuclear fusion cycle follows the helium fusion phase as a massive star evolves? a. silicon "burning" b. oxygen "burning" c. carbon "burning" d. iron "burning" 29. Pulsars, emitting very regular radio, and sometimes visible light pulses, are what type of object? a. Rapidly rotating binary star systems in which the stars undergo regular eclipses as seen from Earth. b. Pulsating variable stars. c. Rapidly rotating neutron stars. d. Black holes, with material falling into them regularly. 30. Which is the correct sequence for the following end-points of stellar evolution, in order of increasing mass? a. white dwarf, black hole, neutron star b. black hole, neutron star, white dwarf c. white dwarf, neutron star, black hole d. neutron star, black hole, white dwarf 31. Interstellar dust obscures our view of distant regions of space at optical wavelengths. In this regard, which of the following statements is true? a. The regions are severely obscured only in the plane of the Galaxy. b. The regions are obscured the least in the plane of the Galaxy, and are strongest when we look out into the galactic halo, at right angles to this plane. c. The regions are obscured roughly uniformly over the whole sky. d. The obscured regions are very clumpy and random over the whole sky, the individual absorbing dust clouds showing no preference for one particular direction or plane. 32. When distances were carefully measured from Earth to globular clusters above and below the Milky Way plane, (where our view of them is not obscured by interstellar dust and gas) their distribution was found to be a. concentrated in the plane of the Milky Way and clustered around the Sun's position, indicating that the Sun is close to the galaxy's center. b. uniformly distributed throughout space, with no concentration in any area of the Milky Way. c. spherically symmetric about a point in the constellation Sagittarius and concentrated in that direction. d. in a relatively flat disk almost perpendicular to the plane of the galaxy, with relatively higher density of clusters towards its center. 33. Where in space would you look for a globular cluster? a. In the asteroid belt. b. In the Milky Way disk, moving in a circular orbit around the galactic center. c. Only in elliptical galaxies, since they are composed of old stars and do not exist in young systems like spiral galaxies. d. In the Milky Way galactic halo, orbiting the galactic center in a long elliptical orbit around the galactic center. 34. The Milky Way in which the Sun resides is an example of which type of galaxy? a. An elliptical galaxy. b. An irregular galaxy. c. A normal spiral galaxy. d. It is not a galaxy at all, but a large cluster of stars. 35. When we measure the narrow line emissions of hydrogen at 21-cm radio wavelengths along a particular line of sight through the disk of our Galaxy, we can tell the distances to different hydrogen clouds because a. the emission is weaker from clouds that are further away. b. clouds that are further away have smaller angular sizes. c. clouds at different distances have different Doppler shifts because of the rotation of the Galaxy. d. absorption of extragalactic radiation at this wavelength will be greater, the further away the absorber is from the Sun. 36. The typical diameter of a spiral galaxy is about a. 1 light-year. b. 100 light-years. c. 107 light-years. d. 105 light-years. 37. Why should spiral arms not exist in galaxies? a. Differential rotation should wind the arms up until they disappear. b. There is no known mechanism to generate spiral arms. c. Spiral arms require new stars, and previous new stars should have already used up all of the interstellar medium; no new stars should be forming now. d. Galaxies are not rotating fast enough to support spiral arms. 38. How many stars per cubic parsec are there in the spiral arms of a spiral galaxy, compared to the regions between the spiral arms? a. There are about 5% more in the spiral arms than in the regions between the arms. b. There are a lot of stars in the spiral arms and none at all in the regions between the arms. c. There are about twice as many stars in the spiral arms than in the regions between the arms. d. There are more than 100 times as many stars in the spiral arms as in the regions between the arms. 39. What is a barred spiral galaxy? a. A galaxy with a bar through the nuclear bulge, and the spiral arms starting from the ends of the bar. b. A galaxy with a bar extending across an entire diameter and the arms starting at various positions along the bar. c. A galaxy in which the arms form straight bars instead of curved lines. d. A spiral galaxy with a straight bar instead of a nuclear bulge. 40. How do spiral galaxies rotate? a. The arms trail the rotation (point back). b. The arms lead the rotation (point forwards). c. They don't rotate; if they did the spiral pattern would soon disappear. d. We don't know; they rotate too slowly for us to have seen any motion in the time since galaxies were discovered. 41. What is an elliptical galaxy? a. A galaxy with an elliptical outline and a smooth distribution of brightness (no spiral arms). b. A spiral galaxy seen from an angle, giving it an elliptical profile. c. Any galaxy with an elliptical halo when observed at radio wavelengths. d. A spiral galaxy with an elliptically-shaped nuclear bulge and the spiral arms starting from the ends of the ellipse. 42. In which of the following types of galaxy is star formation no longer occurring? a. spiral galaxies b. elliptical galaxies c. irregular galaxies d. barred spiral galaxies 43. Which are the largest galaxies in the universe? a. giant elliptical galaxies b. large spiral galaxies like the Milky Way Galaxy c. irregular galaxies d. lenticular galaxies 44. The Magellanic clouds seen from the southern hemisphere are examples of what type of objects? a. irregular galaxies b. spiral galaxies c. planetary nebulae d. supernova remnants 45. "Standard candles," which are important for finding distances to remote galaxies, are a. standard laboratory light sources with which the brightness of a galaxy can be compared. b. standard bars of known length with which the size of a galaxy can be measured. c. heat sources used for calibrating infra-red observations of galaxies. d. stars and other objects of known intrinsic brightness. _____________________________________________