1) A large gas cloud in the interstellar medium that contains several type O and B stars would appear to us as 1) A) a reflection nebula. B) a dark patch against a bright background. C) a dark nebula. D) bright blue. E) an emission nebula. 2) The spectra of interstellar gas clouds show that they have the same basic composition as 2) A) Earth's atmosphere. B) interstellar dust. C) asteroids. D) the Martian polar caps. E) stars. 3) Spectra of stars often show narrow absorption lines from interstellar matter. What type of interstellar matter produces these? 3) A) dust B) molecules C) ionized gas D) neutral gas E) all of the above 4) The relative density of dust to gas is least in which place? 4) A) the interstellar medium B) dark nebulae C) reflection nebulae D) the atmosphere of Earth E) molecular clouds 5) The average temperature of the typical dark dust cloud is about 5) A) 2.73 K. B) 3,000 K. C) 0 K. D) 100 K. E) 6,000 K. 6) The Local Bubble was probably created by: 6) A) a nearby supernova perhaps 300,000 years ago, brighter than the Full Moon. B) the magnetic fields of the Milky Way in our spiral arm. C) the interaction between the solar wind and the Oort Cloud. D) the strong solar winds created by the new-born sun. E) the Crab Nebula supernova of 1054 AD. 7) Which statement about the dark nebulae is true? 7) A) They can be penetrated only with longer wavelengths such as radio and infrared. B) They block the vast majority of radio waves from our Galaxy. C) They can be penetrated only with shorter waves, such as UV and x-ray. D) Hydrogen and helium are the chief absorbing and scattering agents. E) They comprise the majority of the mass of the Galaxy. 8) What feature of interstellar dust is inferred by the polarization of starlight? 8) A) its location in space B) its presence in dark nebulae - 1 -
C) its composition D) its shape E) its presence in molecular clouds 9) Complex molecules in space are found: 9) A) surrounding the more energetic young stars. B) in the photospheres of red giant stars. C) inside dense dust clouds. D) in the coronas of stars like our Sun. E) scattered evenly throughout interstellar space. 10) Some regions along the plane of the Milky Way appear dark because 10) A) many brown dwarfs in those areas absorb light which they turn into heat. B) many black holes absorb all light from those directions. C) there are no stars in these areas. D) stars in that region are hidden by dark dust particles. E) stars in that region are hidden by interstellar gas. 11) Why are dark dust clouds largely misnamed? 11) A) They contain much more gas than dust. B) Dust clouds do radiate energy, but not as much light as the stars do. C) It is ice, not dust, which make them look dark. D) The cloud is an illusion, for the dust is evenly distributed around the Galaxy. E) All of the above are correct. 12) Why is 21-cm radiation so important to the study of interstellar matter and the Galaxy? 12) A) It is emitted only in hot regions of star formation, so the pattern of the spiral arms of the Galaxy can be mapped. B) It helps locate the galactic core in Sagittarius. C) Emitted by hydrogen, it passes through interstellar dust and lets us to map the entire Galaxy. D) It is emitted by most stars, enabling astronomers to map the entire Galaxy. E) Emitted by carbon monoxide, it passes through interstellar gas and lets us to see places rich in organic molecules around the Galaxy. 13) Which statement is true about the interstellar medium? 13) A) Gas obscures the light from distant stars. B) Gas contains a lot of carbon atoms. C) We know more about the gas than the dust. D) Dust is spread uniformly through the galaxy. E) Dust blocks the longest electromagnetic wavelengths. 14) Unlike the ultraviolet photons originally emitted by the embedded stars of an emission nebula, the photons emitted by the recombination of electrons with atoms 14) A) do not escape the nebula. B) escape the nebula. C) bounce around inside the nebula. D) are scattered by the dust particles. E) are re-absorbed by neutral hydrogen atoms. 15) Which of these is NOT a source of the shock waves that lead to protostars? 15) A) radiation from the OB stars in emission nebulae - 2 -
B) expanding Herbig-Haro objects C) violent supernovae explosions D) collisions between galaxies E) expanding planetary nebula shells 16) How long does it take an M class star to reach the main sequence, compared to a solar type star? 16) A) about twice as long B) longer than the age of the Galaxy C) about the same, 30 million years D) about twenty times longer E) a tenth as long 17) From stage 4 to stage 7 of star formation, the object plotted on the H-R diagram moves so that 17) A) its luminosity increases, while its temperature stays the same. B) its luminosity stays the same, and its temperature stays the same. C) its luminosity decreases, while its temperature stays the same. D) its luminosity increases, while its temperature increases. E) its luminosity decreases, while its temperature increases. 18) How are T Tauri stars characterized observationally? 18) A) by very high magnetic fields and large starspots B) by sudden changes in their brightness C) by very rapid rotation D) by very high temperatures E) They are newly-formed stars that are short period binaries. 19) If the initial interstellar cloud in star formation has a mass sufficient to form hundreds of stars, how does a single star form from it? 19) A) A supernova blows the cloud up and dissipates the majority of the gas. B) One star forms and the rest of the matter goes into making planets, moons, and other objects of a solar system. C) The cloud is disrupted by rotation so that it reduces its mass down to that of a typical star. D) One star forms at its center and blows the rest of the matter back into space. E) The cloud fragments into smaller clouds and forms many stars at one time. 20) Which relationship concerning the mass of protostars is false? 20) A) The more massive ones will be the hottest and most luminous. B) The more massive ones will reach the main sequence first. C) The more massive ones create a lot of ultraviolet as well as visible light. D) The more massive ones one will be made of the heaviest elements. E) The more massive ones are so luminous they ionize the gas, hence red H II regions. 21) What happens when an interstellar cloud fragment shrinks? 21) A) Density rises. B) It first becomes opaque. C) Temperature rises. D) Pressure rises. E) all of the above 22) As a star forms, the photosphere first appears: 22) A) when contraction slows down. - 3 -
B) when the star reaches the main sequence. C) when the planetary nebula is expelled. D) when nuclear fires ignite. E) when the protostar forms. 23) What is the key factor that determines the temperature, density, radius, luminosity, and pace of evolution of a protostellar object? 23) A) magnetism of the nebula B) temperature of the nebula C) rotation of the nebula D) mass of the nebula E) composition of the nebula 24) At what stage of evolution do T Tauri stars occur? 24) A) after the star has established itself as a main sequence star B) just as the collapsing cloud becomes luminous C) when a protostar is on the verge of becoming a main sequence star D) just after the planetary nebula is expelled E) just prior to the protostar stage 25) What kind of variable stars are pre-main Sequence stars undergoing gravitational contraction and exhibiting erratic changes in their luminosities? 25) A) Herbig-Haro B) RR Lyrae C) R Coronae Borealis D) Cepheid E) T Tauri 26) Besides mass the other factor that influences where a star appears on the main sequence is 26) A) chemical composition of the cloud. B) the type of cluster the star is formed in. C) distance from Earth. D) number of stars in the cluster. E) the motion of the star. 27) In stage 6 or 7 of the formation of a large cluster of stars, a nebula is formed around the cluster. This happens because 27) A) there are massive O and B stars emitting high energy photons that ionize the remainder of the cloud. B) the number of stars is so great and so intense that the gas from the original cloud is ionized. C) there are thousands of sun-like stars with planets around them and the formation of planets ionizes the leftover gas. D) the stars are out of their coccoons of dust and their radiation ionizes the gas from the original cloud. E) there are brown dwarfs everywhere in between the stars, so the gas is lit up by their low-intensity light. 28) On an H-R diagram, a protostar would be 28) A) below and to the left of the main sequence. B) above and near the upper left of the main sequence. C) on the main sequence at the extreme lower right. D) below and near the right side of the main sequence. - 4 -
E) above and to the right of the main sequence. 29) What are black dwarfs? 29) A) the lowest mass main sequence stars B) pulsars that have slowed down and stopped spinning C) the end result of massive star evolution D) cooled off white dwarfs that no longer glow visibly E) objects that are not quite massive enough to be stars 30) A star (no matter what its mass) spends most of its life: 30) A) as a planetary nebula. B) as a main sequence star. C) as a red giant or supergiant. D) as a protostar. E) as a T Tauri variable star. 31) What spectral type of star that is still around formed most recently? 31) A) M B) F C) K D) O E) A 32) A solar mass star will evolve off the main sequence when 32) A) it completely runs out of hydrogen. B) it builds up a core of inert helium. C) it loses all its neutrinos, so fusion must cease. D) it expels a planetary nebula to cool off and release radiation. E) it explodes as a violent nova. 33) As a 4-10 solar mass star leaves the main sequence on its way to becoming a red supergiant, its luminosity 33) A) increases. B) first increases, then decreases. C) first decreases, then increases. D) decreases. E) remains roughly constant. 34) Mass transfer in binaries occurs when one giant swells to reach the 34) A) Roche Lobe. B) Cassini Division. C) Herbig-Haro Limit. D) Hayashi Track. E) Chandrasekhar Limit. - 5 -
35) Refer to the figure above. What is the name of the path between the points labeled 11 and 12? 35) A) asymptotic giant branch B) horizontal branch C) planetary nebula D) white dwarf E) red giant branch 36) What spectral type of star that is still around formed longest ago? 36) A) F B) A C) M D) O E) K - 6 -
37) Refer to the figure above. What is the name of the star labeled 10? 37) A) red giant branch B) asymptotic giant branch C) white dwarf D) planetary nebula E) horizontal branch 38) Isolated main-sequence stars as massive as 10 to 12 times the mass of the sun may still manage to avoid going supernova. Why? 38) A) because these stars will eject at least 4 solar masses in the planetary nebula stage B) because they would be classified as brown dwarfs C) because about half that mass will be contained in the carbon core D) because they can also have strong stellar winds E) because their masses will decrease as they fuse heavy elements into lighter elements in their cores 39) Which of the following best describes the evolutionary track followed on the H-R diagram for the most massive stars? 39) A) horizontally right, then forms a clockwise loop B) horizontally right C) horizontally right, diagonally to lower left, then horizontally right D) vertically upward, along the left edge of the diagram E) diagonally to lower right, then vertical, then horizontally left 40) What temperature is needed to fuse helium into carbon? 40) A) 100 million K B) one billion K - 7 -
C) 5,800 K D) 15 million K E) 100,000 K - 8 -