Astronomy Expert Answers & Study Resources

1.As a star exhausts hydrogen in its core, it A.becomes hotter and more luminousB.becomes hotter and less luminousC.becomes cooler and less luminousD.becomes larger in radius and hotter 2.A star will experience a helium flash ifA.it is less massive than about 3 solar massesB.its has become a red giant starC.its has formed.

63.Some young star clusters contain large numbers of T Tauri stars.64.Ninety percent of all stars fuse helium to form carbon and lie on the main sequence.65.Nuclear fusion in stars is controlled by the dependence of density on mass.66.The sun has a core in which energy travels outward primarily by radiation.67.The.

21.Based on the galaxies found in the Local Group of galaxies, the most common type of galaxy in the universe is expected to beA.the spiral galaxies.B.the barred spiral galaxies.C.the dwarf elliptical galaxies.D.the irregular galaxies.E.the giant elliptical galaxies. 22.We should expect galaxies to collide fairly often becauseA.they are large with respect to.

11.Space-time will be flat ifA.the universe is expanding.B.the universe is accelerating.C.the average density of the universe is equal to the critical density.D.the universe is finite.E.the universe is homogeneous and isotropic. 12.An open universeA.has a negative curvature.B.has zero curvature.C.has a positive curvature.D.is finite.E.has a center. 13.Current observations indicate that the amount of baryonic.

93.Elliptical galaxies contain more gas, dust and young stars than do Sa galaxies.94.Until recently, most astronomers thought elliptical galaxies were shaped like oblate spheroids.95.Cepheid variable stars are more luminous than the sun.96.The look-back time is numerically equal to the distance to a galaxy in light-years.97.The rotation curve method can be.

38.The center of our galaxy is believed to be occupied by the radio source known as ____________________.or 39.The ____________________ of the galaxy contains population I stars, open clusters, and gas clouds. 40.____________________ are groups of 100,000 to 1,000,000 population II stars firmly bound by gravity. 41.In the diagram below, the approximate absolute magnitude.

103.The Large and Small Magellanic clouds are satellites galaxies of the Milky Way.104.Elliptical galaxies are primarily made up of massive O and B stars.105.The Local Group of galaxies is dominated by the presence of spiral galaxies.106.The Milky Way galaxy is not a radio galaxy; it emits no radio radiation.107.Double-lobed radio.

31.The Virgo clusterA.is the galactic cluster that contains the Milky Way.B.is the oldest known cluster of galaxies.C.is located at the center of the universe.D.contains mostly spiral galaxies and very few elliptical galaxies.E.is a rich cluster and the closest cluster of galaxies outside of the Local Group. 32.Supermassive black holes are believed.

42.The ____________________ is that the universe is both isotropic and homogeneous. 43.The ____________________ are theories that unify the electromagnetic, weak and strong forces at extremely high energies.or 44.A(n) ____________________ universe is infinite and would have a density equal to the critical density. 45.____________________ are a form of dark matter that consists of very.

31.Which of the following can't be associated with the spiral arms of a galaxy?A.Dust and gasB.Metal poor starsC.Young, massive starsD.Star formation 32.How did Harlow Shapley determine where the center of the galaxy lies?A.He plotted the distribution of open clusters.B.He plotted the distribution of globular clusters.C.He made star counts in every direction.

21.The lowest-mass stars cannot become giants becauseA.they do not contain helium.B.they rotate too slowly.C.they cannot heat their centers hot enough.D.they contain strong magnetic fields.E.they never use up their hydrogen. 22.A planetary nebula isA.the expelled outer envelope of a medium mass star.B.produced by a supernova explosion.C.produced by a nova explosion.D.a nebula within.

21.Molecular clouds can be observedA.using infrared telescopes to detect ionized gas in the clouds.B.using x-ray telescope to observe the x-ray radiation from the molecules in the cloud.C.using radio telescopes to observe the CO emission from the clouds.D.by looking for blue wispy regions near star clusters.E.by looking for the 21-cm radiation.

45.The center of our galaxy is located in the direction of the constellation of Orion.46.Shapley found the distance to the center of the galaxy by studying the distance to open clusters.47.The disk of the Milky Way is approximately 20,000 ly in diameter.48.The rapid rotation in the outer disk suggests that.

1.Protostars are difficult to observe becauseA.the protostar stage is very short.B.they are surrounded by cocoons of gas and dust.C.they radiate mainly in the infrared.D.all of the aboveE.they are all so far away that the light hasn't reached us yet. 2.The nuclear reactions in a star's core remain under control so long.

35.All life on Earth is based on carbon chemistry.36.The DNA molecules contain six different bases.37.DNA molecules cannot be altered by chance errors in reproduction.38.The oldest fossils on Earth are more than 3 billion years old.39.The Miller experiment created synthetic DNA.40.Chemical evolution concentrated the various smaller molecules into the more stable.

114.Pulsars could not be pulsating stars because the pulses are too short.115.We expect neutron stars to spin rapidly because they conserve angular momentum.116.Many pulsars have periods that are gradually increasing as the spinning neutron stars lose energy.117.The event horizon marks the boundary within which the density is roughly the same.

31.The flatness problem states thatA.the density of the universe is very close to the critical density.B.the density of the universe is much larger than the critical density.C.the density of the universe is much less than the critical densityD.the universe is two dimensionalE.the universe is one-dimensional 32.If galaxy A is four times.

29.The portion of the electromagnetic spectrum between the 21 cm line of neutral hydrogen and the 18 cm line of OH is known as the ____________________. 30.The Miller experiment succeeded in creating ____________________. 31.The most important quantity necessary for life to form appears to be the existence of ____________________ on the surface.

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 19) How deep is an impact crater compared to its width? A) 100-200% B) 50-100% C) 30-40% D) 10-20% E) 1-10% 37) Why is Mars red? A) Its surface is made of ices that absorb blue light. B) Its atmosphere scatters blue.

1.An E galaxy containsA.mostly lower-main sequence stars and giants.B.mostly upper main sequence stars and giants.C.mostly upper main sequence stars and gas and dust.D.roughly equal numbers of upper and lower main sequence stars.E.mostly white dwarfs and supergiants. 2.A spiral (S or SB) galaxy containsA.mostly lower-main sequence stars and giants.B.mostly upper main sequence.

11.Current searches for extraterrestrial intelligence use radio telescopes at wavelengths A.which must be shorter than the local wavelengths emitted by Earth’s atmosphereB.which must be longer than the radio wavelength “noise” naturally emitted by our galaxyC.Both conditions “a” and “b” above must be fulfilled.D.Wrong! Visual light wavelengths are used because they.

73.Bok globules are small, dark fragments of the interstellar medium.74.The thermal motions of the atoms in a gas cloud can make it collapse to form a protostar.75.Molecular clouds are mapped using CO instead of hydrogen because CO is much more abundant than hydrogen in molecular clouds.76.HII regions are found near.

21.The center of our galaxy lies in the direction of (but far beyond) the stars in the constellation ofA.Ursa Minor.B.Ursa Major.C.Sagittarius.D.Orion.E.Monoceros. 22.NucleosynthesisA.is the process by which energy is produced at the center of the galaxy.B.is the process by which hydrogen and helium are converted into heavier elements.C.describes the structure of a.

83.A gas in which the pressure no longer depends on the temperature of the gas is said to be ____________________. 84.The age of a star cluster can be determined from the ____________________ of the cluster. 85.The maximum mass of a white dwarf is ____________________ solar masses. 86.A(n) ____________________ is the expulsion of the.

51.Hypernovae areA.supernovae that occur when two red dwarfs collide.B.supernovae that occur when 10 solar mass stars explode.C.supernovae that occur when stars more massive than 25 solar masses explode.D.one theory to explain the production of gamma ray bursters.E.both c and d above 52.____ occurs when light travels out of a gravitational field,.

21.The cosmic background radiation comes from a time after the origin of the universeA.when protons and neutrons were first formed.B.when the big bang first began to expand.C.the inflationary period.D.when gamma rays had enough energy to destroy nuclei.E.when electrons began to recombine with nuclei to form atoms. 22.If the universe is flatA.its.

21.The oldest fossils on EarthA.show that life began in Africa.B.show that life began in lush regions between large rivers.C.show that life began in the oceans.D.are at least 5 billion years old.E.at most 5 million years old. 22.____ shows that the building blocks of life form naturally under a wide range of.

1.The resolution of Olbers' paradox suggests that it gets dark at night becauseA.the universe is not infinite in age.B.the universe is static.C.the universe is closed.D.a and bE.all of the above 2.The assumption of isotropy states thatA.the universe looks the same at all epochs.B.the universe looks the same from all locations over.

11.____ is a form of electromagnetic radiation produced by rapidly moving electrons spiraling through magnetic fields.A.Lagrangian radiationB.AccretionC.Ultraviolet radiationD.Synchrotron radiationE.Infrared radiation 12.The Crab nebula isA.a planetary nebula.B.a Bok globule.C.an open cluster.D.an absorption nebula.E.supernova remnant. 13.Star clusters are important to our study of stars becauseA.all stars formed in star clusters.B.the sun was once a.

53.____________________ is the resistance of a gas to the flow of radiation. 54.The condition of ____________________ means that the force due to gravity pushing down on a layer is exactly equal to the pressure pushing outward on that layer. 55.Stars with masses greater than 1.1 solar masses use the ____________________ to convert.

94.Stars swell into giants when hydrogen is exhausted in their centers.95.The helium flash is the cause of some supernovae.96.Helium fusion does not begin until the star has entered the giant region of the H-R diagram.97.Even in degenerate matter, pressure depends on temperature.98.Giant and supergiant stars are rare because that stage.

11.____ of the Milky Way contains mostly old (population II) stars and globular clusters.A.The disk componentB.The spherical halo componentC.The hydrogen gas in the diskD.The spiral armsE.Sgr A* 12.____ in other galaxies should contain luminous O and B stars if they are like the Milky Way.A.The halosB.The bulgesC.The spiral armsD.The globular clustersE.The.

61.The event horizonA.is believed to be a singularity.B.is a crystalline layer.C.has a radius equal to the Schwarzschild radius.D.marks the inner boundary of a planetary nebula.E.is located at the point where synchrotron radiation is created around a pulsar. 62.An isolated black hole in empty intergalactic space would be difficult to detect becauseA.there.

61.What was the first evidence that quasars were different from astronomical objects before they were observed in visual wavelengths?A.The first quasars were seen to have fuzz.B.Quasars emitted radio energy like active galaxies, but appeared to be point sources in radio wavelengths.C.Quasars showed significant gravitational lens effects.D.The spectra of quasars looked.

47.The night sky is dark because the universe is not infinitely old.48.The cosmological principle states that any observer in any galaxy will see the same general features of the universe.49.The red shifts of the galaxies imply that the universe is expanding and that we are at the center.50.During its early.

104.Because more massive stars have more gravitational energy, they can fuse heavier nuclear fuels.105.The sun will eventually become a supernova.106.Type II supernovae are believed to occur when the cores of massive stars collapse.107.Synchrotron radiation occurs when high speed electrons move through a magnetic field.108.A Type II supernova produces a planetary.

41.For a star of Sun-like mass, what is the last stage of the nuclear fusion?A.Hydrogen to helium.B.Helium to carbon and oxygen.C.Carbon to magnesium.D.Fusion goes all the way up to iron. 42.What are the two longest stages in the life of a one solar mass star?A.Protostar, pre-main sequence.B.Protostar, white dwarf.C.Protostar, main-sequence.D.Main-sequence, white.

71.Fraud in science is rare because it is difficult to commit. Why is it difficult to commit fraud in science?A.Science requires that experimental and theoretical findings be reproducible.B.All scientists are bound by a code of ethics preventing them from publishing fraudulent work.C.Scientific results are reviewed by other scientists before they.

41.What distance method did Edwin Hubble use to determine the distance to local galaxies?A.Hubble LawB.Supernova observationsC.Period-luminosity relationship of variable starsD.Parallax 42.What distance methods is used to calibrate the Hubble constant?A.ParallaxB.Supernova observationsC.variable starsD.both a and bE.both b and c 43.What distance method is used to determine the distance to the most distant galaxies?A.Radar.

82.The units on the Hubble constant are ____________________. 83.____________________ clusters of galaxies contain closely spaced galaxies and often contain giant elliptical galaxies and a hot intergalactic medium. 84.Measuring the Doppler shift of material at various distances from the center of a galaxy can be used to construct a(n) ____________________ for that galaxy. 85.____________________.

11.A ____ generally contains well over 1000 galaxies and is quite dense. They often contain many giant elliptical galaxies.A.local groupB.poor clusterC.rich clusterD.tidal tailE.quasar 12.The Milky Way is part of I. a poor cluster. II. a rich cluster. III. the Virgo Cluster. IV. the Local Group. A.I and IIIB.I and IVC.II and IIID.II and IVE.just III 13.__________ are produced when two galaxies.

31.A type-II supernovaA.occurs when a white dwarf's mass exceeds the Chandrasekhar limit.B.is the result of helium flash.C.is characterized by a spectrum that shows hydrogen lines.D.occurs when the iron core of a massive star collapses.E.c and d 32.Synchrotron radiation is producedA.in planetary nebulae.B.by red dwarfs.C.massive stars as their iron core collapses.D.in supernova.

51.The fact that many radio lobes emit more intensely from the side away from the galaxy suggests that...A.they are formed by material falling into the galaxy.B.they are powered by magnetic fields.C.they are excited by radiation from nearby galaxies.D.they are powered by the rapid rotation of the galaxy.E.they are created by.

1.A cell's DNA molecules are constructed ofA.amino acids.B.proteins.C.sugars, phosphates, and bases.D.all of the aboveE.none of the above 2.DNA molecules contain patterns for the production ofA.proteins.B.amino acids.C.phosphates and sugars.D.four kinds of bases.E.all of the above 3.The first complex life appeared on Earth about 0.5 billion years ago during theA.Jurassic Period.B.Mississippian Period.C.Cambrian Period.D.Precambrian Period.E.Neolithic.

1.Who first calibrated the Cepheid variable stars for use in determining distance?A.Henrietta LeavittB.Edwin HubbleC.John GlennD.Carl SaganE.Harlow Shapley 2.Which of the following is not a characteristic of the stars of the disk component of our galaxy?A.circular orbitsB.randomly inclined orbitsC.higher metal abundanceD.young starsE.star formation regions 3.A group of 10 to 100 stars that formed.

41.What force(s) are responsible for the collapse of an interstellar cloud?A.nuclearB.gravityC.electricD.magneticE.both c and d 42.Star clusters are important to the study the stellar evolution because stars in a given cluster have the sameA.temperature.B.mass.C.age.D.luminosity. 43.Why do higher mass stars live shorter lives on the main sequence than lower mass stars?A.Higher mass stars burn.

11.The lower edge of the Main Sequence band is known as ____ and represents the location in the HR-diagram at which stars begin their lives as main sequence stars.A.the Coulomb barrierB.hydrostatic equilibriumC.the birth lineD.the zero-age main sequenceE.the evolutionary track 12.____ is the thermonuclear fusion of hydrogen to form helium operating in.

77.To observe a visual binary, we must measure radial velocities. 78.The more massive star in a binary system is always farthest from the center of mass. 79.If a binary system has a period of 4 years and a separation of 5 AU, then the total mass is 7.8 solar masses. 80.To observe a.

31.Stars are born inA.reflection nebulae.B.dense molecular clouds.C.HII regions.D.the intercloud medium.E.the local bubble. 32.Absorption lines due to interstellar gasA.are wider than the lines from stars because the gas is hotter than most stars.B.are more narrow than the lines from stars because the gas has a lower pressure than stars.C.indicate that the interstellar.

71.If Hubble's constant is taken to be 70 km/sec/Mpc, and a quasar is found with a radial velocity of 0.95 times the speed of light, how far away is the quasar?A.4100 MpcB.0.014 MpcC.67 MpcD.74 MpcE.300,000 Mpc 72.If a quasar has a recessional velocity of 2.7´105 km/sec and is determined to be.