Astro 10 Exam 3
The surface of the Sun is about ______ and the core is about _______. A) 6000K / 15 million K B) 11000K / 27 million K C) Depleted / to explode D) All of the above
A) 6000K / 15 million K
How do a prominence and a flare differ? A) A prominence is a huge plume of glowing gas trapped in the Sun's magnetic field; a flare is a brief, bright eruption in the chromosphere. B) A prominence is brief, bright eruption in the chromosphere; a flare is a tenuous flow of hydrogen and helium that sweeps across the Solar System. C) A prominence is a jet of hot gas thousands of kilometers long; a flare is an immense bubble of hot gas rising from deep within the Sun. D) There is no difference.
A) A prominence is a huge plume of glowing gas trapped in the Sun's magnetic field; a flare is a brief, bright eruption in the chromosphere.
What holds the Sun together? A) Its gravity. B) Its magnetic field. C) The pressure of the solar wind. D) The collective gravity of the planets. E) None of the above.
A) Its gravity.
Which of the following is evidence that solar activity affects Earth's climate? A) The Maunder minimum - a period of abnormally low sunspot numbers - coincided with abnormally cold northern winters B) The Schwab Cycle - a period of abnormally numerous and large sunspots - preceded a 250 year drought in Africa. C) The dust bowl of the 1930's in the United States coincided with the complete disappearance of sunspots during that time. D) All of the above.
A) The Maunder minimum - a period of abnormally low sunspot numbers - coincided with abnormally cold northern winters
What is the Sun's outermost atmosphere called? A) The corona B) The chromosphere C) The photosphere D) The radiative zone
A) The corona
Which of the following is not a property of the outer planets (excluding Pluto)? A) They all have solid surfaces for spacecraft to land on. B) They are composed mostly of hydrogen and helium. C) They all have rings. D)They are all far more massive than the Earth.
A) They all have solid surfaces for spacecraft to land on.
What do astronomers call the shell of ejected gas from certain low mass stars? A)..A planetary nebula. B)..A Supernova. C)..A bipolar flow. D)..A protostar. E)..A Cepheid variable.
A).. A planetary nebula.
Why does a high mass star evolve differently than a low mass star? A)... It can burn more fuels because its core can get hotter. B)... It has more material to burn so can last longer. C)...It is so bright that it drives material in space away from it so it can't gather up more fuel. D)...It has a lower gravity so it can't pull in more fuel from space. E)...The statement is false. High and low mass stars evolve the same way.
A)... It can burn more fuels because its core can get hotter.
When a star has stopped contracting and settled down, where is it in the HR diagram? A)... On the main sequence. B)... Below the main sequence in the lower left. C)... In the upper right as a red giant. D)...It is not on the H-R diagram at that time. E)... In the instability strip.
A)... On the main sequence.
A young blue star moving along a circular orbit in the disk is a A)... Pop I star. B)... Pop II star. C)... Pop X star.
A)... Pop I star.
Which of the following gives evidence of the solar wind? A)... The tails of comets. B)... Jet streams on Earth. C)... Solar prominences. D)... Solar flares. E)...Sunspots.
A)... The tails of comets.
A star that is cool and very luminous must have A)... a very large radius. B)... a very small radius. C)... a very small mass. D)... a very great distance. E)... a very low velocity.
A)... a very large radius.
The modified form of Kepler's third law allows astronomers to determine the Milky Way's A)... mass. B)... age. C)... composition. D)... shape. E)... number of spiral arms.
A)... mass.
What fuel do stars on the main sequence burn? A)...Hydrogen B)... Helium C)...Carbon D)...Iron E)...Uranium
A)...Hydrogen
Why does the Sun give off light? A)...It is hot.. B)... It is highly reflective. C)...It is a hole in space through which we see many distant stars. D)...Meteorites are constantly hitting its surface and emitting flashes of light. E)...All of the above contribute.
A)...It is hot..
How do we know sunspots have magnetic fields? A)...The Zeeman effect. B)... Wien's law. C)... The Hubble effect. D)... Compasses on Earth point toward them. E)... Comet tails point toward them.
A)...The Zeeman effect.
If a spinning object's radius shrinks by a factor of 5, its rotation velocity will A)...get five times faster. B)... get five times slower. C)...remain the same. D)...get 10 times faster. E)...get 25 times faster.
A)...get five times faster.
If the Sun were to shrink its radius by a factor of 100 it would be about the size of A)...the Earth. B)... Jupiter. C)...the state of Texas. D)...a small town. E)...a house.
A)...the Earth.
What are the third, fifth and seventh planets in order of increasing distance from the Sun? A) Venus, Earth, Jupiter B) Earth, Jupiter, Uranus C) Mercury, Mars, Saturn D) Mars, Jupiter, Neptune
B) Earth, Jupiter, Uranus
Which of the following is an outer planet? A) Earth B) Jupiter C) Mars D) Venus
B) Jupiter
What is solar seismology? A) The study of the Sun's atmosphere by analyzing waves in the Sun's interior. B) The study of the Sun's interior by analyzing waves in the Sun's atmosphere. C) The study of gravitational waves from the Sun. D) The study of the Sun's changing size.
B) The study of the Sun's interior by analyzing waves in the Sun's atmosphere.
Why are astronomers interested in detecting neutrinos from the Sun? Neutrinos A) can reveal the Sun's inner magnetic field. B) give information about the nuclear reactions in the Sun's core. C) prove the Sun will explode in a few thousand years D) prove the Sun is only about 2 million years old.
B) give information about the nuclear reactions in the Sun's core.
One reason the planets near the sun are composed mainly of rock and iron may be that A) the Sun's magnetic field attracted all the iron into the region around the Sun. B) the Sun's heat made it difficult for ices and gases to condense near it. C) the Sun's gravity sucked in iron and heavy material and the lighter materials floated farther away. D) the Sun is made mostly of iron, so the planets nearest it are formed of iron.
B) the Sun's heat made it difficult for ices and gases to condense near it.
The sun's energy comes from A) the release of magnetic energy. B) the conversion of mass into energy. C) its rotation slowing down. D) meteors and asteroids striking its surface.
B) the conversion of mass into energy.
What chemical element does the Sun make in burning its last fuel? A)...Helium. B)... Carbon. C)...Neon. D)...Silicon. E)...Iron.
B)... Carbon.
Why does heat flow from the Sun's core to its surface? A)... Gravity of the planets pulls it up and out. B)... Heat always flows from hot to cool regions. C)... Magnetic repulsion in the Sun's core. D)... The Sun's spin. E)... The Coriolis force.
B)... Heat always flows from hot to cool regions.
What brings a star to the end of its life? A)... It begins to spin so slowly that it collapses. B)... It runs out of fuels it can "burn." C)... All its magnetic energy leaks away. D)... It eventually collides with another star and smashes to pieces. E)... It gets sucked into a black hole.
B)... It runs out of fuels it can "burn."
What powers the Sun? A)... Chemical burning of hydrogen and oxygen. B)... Nuclear fusion of hydrogen into helium. C)... Nuclear fission of helium into hydrogen. D)... The breakdown of neutrinos. E)... Friction as it moves through the gases of space.
B)... Nuclear fusion of hydrogen into helium.
The Sun at present rotates once per month. If its rotation speed increased by a factor of 100 and its radius shrank by a factor of 100 how often would it spin? Hint: A month is about 5x104 minutes. A)...Once every 5 days. B)... Once every 5 minutes. C)...Once every 5 years. D)...Once every 15 minutes. E)...Once every 50 minutes.
B)... Once every 5 minutes.
Why does fuel "burn" only in a star's core? A)...The fuel settles to the core. B)... Only the core is hot enough for fusion. C)...Only the core spins fast enough. D)...The statement is incorrect. Fuels "burn" just below the surface. E)...The statement is true but none of the above are the correct answer.
B)... Only the core is hot enough for fusion.
A spiral galaxy has a small bright central region and its spectrum shows that it contains hot, rapidly moving gas. It is most likely a ____________ galaxy. A)... barred spiral B)... Seyfert C)... radio D)... BL Lac E)... quasar
B)... Seyfert
What are the dark things (labeled A) in the figure above called? A)... Prominences. B)... Sunspots. C)... Flares. D)... Craters. E)... Solar rilles.
B)... Sunspots.
What quantities are plotted in an H-R diagram? A)...Density and distance. B)... Temperature and luminosity. C)...Radius and luminosity. D)...Mass and volume. E)...None of the above.
B)... Temperature and luminosity.
Why does the star's core get hotter as the core shrinks? A)...The fuels settle there to liberate their heat. B)... The core is compressed and compression heats a gas. C)...The core spins faster and friction heats it. D)...The statement is false. A shrinking core cools. E)...The statement is true but none of the above are correct explanations of why.
B)... The core is compressed and compression heats a gas.
Why do astronomers think that some of the x-ray sources they observe are associated with black holes rather than neutron stars in orbit around a normal star? A)... They can see a tiny black dot with the x-ray telescope. B)... The mass of the unseen object inferred from its orbital motion is too large to be a neutron star. C)... The mass of the unseen object inferred from its orbital motion is too small to be a neutron star. D)... The magnification of the x-rays by the black hole's gravitational lens clearly shows the black hole.
B)... The mass of the unseen object inferred from its orbital motion is too large to be a neutron star.
Why are these regions dark? A)... They absorb light better than the surrounding gas. B)... They are cooler than the surrounding gas. C)... Cool clouds above the Sun's surface block our view. D)... There are clouds of iron vapor ejected from the Sun's core. E)... There are high altitude clouds in our atmosphere.
B)... They are cooler than the surrounding gas.
The law of conservation of angular momentum states that when an object of a fixed mass changes its radius R, its rotation velocity, V, will change so that A)...V/R = constant. B)... VR = constant. C)...R/V = constant. D)...V2R = constant. E)... R2V = constant.
B)... VR = constant.
As a star like the Sun evolves into a red giant, its core A)... expands and cools. B)... contracts and heats. C)...expands and heats. D)... turns into iron. E)...turns into uranium.
B)... contracts and heats.
Stars like the Sun probably do not form iron cores during their evolution because A)... all the iron is ejected when they become planetary nebulas. B)... their cores never get hot enough for them to make iron by nucleosynthesis. C)...the iron they make by nucleosynthesis is all fused into uranium. D)... their strong magnetic fields keep their iron in their atmospheres. E)... None of the above.
B)... their cores never get hot enough for them to make iron by nucleosynthesis.
If a planetary nebula expands at about 20 km/sec, how big in AU's will it get in 10,000 years? Note: Assume it starts with zero radius and that it expands at a constant speed. You can take the number of seconds in a year to be 3x107 and the number of km in an AU to be 1.5x108. A)...400 AU. B)...40,00 AU. C)...60,000 AU. D)...3,000 AU. E)...3 million AU.
B)...40,00 AU.
What causes the radio pulses of a pulsar? A)... The star vibrates. B)...As the star spins, beams of radio radiation from it sweep through space. If one of these beams points toward the Earth, we observe a pulse. C)... The star undergoes nuclear explosions that generate radio emission. D)... The star's dark orbiting companion periodically eclipses the radio waves emitted by the main star. E)... A black hole near the star absorbs energy from it and reemits it as radio pulses.
B)...As the star spins, beams of radio radiation from it sweep through space. If one of these beams points toward the Earth, we observe a pulse.
What is the last fuel the Sun will be able to burn? A)...Hydrogen. B)...Helium. C)...Neon. D)...Iron. E)...Uranium.
B)...Helium.
Why does a massive star end up with a core so different from that of a low mass star? A)... Its greater gravity allows it to pull the heavier elements to the core, much like has happened in the Earth. B)...Its greater gravity compresses the core more and makes it hotter, allowing heavier atoms to fuse. C)...Its greater gravity compresses the core more and makes it cooler, preventing the fusion of heavier atoms. D)... It contains more matter so it has more iron that can settle out. E)... Trick Question. There is essentially no difference between the core of high and low mass stars.
B)...Its greater gravity compresses the core more and makes it hotter, allowing heavier atoms to fuse.
What of the following most directly determines how much fuel a star has? A)...Its density. B)...Its mass. C)...Its temperature. D)...Its luminosity. E)...Its speed of rotation.
B)...Its mass.
In what part of the H-R diagram do white dwarfs lie? A)... Upper left B)...Lower center C)... Upper right D)...Lower right E)... just above the Sun on the Main Sequence.
B)...Lower center
Why are supernova explosions important for our existence? A)...They heat the interstellar medium and help keep Earth warm. B)...They liberate from the star's core the heavy elements of which we and Earth are made. C)...They destroy wandering stars that might otherwise collide with our Sun. D)...They bathe Earth in x-rays that may have helped life form. E)...They sterilized the young Earth and allowed life to originate by killing off competing bacteria.
B)...They liberate from the star's core the heavy elements of which we and Earth are made.
One way astronomers deduce that the Milky Way has a disk is that they A).. see stars arranged in a circular region around the north celestial pole. B)..see far more stars along the band of the Milky Way than in other directions. C).. see a large dark circle silhouetted against the Milky Way in the Southern hemisphere. D).. see the same number of stars in all directions in the sky. E).. None of the above.
B)..see far more stars along the band of the Milky Way than in other directions.
Approximately how old is the Solar System? A) 4.5 thousand years. B) 4.5 million years. C) 4.5 billion years. D) 4.5 trillion years.
C) 4.5 billion years.
The Sun is composed of about ______ and _______ plus 2% other elements. A) 71% helium / 27% hydrogen B) 50% hydrogen / 50% helium C) 71% hydrogen / 27% helium D) 77% nitrogen / 22% oxygen
C) 71% hydrogen / 27% helium
How do we know the interior composition of Jupiter? A) Astronomers examined Jupiter's spectrum. B) Astronomers studied earthquake waves using instruments on Jupiter's surface. C) Astronomers calculated Jupiter's average density and compared it to those of abundant candidate materials, taking gravitational compression into account. D) All of the above.
C) Astronomers calculated Jupiter's average density and compared it to those of abundant candidate materials, taking gravitational compression into account.
What holds the Sun together? A) Electrostatic forces between ions in its interior. B) Gas pressure. C) Its gravitational force. D) Nothing: the Sun is actually expanding very slowly.
C) Its gravitational force.
A huge interstellar cloud collapsed into a rotating disk with a central bulge. What was this? A) The disk was the solar nebula and the bulge became Jupiter. B) A large belt containing asteroids in a gap between the orbits of Mars and Jupiter. C) The disk was the solar nebula and the bulge became the Sun. D) The formed the outer planets which eventually met up with the Sun.
C) The disk was the solar nebula and the bulge became the Sun.
What is the visible surface of the Sun called? A) The corona B) The chromosphere C) The photosphere D) The radiative zone
C) The photosphere
What is the specific 3-step energy generating process in the Sun called? A) Hydrostatic equilibrium B) Thermography. C) The proton-proton chain. D) Radiative transfer.
C) The proton-proton chain.
Why do sunspots appear dark? A) They are made of different material than the surrounding gas. B) They are hotter than the surrounding gas. C) They are cooler than the surrounding gas. D) Their magnetic fields block light.
C) They are cooler than the surrounding gas.
All planets spin in the same direction except for A) Mercury, Earth, and Jupiter. B) Venus, Mars, and Saturn. C) Venus, Uranus, and Pluto. D) Neptune, Uranus, and Pluto.
C) Venus, Uranus, and Pluto.
A planet's average density is equal to its __ divided by its __. A) mass, surface area B) volume, mass C) mass, volume D) mass, radius
C) mass, volume
The Sun produces its energy through A) the fusion of neutrinos into helium. B) the fusion of positrons into hydrogen. C) the fusion of hydrogen into helium. D) electric currents generated in its core.
C) the fusion of hydrogen into helium.
What is meant by an accretion disk? A)... Hot gas ejected from a supernova. B)... Cold gas falling onto a white dwarf and forming a flat "splotch" on its surface. C)... Gas orbiting around a black hole or star. D)... Matter spun off a neutron star as it collapses. E)... All of the above.
C)... Gas orbiting around a black hole or star.
Why does the number of sunspots change over time? A)...Nuclear reactions switch on and off in its core. B)... Meteor showers that form the spots come and go. C)... The Sun's magnetic field strengthens and weakens. D)...The Moon's phase disturbs the Sun's surface. E)... The Sun's rotation alternatively shows us its hot and cool side.
C)... The Sun's magnetic field strengthens and weakens.
What evidence leads astronomers to believe that they have detected black holes? A)...They have seen tiny dark spots drift across the face of some distant stars. B)... They have detected pulses of ultraviolet radiation coming from within black holes. C)... They have seen x-rays, perhaps from gas around a black hole, suddenly disappear as a companion star eclipses the hole. D)...They have seen a star suddenly disappear as it was swallowed by a black hole. E)...They have looked into a black hole with x-ray radar telescopes.
C)... They have seen x-rays, perhaps from gas around a black hole, suddenly disappear as a companion star eclipses the hole.
The change in rotation rate of spinning object caused by its size change is a consequence of A)... conservation of magnetic energy. B)...the law of action-reaction. C)... conservation of angular momentum. D)...the special theory of relativity. E)...None of the above.
C)... conservation of angular momentum.
The Sun rotates now with a rotation speed of about 2 km/sec. If its radius shrank to the size of the Earth, about how fast would it spin? A)...20 km/sec. B)... 2000 km/sec. C)...200 km/sec. D)...0.2 km/sec. E)...400 km/sec.
C)...200 km/sec.
What is the remnant core of a low mass star like the Sun mostly made of? A)... Hydrogen. B)...Helium. C)...Carbon. D)...Sulfur. E)...Iron.
C)...Carbon.
What happens to the core of a low mass star that ejects its outer layers.? A)...It becomes a black hole. B)... It becomes a neutron star. C)...It becomes a white dwarf. D)... It becomes a pulsar. E)...It becomes a cepheid variable.
C)...It becomes a white dwarf.
What happens to a low mass star when it finally uses up the helium in its core? A)...It begins to burn iron. B)... It simply cools and dims. C)...It ejects its outer layers. D)...The core collapses and it blows up as a supernova. E)...The whole star collapses and becomes a neutron star.
C)...It ejects its outer layers.
What makes a gas cloud contract to form stars? A)... Its magnetic field. B)...The dust in it is drawn together by static electricity. C)...Its gravity draws it inward. D)...Pressure from meteor collisions squeezes it inward. E)... Uranium atoms attract lead atoms by nuclear fusion.
C)...Its gravity draws it inward.
What allows a high mass star to burn different fuels than a low mass star? A)... Its greater mass means that it contains more fuels. B)... More mass means a stronger magnetic field that helps heavier fuels burn. C)...More mass means more compression and thus a hotter core that allows heavier fuels to burn. D)...High mass stars spin slower and thus do not mix their fuels as well. E)...The statement is false. Low and high mass stars can burn the same fuels.
C)...More mass means more compression and thus a hotter core that allows heavier fuels to burn.
What makes a star shine? A)...Reflected light from the galaxy. B)...Radioactive decay of elements in its core. C)...Nuclear Fusion of light elements. D)... Nuclear Fission of heavy elements. E)...None of the above.
C)...Nuclear Fusion of light elements.
What happens to the star's outer layers as the fuel in its core is used up? A)...They shrink and cool. B)... They shrink and heat up. C)...They expand and cool. D)...They expand and heat up. E)...Nothing. Only the interior changes.
C)...They expand and cool.
A planetary nebula is A)... another term for the disk of gas around a young star. B)... the cloud from which protostars form. C)...a shell of gas ejected from a star late in its life. D)...what is left when a white dwarf star explodes as a supernova. E)...the remnants of the explosion created by the collapse of the iron core in a massive star.
C)...a shell of gas ejected from a star late in its life.
Which of the following features of the Solar System does the solar nebula hypothesis explain? A) All the planets orbit the Sun in the same direction. B) All the planets' orbits lie in nearly the same plane. C) The planets nearest the Sun contain only small amounts of substances that condense at low temperatures. D) All of the above.
D) All of the above.
What do we call the swarm of comet nuclei in a huge shell surrounding the Sun and planets? A) The Solar System B) The asteroid belt C) The ecliptic. D) The Oort Cloud.
D) The Oort Cloud.
How big is the Sun compared to the Earth, approximately? A)... 5 times bigger. B)... 15 times bigger. C)... 500 times bigger. D)... 100 times bigger. E)... 1000 times bigger.
D)... 100 times bigger.
The density of the Sun is presently about 1 gm/cm3. If the Sun's radius shrank to about the size of the Earth, (About a factor of 100), what would its density be? A)... About 10 gm/cm3. B)... About 100 gm/cm3. C)... About 1000 gm/cm3. D)... About 106 gm/cm3. E)... About 10,000 gm/cm3.
D)... About 106 gm/cm3.
Which of the following is responsible for making a pulsar pulse? A)... Nuclear reactions. B)... Radiation trapping in its atmosphere. C)... Vibrations triggered by a companion. D)... Spinning. E)... Tidal distortions caused by a companion.
D)... Spinning.
When a spinning object changes its size, its rotation rate A)...remains the same. B)...always increases. C)...always decreases. D)... increases or decreases, depending on whether it shrinks or expands.
D)... increases or decreases, depending on whether it shrinks or expands.
How long is it between peaks in the number of sunspots? A)...11 months. B)...5 years. C)... 2.5 years. D)...11 years. E)... 111 years.
D)...11 years.
What determines how rapidly a star burns up its fuel? A)...Its mass. B)... Its luminosity. C)... Its location in the Milky Way. D)...Both A) and B) E)...None of the above.
D)...Both A) and B)
What happens to the star's core as the hydrogen there is used up? A)... Nothing. It just turns to helium. B)...It expands and cools. C)...It contracts and cools. D)...It contracts and heats. E)...As the helium accumulates the core rises to the surface of the star and escapes into space.
D)...It contracts and heats.
What makes a star stop contracting? A)... Its magnetic field. B)... The dust in it gets packed so tightly. C)...Its gravity gets too strong. D)...It gets hot enough that its pressure builds up. E)... It gets cool enough that it freezes.
D)...It gets hot enough that its pressure builds up.
The Sun is supported against the crushing force of its own gravity by A)...magnetic forces. B)... its rapid rotation. C)... the force exerted by escaping neutrinos. D)...gas pressure. E)... the antigravity of its positrons.
D)...gas pressure.
A star has a parallax of 0.04 arc seconds. What is its distance? A)..4 light years B)..4 parsecs C).. 40 parsecs D)..25 parsecs E)..250 parsecs
D)..25 parsecs
Which of the following has a radius (linear size) closest to that a neutron star? A).. The Sun. B)..The Earth. C).. A basketball. D)..A small city. E)..A gymnasium.
D)..A small city.
A large galaxy contains mostly old (Pop II) stars spread smoothly throughout its volume, but it has little dust or gas. What type galaxy is it most likely to be? A).. Irr B)..S C).. SB D)..E E)..All of the above are possible.
D)..E
A star whose mass is 5 times larger than the Sun's and whose luminosity is 100 times larger than the Sun's has a main-sequence lifetime about A)... 5 times longer than the Sun's. B)... 500 times longer than the Sun's. C)... 5 times shorter than the Sun's. D)... 100 times shorter than the Sun's. E)... 20 times shorter than the Sun's.
E)... 20 times shorter than the Sun's.
When a high mass star's core collapses the star _________. A)...explodes as a supernova. B)...becomes a white dwarf. C)... becomes a neutron star. D)...becomes a black hole. E)... All of the above except B are possible outcomes.
E)... All of the above except B are possible outcomes.
Astronomers know that interstellar matter exists because A)... they can see it in dark clouds and clouds that absorb light. B)... the matter creates narrow absorption lines in the spectra of some stars. C)... they can detect radio waves coming from atoms and molecules in the cold gas. D)... spacecraft have sampled clouds near Orion. E)... All the above except (D).
E)... All the above except (D).
Astronomers believe that dark matter exists because A)... they can detect it with radio telescopes. B)... the outer parts of galaxies rotate faster than expected on the basis of the material visible in them. C)... the galaxies in clusters move faster than expected on the basis of the material visible in them. D)... it is the only way to explain the black holes in active galaxies. E)... Both (B) and (C) are correct.
E)... Both (B) and (C) are correct.
If mass is added to a white dwarf, A)... its radius increases. B)... its radius decreases. C)... its density increases. D)... it may exceed the Chandrasekhar limit and collapse. E)... all of the above except (a).
E)... all of the above except (a).
The Local Group A)... contains about 30 member galaxies. B)... is a poor cluster. C)... is the galaxy cluster to which the Milky Way belongs. D)...is a rich cluster. E)... is all of the above except (D).
E)... is all of the above except (D).
How does this compare to the size of the Solar System out to Pluto? A)... About 10 times larger. B)...100 times smaller. C)...10,000 larger. D)...10 million times larger. E)...1000 times larger.
E)...1000 times larger.
A galaxy's spectrum has a redshift of 30,000 kilometers per second. If the Hubble constant is 75 kilometers per second per megaparsec, how far away from Earth is the galaxy? A)...106 megaparsecs B)... 1000 megaparsecs C)...20 megaparsecs D)...50 megaparsecs E)...400 megaparsecs
E)...400 megaparsecs
A star radiates most strongly at 400 nanometers. What is its surface temperature? A)...400 K B)...4000 K C)...40.000 K D)...75,000 K. E)...7500 K
E)...7500 K
What kind of object does a main sequence star become on first using up its core hydrogen? A)...A white dwarf. B)...A protostar. C)... A supernova. D)...A planetary nebula. E)...A red giant.
E)...A red giant.
Astronomers think the Milky Way has spiral arms because A)...they can see them unwinding along the celestial equator. B)... radio maps show that gas clouds are distributed in the disk with a spiral pattern. C)...young star clusters, HII regions, and associations outline spiral arms. D)...globular clusters outline spiral arms. E)...Both (B) and (C) are correct.
E)...Both (B) and (C) are correct.
What do astronomers think the core of a massive star is made of when it reaches the end of its life? A)...Hydrogen. B)...Helium. C)... Carbon. D)... Sulfur. E)...Iron.
E)...Iron.
The Schwarzschild radius of a body is A)... the distance from its center at which nuclear fusion ceases. B)... the distance from its surface at which an orbiting companion will be broken apart. C)... the maximum radius a white dwarf can have before it collapses. D)... the maximum radius a neutron star can have before it collapses. E)...the radius of a body at which its escape velocity equals the speed of light.
E)...the radius of a body at which its escape velocity equals the speed of light.
From what do stars form? A)..Globular clusters. B)..Open clusters. C).. Black holes. D)..Planetary nebulas. E)..Interstellar clouds.
E)..Interstellar clouds.
Which of the following sequences below correctly describes the evolution of the Sun from young to old? A).. White dwarf, red giant, main-sequence, protostar B)..Red giant, main-sequence, white dwarf, protostar C).. Protostar, red giant, main-sequence, white dwarf D)..Protostar, main-sequence, white dwarf, red giant E)..Protostar, main-sequence, red giant, white dwarf
E)..Protostar, main-sequence, red giant, white dwarf
How many stars are there in the Solar System? A) 0 B) 1 C) 9 D) 100 billion
B) 1
About how long is the solar cycle (evidenced by sunspots)? A) 3 years B) 5 days C) 11 years D) 33 years
C) 11 years
The Sun is about how far from Earth? A) 380,000 km B) 93,000,000 km. C) 150,000,000 km. D) One light year.
C) 150,000,000 km.
Which of the following stars is hottest? A)... An M star. B)... An F star. C)... A G star. D)... A B star. E)... An O star.
E)... An O star.
After the first 20 billion years of the universe, the Sun will have evolved through red giant, main sequence, and white dwarf stages. Assuming a current radius of 1, what radii will the Sun have during these phases, in correct order? a) 1, 400, 0.01 b) 0.01, 1, 400 c) 1, 1, 1 d) 1, 0.01, 400
a) 1, 400, 0.01
Consider two stars in constellation Pasta: Alpha Tortellini - bright in UV, dim in IR Beta Ziti - dim in UV, bright in IR There is little or no dust along the line of sight to Pasta. Which star is hotter? a) Alpha Tortellini b) Beta Ziti c) Both are the same temperature.
a) Alpha Tortellini
Evidence for an association between interstellar dust and star formation comes from a) dark clouds that attenuate the light from background stars. b) emission at radio wavelengths of 21cm. c) stars that appear redder than expected from their spectral type. d) bright nebulae with redshifted emission lines. (Note: More than one answer may apply.)
a) dark clouds that attenuate the light from background stars. c) stars that appear redder than expected from their spectral type.
An observer far outside our galaxy would best describe our galaxy and the Sun's position in it as a a) disk of stars with our Solar System near the edge. b) disk of stars centered on our Solar System. c) disk of stars with a bulge containing our Solar System. d) sphere of stars centered on our Solar System. e) sphere of stars with our Solar System near the edge.
a) disk of stars with our Solar System near the edge.
If the material in the primordial Solar System retained its angular momentum as it collapsed to form the Sun, the Sun's rotation rate should be a) fast (less than a week). b) moderate (a week to a month). c) slow (more than a month). d) zero (non-rotating).
a) fast (less than a week).
In a certain spectroscopic binary, one star's spectral lines vary in wavelength twice as much as the other. The star whose lines move more is a) half the mass of the other. b) twice the mass of the other. c) twice as far from Earth as the other. d) twice as luminous as the other.
a) half the mass of the other.
The most likely reason that clusters of galaxies have more elliptical than spiral galaxies is that in the high density cluster environment a) spirals merge to form ellipticals. b) intracluster gas strips galaxies of the gas needed for star formation. c) near-misses between galaxies makes them rounder. d) galaxies are older and their brighter disk stars have burned out.
a) spirals merge to form ellipticals.
When we observe stars near the center of the Milky Way Galaxy, we detect light that was emitted from those stars about a) 200 million years ago. b) 25,000 years ago. c) 8 years ago. d) 8 minutes ago. e) when the galaxy was formed.
b) 25,000 years ago.
The factors that tend to resist collapse in a gas cloud are I. the magnetic field of the cloud II. the presence of supernovae near the gas cloud III. the existence of molecules in the gas IV. heat in the gas V. the rotation of the cloud a) I, III, V. b) I, IV, V. c) II, III, IV. d) II, IV, V. e) III, IV, V.
b) I, IV, V.
Which of the following would lengthen the amount of time a star is able to fuse hydrogen at its center? a) The temperature in the core of the star is increased. b) The gas in the core of the star is enriched in hydrogen. c) The mass of the star is increased. d) none of the above
b) The gas in the core of the star is enriched in hydrogen.
Why does fusion of hydrogen release energy? a) Fusion breaks the electromagnetic bonds between hydrogen atoms, releasing energetic photons. b) The mass of a helium nucleus is smaller than the mass of four protons. c) The mass of a helium nucleus is larger than the mass of four protons. d) The velocity of four protons is larger than the velocity of a helium nucleus. e) None of the above are true.
b) The mass of a helium nucleus is smaller than the mass of four protons.
Which of the following stars is probably oldest? a) a 1 solar mass main sequence star b) a 1 solar mass white dwarf c) a 10 solar mass main sequence star d) a 10 solar mass red giant
b) a 1 solar mass white dwarf
Sunspots appear dark because they are a) holes in the photosphere through which you can see deeply into the stellar interior. b) a bit cooler and thus dimmer than the rest of the photosphere. c) large opaque structures that block light from the glowing solar surface. d) causing retinal damage.
b) a bit cooler and thus dimmer than the rest of the photosphere.
As a star cluster evolves over time, a) the composition of the stars in the cluster changes from metal-poor to metal-rich. b) more and more main-sequence stars become red giants. c) the cluster changes its location in the galaxy, getting closer to the spiral arms. d) the shape of the cluster changes to a disk shape.
b) more and more main-sequence stars become red giants.
Narrow absorption lines in the spectra of distant quasars could be caused by clouds of gas on the a) near side of the quasar with large random velocities but small bulk velocities. b) near side of the quasar with small random velocities but large bulk velocities. c) far side of the quasar with large random velocities but small bulk velocities. d) far side of the quasar with small random velocities but large bulk velocities.
b) near side of the quasar with small random velocities but large bulk velocities.
Compared to the Sun, most other stars in the Milky Way Galaxy are a) as small relative to the Sun as they appear in the sky. b) smaller. c) about the same size. d) much larger.
b) smaller.
Two stars have the same chemical composition, spectral type, and luminosity class, but one is 10 light years from the Earth and the other is 1000 light years from the Earth. The farther star appears to be a) 10 times fainter. b) 100 times fainter. c) 10,000 times fainter. d) 100,000,000 times fainter. e) the same brightness since the stars are identical.
c) 10,000 times fainter.
Two stars have the same surface temperature, but the radius of one is 100 times that of the other. The larger star is a) 10 times more luminous. b) 100 times more luminous. c) 10,000 times more luminous. d) 100,000,000 times more luminous. e) the same luminosity.
c) 10,000 times more luminous.
If the Sun were the size of a tennis ball (6.35 cm in diameter) then the red giant star Betelgeuse would have a diameter of a) 2.3 cm, about the size of a ping pong ball. b) 23 cm, about the size of a basketball. c) 23 m, larger than the equivalent size of Mars' orbit. d) 23 km.
c) 23 m, larger than the equivalent size of Mars' orbit.
Two stars have the same temperature, but the radius of one is twice that of the other. How much brighter is the larger star? a) the same because luminosity depends only on temperature. b) 2 times c) 4 times d) 8 times e) 16 times
c) 4 times
Why would two protons combine to form an atom of deuterium (heavy hydrogen) in the core of a star like the Sun? a) The electromagnetic force strongly attracts the protons. b) The gravitational force strongly attracts the protons. c) The velocity of protons in the core of the Sun is very large. d) Protons never combine to form deuterium in the core of the Sun. e) Both a and c.
c) The velocity of protons in the core of the Sun is very large.
Stars are a) solid. b) liquid. c) gaseous. d) mostly carbon, oxygen, nitrogen, and iron. e) both c and d.
c) gaseous.
Fusion in the core of a stable massive star cannot proceed beyond iron because a) it would require temperatures that even stars cannot generate. b) the fusion of iron nuclei is impossible under any circumstances. c) iron nuclei are the most tightly bound of all nuclei so iron fusion does not release energy. d) the Chandrasekhar limit has been reached, so a black hole must result.
c) iron nuclei are the most tightly bound of all nuclei so iron fusion does not release energy.
Because stars in clusters all have similar age and distance, the main underlying physical cause of their different appearances is their a) color. b) radius. c) mass. d) chemical composition. e) temperature.
c) mass.
If two stars are on the main sequence, and one is more luminous than the other, we can be sure that the a) more luminous star will have the longer lifetime. b) fainter star is the more massive. c) more luminous star is the more massive. d) more luminous star will have the redder color.
c) more luminous star is the more massive.
The Sun's luminosity comes primarily from a) chemical burning. b) the mechanical energy of turbulence. c) nuclear fusion. d) gravitational contraction. e) all of the above are comparable in importance.
c) nuclear fusion.
Trigonometric parallax, the apparent motion of stars due to the Earth's annual motion around the Sun, can be used to study the structure of our galaxy a) within the Solar System. b) up to about 1 parsec (3.26 light years) from the Sun. c) within about 100 parsecs of the Sun. d) within about 100 parsecs of the galactic center.
c) within about 100 parsecs of the Sun.
The powerful nuclei of quasars and Seyfert galaxies cannot be dominated by starlight because nuclear fusion in a group of stars could not account for the quasar's observed a) rapid variability. b) luminosity. c) compact size. d) all of the above.
d) all of the above.
The large Doppler velocity widths of broad emission lines in active galaxies (Seyferts and quasars) could NOT be created by hot emitting clouds that are a) swirling at high velocities around a black hole. b) falling into the neighborhood of a black hole. c) being ejected into a broad cone or disk-shaped wind. d) being ejected along a narrow-angled jet.
d) being ejected along a narrow-angled jet.
The dominant mass component in the Milky Way Galaxy interior to the orbit of the Sun is a) gas and dust contained in giant molecular clouds. b) cosmic ray particles. c) stars. d) dark matter.
d) dark matter.
The best current theories about an isolated black hole suggests that radiation is a) impossible because it is a hole. b) impossible because the escape velocity exceeds the speed of light. c) lower from smaller black holes. d) higher from smaller black holes.
d) higher from smaller black holes.
When a star becomes a red giant it becomes much brighter because it is a) moving closer to us. b) losing its outer envelope. c) fusing iron in its core. d) increasing in size.
d) increasing in size.
As a star first begins to condense from dust and gas clouds, it emits primarily in which wavelength regime? a) X-ray b) ultraviolet c) visual d) infrared e) radio
d) infrared
The most important feature of binary stars is that they enable us to determine stellar a) temperatures. b) pressures. c) compositions. d) masses.
d) masses.
An astrometric binary is known to have an unseen companion whose mass is about equal to the Sun's. The companion is most likely a a) black hole. b) pulsar. c) supergiant. d) white dwarf.
d) white dwarf.
About 25% of the mass of a newborn star is initially in helium. Why doesn't helium also fuse on the main sequence? I. Helium nuclei travel more slowly on average than hydrogen nuclei at any temperature II. Helium nuclei repel each other with more force than do hydrogen nuclei. III. Helium fusion requires three helium nuclei to hit each other almost simultaneously. a) I b) II c) III d) I, II e) II, III f) I, II, III
f) I, II, III
You could best map out the overall spiral structure of our Galaxy by finding a) young open clusters and neutral atomic hydrogen gas. b) evolved stars like planetary nebulae, RR Lyra stars. c) smooth, round globular clusters. d) high velocity stars.
a) young open clusters and neutral atomic hydrogen gas.
Fusion in the core of a main sequence star changes the chemical composition in the core. What happens to the chemical composition outside the core? a) We have no way of finding out. b) The chemical composition outside the core changes very little. c) The same changes occur outside the core as within the core. d) Hydrogen becomes more abundant outside the core.
b) The chemical composition outside the core changes very little.
Quasars are more likely powered by accretion onto a supermassive black hole than by stars because accretion is a) the only natural way to produce radio and X-ray emission. b) a much more efficient means than fusion of extracting energy from matter. c) possible in the early universe before stars even formed. d) responsible for destroying and engulfing stars.
b) a much more efficient means than fusion of extracting energy from matter.
The event that marks the end of a star's evolutionary life before becoming a white dwarf is a) a nova. b) a planetary nebula. c) the exhaustion of hydrogen in the core. d) a helium flash.
b) a planetary nebula.
A star remains at constant size and temperature for a long period of time. Which of the following is most likely to be true? The star generates a) more energy than it radiates into space. b) about as much energy as it radiates. c) less energy than it radiates into space.
b) about as much energy as it radiates.
Most of the hydrogen molecules (two hydrogen atoms bound together) in the universe are found in a) cool stars. b) cold dense interstellar clouds. c) H II regions of ionized hydrogen. d) space between the galaxies
b) cold dense interstellar clouds.
Which property of a star would not change if we could observe it from twice as far away? a) angular size. b) color c) flux d) parallax e) proper motion
b) color
You are an immortal alien being, hiding in the photo archive room of a library on Earth. You can best learn about the life cycles of people by bringing home the drawer filled with photographs of a) individuals. b) crowds on the street. c) people lined up at the voting both. d) doctors.
b) crowds on the street.
If the center of the Sun could be heated slightly, the nuclear reactions would occur faster and hence release more heat, so the Sun's core would a) collapse. b) expand and hence cool back to its previous temperature. c) expand and hence heat up even more. d) explode.
b) expand and hence cool back to its previous temperature.
The helium burning phase for a star of a given mass is much shorter than the hydrogen burning phase primarily because a) the helium mass fraction in the core is less than the hydrogen mass fraction was when the star was young. b) helium releases less energy per reaction than hydrogen. c) the star becomes a white dwarf before it can use most of its helium. d) the temperature never rises high enough for complete helium burning.
b) helium releases less energy per reaction than hydrogen.
A star evolves off the main sequence when a) nuclear reactions begin in the core of the star. b) hydrogen is exhausted in the core of the star. c) hydrogen is exhausted everywhere in the star. d) helium is exhausted in the core of the star.
b) hydrogen is exhausted in the core of the star.
Compared to other types of binaries, a binary star system discovered as a visual binary is likely to have relatively a) high orbital velocities. b) large separation, long period. c) large separation, short period. d) small separation, long period. e) small separation, short period.
b) large separation, long period.
The force of gravity acts to a) make a star larger. b) make a star smaller. c) make a star cooler. d) none of these.
b) make a star smaller.
Stars are formed from cold interstellar gas clouds made up of a) atomic gas of mostly hydrogen, oxygen, carbon and nitrogen. b) molecular hydrogen gas and dust grains. c) some hydrogen gas, comets and asteroids. d) stars are formed from very HOT gas.
b) molecular hydrogen gas and dust grains.
If the large redshifts of quasars were NOT caused by the cosmological expansion, then bright quasars could be explained as a) distant objects that are very luminous. b) nearby luminous objects exploding outward from the Milky Way. c) bright nearby objects severely reddened by intervening dust. d) distant objects severely reddened by intervening dust.
b) nearby luminous objects exploding outward from the Milky Way.
You are asked to determine an accurate distance to the Andromeda Galaxy. Choose the best technique below. a) Doppler shift of spectral lines b) period-luminosity law for Cepheid variable giants in Andromeda c) the Hubble Law of recession of galaxies d) trigonometric parallax using Earth's orbit
b) period-luminosity law for Cepheid variable giants in Andromeda
The initial collapse of the solar nebula may have been initiated by a nearby supernova explosion because a) there is no other known mechanism. b) pre-stellar clouds are normally stable. c) certain odd isotopes are found in the Solar System. d) only 90 percent of atoms in the Solar System are hydrogen. (Note: More than one answer may apply.)
b) pre-stellar clouds are normally stable. c) certain odd isotopes are found in the Solar System.
At high redshift, a larger fraction of galaxies are "active" (show signs of powerful luminous nuclei) than at low redshift. Therefore, we can safely say that a) all galaxies go through an active phase, and more galaxies in the past were active than now. b) some galaxies go through an active phase and more galaxies in the past were active than now. c) all galaxies are either active or normal. d) galaxies may become active more than once in their lifetimes.
b) some galaxies go through an active phase and more galaxies in the past were active than now.
In a color-magnitude diagram of a star cluster, the blue end of the main sequence is useful for defining the age of the cluster because a) blue stars are not affected by extinction and reddening by dust. b) stars just slightly brighter and redder are just now evolving off the main sequence to become giants. c) older, metal-poor stars are blue. d) the hottest stars are the oldest stars in a cluster.
b) stars just slightly brighter and redder are just now evolving off the main sequence to become giants.
The light from the east limb (edge) of the Sun is blueshifted and the light from the west limb is redshifted. This is because a) different kinds of atoms emit light at the opposite edges. b) the Sun is rotating. c) the distance from the Sun to the Earth changes. d) the two sides of the Sun are at different temperatures.
b) the Sun is rotating.
When compared to visual, spectroscopic, or eclipsing binaries, optical doubles are not true binaries because a) they are only binaries in the optical. b) they are not gravitationally bound. c) their radial velocities do not vary. d) they have no proper motions.
b) they are not gravitationally bound.
Isolated black holes slowly evaporate because they slowly leak mass via a) faster-than-light particles that can escape. b) virtual particles that form near the event horizon. c) nuclear fusion near the event horizon. d) holes in the event horizon.
b) virtual particles that form near the event horizon.
Which of the following is impossible to use in estimating distances to other galaxies; why? a) globular clusters; too large and fuzzy b) white dwarfs; too dim c) pulsating variable stars; too variable d) supernovae; don't last long enough
b) white dwarfs; too dim
Which of the following is least easily explainable as a result of interaction between galaxies? a) Some galaxies have long "tails" of stars. b) Rich, regular clusters are dominated by central giant ellipticals. c) Both spiral and elliptical galaxies are seen at very high redshift. d) Some galaxies seems to be undergoing bursts of star formation.
c) Both spiral and elliptical galaxies are seen at very high redshift.
Star A has a radius R and temperature T. At the same distance from Earth, star B has a radius 4R and temperature T/2. Which star appears to be brighter? a) A b) B c) Both stars appear to have the same brightness. d) Cannot tell from information given.
c) Both stars appear to have the same brightness.
A star is burning hydrogen to helium in its core and has ten times the mass of the Sun. Which of the following are true? a) The surface temperature of the star is smaller than that of the Sun. b) The star is redder, more luminous, and larger than the Sun. c) The star is bluer, larger, and more luminous than the Sun. d) both a and b. e) both a and c.
c) The star is bluer, larger, and more luminous than the Sun.
Suppose in a given region of the sky, you see a red star and a blue star. The two are not parts of binary systems, and both stars look pretty typical for their colors. Which of the following is true? a) The red star is older than the blue star. b) The red star is younger than the blue star. c) The stellar ages cannot be determined from the information given.
c) The stellar ages cannot be determined from the information given.
A main sequence star is stable because of self-regulation; a) the nuclear reaction rate does not depend on temperature. b) a slight contraction decreases the nuclear reaction rate. c) a slight contraction leads to higher gas pressure. d) a slight contraction leads to lower internal pressure.
c) a slight contraction leads to higher gas pressure.
One method you could use to search for a high-mass black hole at the center of a galaxy is to look for a) a black dot at the galaxy's nucleus. b) a very high luminosity star. c) a very large range of Doppler shifts around the nucleus. d) distortion in the shapes of stars near the nucleus.
c) a very large range of Doppler shifts around the nucleus.
The photosphere (the visible surface) of the Sun is like a) the surface of the Earth; you could stand on it, if you could survive the heat. b) the surface of the ocean; you couldn't stand on it, but you would clearly be able to detect differences above and below it. c) an apparent surface; you would notice very little change as you go through it, as when you fly through a cloud. d) the surface of a trampoline; you could land on it, but the intense pressure would push you away again.
c) an apparent surface; you would notice very little change as you go through it, as when you fly through a cloud.
If one region of the sky shows nearby stars but no distant stars or galaxies, our view is probably blocked by a) nothing, but directed toward a particularly empty region of space. b) an emission nebula of ionized gas. c) an interstellar gas and dust cloud. d) a concentration of dark matter.
c) an interstellar gas and dust cloud.
A black hole is best defined as a) a star which sucks all matter into itself. b) a window to another universe. c) any object which is smaller than its event horizon. d) the final result of all stellar evolution.
c) any object which is smaller than its event horizon.
Suppose that the period-luminosity law for giant Cepheid variable stars in the Milky Way leaves an uncertainty of 30% in distance estimates made from the measured variability periods of Cepheid stars. Much more distant Cepheids measured in other galaxies will yield distance uncertainties that a) increase with distance. b) are at most 30%. c) are at least 30%. d) depend on the galaxy.
c) are at least 30%.
If the core of the Sun were somehow kept extremely cold for a long time, the Sun would a) freeze into ice. b) expand to about the radius of Earth's orbit. c) collapse to about the size of the Earth. d) collapse to about the size of a large city.
c) collapse to about the size of the Earth.
The temperature in and around the Sun a) drops continuously as you move outward b) rises continuously as you move outward c) drops as you move from the center to the photosphere, then rises above the photosphere d) drops as you move from the center to the photosphere, then rises above the photosphere
c) drops as you move from the center to the photosphere, then rises above the photosphere
Compared to stars like the Sun in the disk of the Milky Way, stars that populate the extended spheroidal halo of the galaxy were born a) earlier, so have had time to accumulate more heavy elements. b) later, so have used up their heavy elements. c) earlier, from more nearly primordial material, so have fewer heavy elements. d) later, so have accumulated more heavy elements from previous generations of stars
c) earlier, from more nearly primordial material, so have fewer heavy elements.
If the rate of hydrogen fusion within the Sun were to increase, the core of the Sun would a) contract and decrease in temperature. b) expand and increase in temperature. c) expand and decrease in temperature. d) stay the same size but increase in temperature.
c) expand and decrease in temperature.
When during a star's evolution its core gets smaller, the rest of the star typically a) also gets smaller. b) stays the same size. c) gets larger. d) explodes in a supernova.
c) gets larger.
If an interstellar cloud contracts to become a star, it is due to which force? a) electromagnetic b) nuclear c) gravitational d) centrifugal
c) gravitational
If a spectroscopic binary is also eclipsing, the maximum Doppler shift in the spectral lines occurs a) each time an eclipse takes place. b) every other time an eclipse takes place. c) halfway between eclipses. d) between eclipses, but the timing depends on inclination
c) halfway between eclipses.
After a star has evolved into a red giant, hydrogen burning a) ceases completely. b) happens only in the center of the star. c) happens only in shells outside the core of the star. d) happens only during novae.
c) happens only in shells outside the core of the star.
After hydrogen fusion stops in the core of a star, the core a) cools and the star as a whole expands. b) cools and the star as a whole contracts. c) heats and the star as a whole expands. d) heats and the star as a whole contracts.
c) heats and the star as a whole expands.
After the Sun's core hydrogen is depleted by nuclear fusion the core will consist primarily of a) carbon. b) deuterium. c) helium. d) oxygen.
c) helium.
You observe two stars at the same distance. One is in the disk of the Milky Way, the other in a direction perpendicularly out of the disk. Chances are that the disk star will be a) less luminous, have a smaller Doppler shift and be reddened by dust. b) more luminous, have a smaller Doppler shift and be reddened by dust. c) more luminous, have a larger Doppler shift and be reddened by dust. d) more luminous, have a smaller Doppler shift and be less reddened by dust.
c) more luminous, have a larger Doppler shift and be reddened by dust.
In general, the orbits of binary stars are a) circular. b) of high eccentricity. c) oriented more or less randomly in space. d) tilted perpendicular to the line of sight.
c) oriented more or less randomly in space.
The word "quasar" comes from "quasi-stellar". What makes quasars quasi-stellar is that they can have a a) proper motion seen between images taken at 2 epochs. b) Doppler velocity shift evident in their spectra. c) point-like appearance in an image. d) binary companion.
c) point-like appearance in an image.
The thickness of our galaxy's disk is determined by the a) circular speed of stars around the galaxy. b) random motion of stars in the plane of the disk. c) random motion of stars perpendicular to the disk. d) the amount of matter in nucleus of the galaxy.
c) random motion of stars perpendicular to the disk.
We know that low mass proto-stars have strong stellar winds because a) they are collapsing in a stable fashion. b) they have thick circumstellar disks. c) the Sun was once a proto-star and has a wind now. d) proto-stars have gas jets that drive massive outflows. (Note: More than one answer may apply.)
c) the Sun was once a proto-star and has a wind now. d) proto-stars have gas jets that drive massive outflows.
The wide variety of spectra observed from different active nuclei of galaxies appear may result from a) how many neutron stars they contain. b) the amount of dust in the Milky Way Galaxy blocking the view. c) the angle at which we view each nucleus. d) whether or not the galaxy has a close companion.
c) the angle at which we view each nucleus.
Giant stars are more rare than main sequence stars because a) they do not form as often as main sequence stars. b) giant stars are unstable. c) the giant stage is very short compared to the main sequence stage. d) elements heavier than helium are relatively rare.
c) the giant stage is very short compared to the main sequence stage.
Two stars are in a binary star system. Star A is 5 solar masses. Star B is 2 solar masses. They are separated by a distance of 200 AU. The period of Star A around the center of mass is _____ the period for Star B around the center of mass. a) larger than b) smaller than c) the same as
c) the same as
Tremendous pressure is created at the Sun's center due to its own gravity. The Sun is kept from collapsing by a) neutrinos and other particles generated by nuclear fusion. b) a hard inner core. c) thermal (gas) pressure generated by nuclear fusion. d) thermal (gas) pressure left over from the formation of the Sun.
c) thermal (gas) pressure generated by nuclear fusion.
The primary reason that massive O-type stars are not found in the galactic halo is because they are a) too massive to be kicked into the halo from the disk. b) so massive that they settle into the thinner disk. c) too short-lived to have persisted from halo formation until today. d) closer to us in the disk than in the extended halo.
c) too short-lived to have persisted from halo formation until today.
Seyferts and quasars are both types of active galaxies, harboring powerful luminous nuclei. Quasar nuclei appear to be more luminous, and therefore their black holes are a) accreting matter at a higher rate. b) more massive. c) less obscured along our sightline. d) Any of the above.
d) Any of the above.
Suppose you measure the parallax of each star in the constellation Taurus (or any other constellation you might choose). Which of the following is the most likely? a) The stars all have the same parallax since we see them together in the same constellation. b) The stars all have nearly the same parallax since they are moving together through space. c) None of them has a measurable parallax since they are mostly within our own Solar System. d) They may have significantly different parallaxes. e) We cannot measure their parallaxes since they are all moving toward our Sun.
d) They may have significantly different parallaxes.
A cold thin cloud of interstellar gas embedded in a hotter, thinner surrounding medium would yield 21-cm radio spectral emission lines of hydrogen showing a) a single broadened emission line. b) broad emission with a narrow spike-like absorption core. c) broad absorption with a narrow spike-like emission core. d) a narrow spike-like emission core and low broad shoulders of emission
d) a narrow spike-like emission core and low broad shoulders of emission
At high redshift, a larger fraction of galaxies are "active" (show signs of powerful luminous nuclei) than at low redshift. If galaxies only become active when they collide or interact with nearby galaxies, then it might be true that a) there were more interactions in the past, and activity fades away. b) the number of distinct galaxies in the universe decreases with time. c) galaxies were closer together in the past. d) all of the above
d) all of the above
Constellations in astronomy are a) physical groupings of genuinely associated stars. b) swarms of planets or asteroids. c) the most accurate way to predict the future. d) arbitrary but useful subdivisions of the sky.
d) arbitrary but useful subdivisions of the sky.
Star clusters are useful to stellar astronomers because the clusters contain stars that a) are all about the same age. b) span a wide range of ages. c) are all at the same stage of stellar evolution. d) are all about the same age and distance.
d) are all about the same age and distance.
The energy of a photon emitted by thermonuclear processes in the core of the Sun takes thousands or even millions of years to emerge from the surface because a) it is circling in the gravitational field of the Sun. b) it loses energy due to convection, conduction, and radiation. c) of the Sun's enormous radius. d) it is absorbed and re-emitted countless times along the way.
d) it is absorbed and re-emitted countless times along the way.
As a one solar mass star evolves into a red giant, its a) surface temperature and luminosity increase. b) surface temperature and luminosity decrease. c) luminosity decreases while the surface temperature increases. d) luminosity increases while the surface temperature decreases.
d) luminosity increases while the surface temperature decreases.
The Tully-Fisher Method of measuring distances to spiral galaxies is based on a relation between the speed of the galaxy's rotation and its absolute luminosity. The existence of the relation suggests that a) distant galaxies are more luminous, with greater velocities. b) rotations of galaxies generate star formation and therefore light. c) luminosity generates rotation. d) luminous galaxies have more stars, and therefore more mass.
d) luminous galaxies have more stars, and therefore more mass.
Inside a star the mass of our Sun, energy is transported from the deep interior out toward the surface by a process most like the process that a) makes a blacktop hot in the summertime. b) heats the coil on an electric stove. c) makes hot water boil. d) makes your hand feel heat when you put it near a candle flame.
d) makes your hand feel heat when you put it near a candle flame.
The disk of stars that forms the major component of the Milky Way Galaxy has its shape due to a) gas pressure from outside the galaxy. b) collapse due to self-gravity. c) rotation alone. d) rotation combined with self-gravity. e) the cosmological expansion of the universe.
d) rotation combined with self-gravity.
For a long-period spatially resolved (visual) binary, the observations that suggest it to be a binary system are the a) velocity curves of the components. b) differing brightnesses (eclipses). c) Doppler velocities of the components. d) small separation and common proper motion.
d) small separation and common proper motion.
Young stars contain heavy elements ("metals") while old stars do not because a) young stars are hotter than old stars. b) young stars are more massive than old stars. c) old stars have used up all their metals in producing energy. d) the gas out of which young stars were formed already contained metals produced by older stars.
d) the gas out of which young stars were formed already contained metals produced by older stars.
The difference in apparent magnitude of the main sequences of stars from two clusters in a colormagnitude diagram tells us a) how much each cluster has evolved. b) if one cluster is "open" and the other is globular. c) the relative ages of the clusters. d) the relative distances of the clusters.
d) the relative distances of the clusters.
The distance to the point-like quasars is found from a) comparing their apparent and absolute magnitude. b) the apparent magnitudes of their supernovae. c) their parallax measured with radio telescopes. d) their redshift and the Hubble Law.
d) their redshift and the Hubble Law.
If we know the distance to an eclipsing binary system, we can determine the member stars' a) temperatures. b) radii. c) masses. d) luminosities. e) All of the above.
e) All of the above.
Which of the following statements are true? a) Stars aren't moving with respect to each other, although if they are nearby then they can appear to move due to parallax. b) Stars like the Sun emit only yellow light, while cooler stars emit only red light. c) Most of the twenty closest stars to the Sun are among the twenty brightest stars in the sky. d) All of the above are true. e) None of the above are true.
e) None of the above are true.
The 11 year solar cycle is NOT followed by the a) number of sunspots on the Sun. b) typical latitude of sunspots on the Sun. c) rate of solar flares. d) incidence of strong aurora on the Earth. e) None of the above.
e) None of the above.
Which of the following can escape from inside the event horizon of a black hole? a) particles of matter b) particles of antimatter c) visible light d) X-rays e) None of the other answers are correct.
e) None of the other answers are correct.
If the temperature in the core of the Sun increased, a) the rate of nuclear reactions in the core would increase. b) the radiation pressure in the core would increase. c) the core of the star would expand. d) the temperature in the core would decrease. e) all of the above
e) all of the above
The material that makes up the Sun was once part of a) the Big Bang. b) another star. c) a molecular cloud. d) a protostar. e) all of the above.
e) all of the above.
Most of the brightest stars in the sky are a) relatively hot main-sequence stars that are relatively close to the Sun. b) relatively cool giant stars that are relatively close to the Sun. c) relatively cool main-sequence stars that are relatively far from the Sun. d) relatively cool main-sequence stars that are relatively close to the Sun. e) giant stars and relatively hot main sequence stars.
e) giant stars and relatively hot main sequence stars.
The mass of our galaxy is best found by a) counting the number of stars in the sky. b) counting the star clusters in the sky. c) counting the hot, massive main sequence stars. d) radio measurements of the amount of interstellar hydrogen. e) measuring the rotation of the Galaxy.
e) measuring the rotation of the Galaxy.
For an eclipsing binary, from just the light curve one can find the a) masses of both stars. b) luminosities of both stars. c) relative masses and diameters of the stars. d) relative masses of the stars. e) relative sizes of the stars.
e) relative sizes of the stars.
Flat-bottomed minima in the light curve of an eclipsing binary imply a) a large temperature difference between the components. b) eccentric orbits. c) partial eclipses. d) tidal distortion. e) total and annular eclipses.
e) total and annular eclipses.
Which of these stars will end its main sequence lifetime most rapidly? a) A very massive star, since more massive stars consume their hydrogen more rapidly. b) A low-mass star, since less massive stars have less hydrogen to burn. c) A star like the Sun, since the combination of fuel-use rate and available fuel amount peaks near 1 solar mass. d) none of the above; all stars have main sequence lifetimes of about 10 billion years.
a) A very massive star, since more massive stars consume their hydrogen more rapidly.
Choose the best evidence that the disk of the Milky Way Galaxy does NOT rotate like a solid wheel. a) Disk stars have Doppler shifts. b) The brightest disk stars form spiral arm shapes. c) Disk stars rotate twice as quickly that are twice as far from the Galactic center. d) The rotation of disk stars around the Sun decreases with distance according to Kepler's laws.
a) Disk stars have Doppler shifts.
What important event occurred while the Sun was in its T Tauri phase (a phase young stars go though in which they have a strong stellar wind similar to the solar wind)? a) Gas and dust remaining in the Solar System were blown away. b) Comets were pushed out of the Solar System. c) The planets formed. d) The Sun shrank to its present size.
a) Gas and dust remaining in the Solar System were blown away.
Suppose that two stars are at equal distance and have the same radius, but one has a temperature that is about twice as great as the other. The flux from the hotter star is a) about 16 times greater. b) about 16 times less. c) about 20 per cent greater. d) about 20 per cent less. e) Not enough information given to answer the question.
a) about 16 times greater.
When making a color-magnitude diagram of a star cluster, we can use apparent brightness instead of intrinsic luminosity because a) all stars in the cluster are at about the same distance. b) all stars in the cluster have about the same age. c) most stars in the cluster are on the main sequence. d) reddening by interstellar dust does not affect clusters. e) the cluster stars have similar chemical compositions.
a) all stars in the cluster are at about the same distance.
In an eclipsing binary, the deeper (more dimmed) eclipse occurs when the ______ star is being eclipsed. a) hotter b) larger c) more luminous d) more massive e) smaller
a) hotter
The energy emitted by the Sun is produced a) in a very small region at the very center of the Sun. b) uniformly throughout the whole Sun. c) throughout the whole Sun, but more in the center than at the surface, as 1/r^2. d) from radioactive elements created in the Big Bang.
a) in a very small region at the very center of the Sun.
The position of the Sun in the Milky Way Galaxy is best described as a) in the disk, slightly more than halfway out from the center. b) very close to the center. c) in an open cluster in the disk. d) in a globular cluster in the halo.
a) in the disk, slightly more than halfway out from the center.
The most effective technique to find distances to other galaxies is to look at objects in the galaxies for which we know the a) luminosity. b) color. c) mass. d) orbital velocity about the center of the galaxy. e) spectral type.
a) luminosity.
Compared to the present day Milky Way Galaxy, the Milky Way of 3 billion years ago would have had a) more gas in the disk. b) more stars in the halo. c) more metal-rich stars. d) no Solar System.
a) more gas in the disk.
The chemical composition of the Sun 3 billion years ago was different from what it is now in that it had a) more hydrogen. b) more helium. c) more nitrogen. d) molecular hydrogen.
a) more hydrogen.
A celestial body growing by accretion of material must surpass a certain mass before hydrogen fusion begins in the core, making it a star. If the strength of the charge on the proton were to be increased, then that minimum mass a) must increase. b) must decrease. c) would not change.
a) must increase.
Rapid variability in the luminous nuclei of quasars is evidence that the emission region must be a) small. b) large. c) moving rapidly. d) exploding.
a) small.
If we see the orbital plane of two distant tightly bound stars nearly edge on, we are most likely to discover the binary system as a a) spectroscopic and eclipsing binary. b) spectroscopic and long-period binary. c) visual and astrometric binary. d) visual and eclipsing binary.
a) spectroscopic and eclipsing binary.
If we observe more distant binary star systems, we are most likely to discover their binarity a) spectroscopically (periodic velocity variation). b) visually (spatially resolved). c) astrometrically (cyclic motion in the plane of the sky). d) by eclipses (periodic photometric variability).
a) spectroscopically (periodic velocity variation).
One model for the formation of the Milky Way can be divided into 2 phases: a spherical gas cloud collapsed to form the stars in the Milky Way's spheroid, then rapidly rotating gas collapsed into a disk-shaped configuration of stars. Since disk stars have higher metallicity, which is most likely? Gas ejected from the a) spheroid stars enriched the material now in the disk stars. b) spheroid stars decreased their metallicity. c) spheroid decreased its angular momentum. d) disk stars puffed out the spheroid stars into a rounder shape.
a) spheroid stars enriched the material now in the disk stars.
The nebulae around T Tauri stars are shaped into disks because of the same process that causes dough to become flat when it is a) spun in the air like pizza dough. b) rolled with a pin like pizza dough. c) squashed between plates like dough for a burrito. d) baked on a flat sheet like a cookie.
a) spun in the air like pizza dough.
Considering a representative sample of 100 star systems in our Galaxy, a) stars in binary systems would be more common than single stars. b) about half of the stars would be in resolved visual binaries. c) about half of the stars would be eclipsing binaries. d) most would be single stars
a) stars in binary systems would be more common than single stars.
The solar corona has temperatures roughly the same as temperatures in the Sun's core, where nuclear fusion takes place. Fusion doesn't occur in the corona because a) the density in the corona is too low. b) the corona has too many free electrons. c) atoms in the corona are mostly ionized. d) the corona has more heavy atoms than the core. e) Two of the above.
a) the density in the corona is too low.
If you find a cluster of very old stars, you would expect the cluster to appear a) very concentrated toward its center. b) very spread out. c) shaped like a disk. d) bipolar in shape, like a barbell.
a) very concentrated toward its center.
If we observe the orbit of a binary star system face-on, it is most likely to be detected as a binary a) visually (separation in the plane of the sky). b) spectroscopically (periodic velocity variation). c) astrometrically (cyclic motion in the plane of the sky). d) by eclipses (periodic photometric variability).
a) visually (separation in the plane of the sky).
The nuclei of most spiral galaxies appear redder than their spiral arms because of a) young blue stars in the arms, and old red ones in the nuclei. b) emission nebulae and dust in the nuclei. c) receding nuclei and advancing spiral arms (Doppler shifts). d) nuclear reactions.
a) young blue stars in the arms, and old red ones in the nuclei.