Astronomy Exam 2

D) after a white dwarf cools off it becomes too cold and dark to emit visible light

A charming friend of yours who has been reading a little bit about astronomy accompanies you to the campus observatory and asks to see the kind of star that our Sun will ultimately become, long, long after it has turned into a white dwarf. Why is the astronomer on duty going to have a bit of a problem satisfying her request? A) the universe is not even old enough to have produced any white dwarfs yet B) all the old stars in our Galaxy are located in globular clusters and all of these are too far away to be seen with the kind of telescope a college or university campus would have C) after being a white dwarf, the Sun will explode, and there will be nothing left to see D) after a white dwarf cools off it becomes too cold and dark to emit visible light E) astronomers only let people with PhD's look at these stellar corpses; it's like an initiation rite for those who become astronomers

A) a star of about the same mass as our Sun

A group of graduate students, bored during a cloudy night at the observatory, begin to make bets about the time different stars will take to evolve. If they have a cluster of stars which were all born at roughly the same time, and want to know which star will become a red giant first, which of the following stars should they bet on? A) a star of about the same mass as our Sun B) a star that would type O on the main sequence star C) a star of about 1/2 the mass of our Sun D) a star of about 8% the mass of our Sun E) you can't fool me, all stars reach the red giant stage in roughly the same number of years

B) neutron star

After a supernova event, the remaining core of the star may become a... A) planet B) neutron star C) white dwarf D) black dwarf

B) a singularity

Deep inside a black hole (and hidden from our view) is the compressed center, where all the "stuff" of the star goes. Astronomer call this central point A) a black dwarf B) a singularity C) a time-stopping point D) an event horizon

C) a distortion in spacetime caused by the gravity of the Sun

Einstein suggested that the regular change (advance) in the perihelion of the planet Mercury could be explained by: A) the presence of a planet inside the orbit of Mercury, whose gravity influenced Mercury B) the pull of a small black hole that orbits our Sun so closely that we are not able to see it C) a distortion in spacetime caused by the gravity of the Sun D) a distortion in our view of the solar system caused by the Earth's atmosphere E) the presence of a strong magnetic field in the Sun, which causes huge outburst of material

A) a supernova explosion

Elements heavier than iron can be created during: A) a supernova explosion B) the big bang C) the red giant stage in a star's life D) the main sequence E) astronomers don't have any idea of where these elements came from; it's an unsolved mystery

D) neutrino

In a collapsing star of high mass, when electrons and protons are squeezed together with enormous force, they turn into a neutron and a: A) nucleus of iron B) positron C) radio wave D) neutrino E) helium nucleus

D) a few tenths of a second

In a supernova like SN1987A, once the crisis of iron fusion has begun, roughly how long does it take the star's core to collapse? A) 10 thousand years B) 10 million years C) one year D) a few tenths of a second E) a hundred years

B) False

Perfect linear alignment of a background source, lens, and observer will yield an Einstein cross. A) True B) False

C) the event horizon

The region around a black hole where everything is trapped, and nothing can get out to interact with the rest of the universe, is called A) the singularity B) the gravitational redshift zone C) the event horizon D) the neutron star radius

C) 3 solar masses

What is the lower limit for the mass of a black hole? A) 10 solar masses B) 2 solar masses C) 3 solar masses D) 30 solar masses

C) radio

What kind of telescope did Jocelyn Bell use to discover pulsars in 1968? A) x-ray B) ultraviolet C) radio D) neutrino E) visible light

C) toward the upper right

When the outer layers of a star like the Sun expand, and it becomes a giant, which way does it move on the H-R diagram? A) toward the upper left B) it moves horizontally, but stays on the main sequence toward the lower left C) toward the upper right D) toward the lower right

A) red giant

Which of the following is the largest (in diameter)? A) red giant B) neutron star C) white dwarf D) main sequence star

C) because they just cannot get hot enough for the fusion of heavier nuclei

Why can a star with a mass like our Sun not fuse (produce) further elements beyond carbon and oxygen? A) because all such elements become radioactive and their nuclei break apart rather quickly B) because there are no elements heavier than those two; they are the heaviest nuclei in nature because all such stars explode before they can make any other elements C) because they just cannot get hot enough for the fusion of heavier nuclei D) because the cores of such stars get too hot for further types of fusion to be able to happen

C) he should travel to a black hole, and spend some time in orbit just above the event horizon

A handsome, rich, but vain movie star notices that he is starting to age, and consults you as his astronomy expert, to see if you can find an astronomical way to slow down his aging. Which of the following strategies would IN THEORY allow him to age more slowly than the rest of humanity. A) he should be in orbit around the Earth, and expose himself to as many cosmic rays as possible B) he should live far away from the gravity of any planet or star (in a deep-space station) C) he should travel to a black hole, and spend some time in orbit just above the event horizon D) he should always live at sea level on Earth, and never go to any mountains or high altitudes E) he should live in a room filled with positive electrical charge

D) a neutron star

A member of the college football team wants to weigh as much as possible. Assuming he could somehow survive on all of them, at the surface of which object would he weigh the most? tip: Your "weight" is dependent on gravity. The force due to gravity is dependent on the mass of the celestial body you're on. For example, we "weigh" less on the moon than we do here on Earth because the moon has less mass and less gravity. Our mass stays the same. So how do the masses (or gravity) of the celestial bodies below compare? A) an M-type star in the main sequence stage of its life B) an O-type star in the main sequence stage of its life C) you can't fool me, his weight would be the same on all of the above objects D) a neutron star E) a white dwarf

C) in a globular cluster

A science fiction writer needs an environment for her latest story where stars are as crowded together as possible. Which of the following would be a good place to locate her story? A) in a stellar association B) in a small open cluster C) in a globular cluster D) in the outer regions of a spiral galaxy's disk

A) infrared

A star with a mass like the Sun which will soon die is observed to be surrounded by a large amount of dust and gas -- all material it has expelled in the late stages of its life. If astronomers want to observe the radiation from such a giant star surrounded by its own debris, which of the following bands of the spectrum would be the best to use to observe it? A) infrared B) very long wavelength radio waves C) ultraviolet D) gamma-rays E) x-rays

A) a globular star cluster

A type of star cluster that contains mostly very old stars is A) a globular star cluster B) a galaxy C) a stellar association D) an HII region E) an open cluster

E) smaller in diameter

A white dwarf, compared to a main sequence star with the same mass, would always be: A) more massive B) younger in age C) the same size D) redder in color E) smaller in diameter

C) the slower time runs near it

According to Einstein's general theory of relativity, the stronger a star's gravity, A) the less space-time around it will be distorted B) the smaller the event horizon will be of the black hole it makes C) the slower time runs near it D) the weaker its pull on another star will be E) the weaker the x-rays we see from it

A) causes a curvature (or warping) of spacetime

According to the general theory of relativity, the presence of mass A) causes a curvature (or warping) of spacetime B) is equivalent to the presence of light C) causes curved paths to straighten out until they are exactly straight lines D) causes motion at the speed of light squared E) will cause a black hole to form, unless there is motion

E) none of these

After it experiences a "helium flash" a star like the Sun will have a brief period of stability, fusing helium into carbon (and sometimes oxygen). During this brief stable stage, the star A) gets to be even larger in diameter than it was as a red giant B) returns to the position on the H-R diagram that the star had in its main-sequence stage C) increases tremendously in luminosity D) is able to fuse many of the heaviest elements (such as iron and gold) in its superhot core E) none of these

A) explodes outward as a supernova

After the core of a massive star becomes a neutron star, the rest of the star's material A) explodes outward as a supernova B) is vaporized by the incredible heat of the dying star and evaporates C) falls inward very slowly, taking billions of years to get really compressed D) makes a planetary nebula, which gently moves outward from the center E) continues regular fusion and returns to the main sequence

C) plot an H-R diagram for the stars in the cluster

An astronomy student, for her PhD, really needs to estimate the age of a cluster of stars. Which of the following would be part of the process she would follow? A) search for planets like Jupiter around the stars in the center of the cluster B) search for x-rays coming from the center of the cluster C) plot an H-R diagram for the stars in the cluster D) measure the Doppler shift of a number of the stars in the cluster E) count the number of M type stars in the cluster

C) the O and B type stars

As a cluster of stars begins to age, which type of star in the cluster will move off the main sequence of the H-R diagram first? A) G type stars, like our Sun B) the lowest mass stars, which have the least amount of fuel for fusion C) the O and B type stars D) M type stars, which are the coolest E) all the stars in a cluster are born at the same time; so they will all move off the main sequence at the same time, as they evolve

B) from the fusion of hydrogen into helium in a shell around the core

As a star becomes a giant, its outer layers are expanding. Where does the energy for expanding these layers come from? A) from the fusion of helium into carbon in the core from the long-term fusion of hydrogen into helium in the core B) from the fusion of hydrogen into helium in a shell around the core C) from a magnetic dynamo effect in the star's outer layers, caused by a much stronger magnetic field inside the star D) from an explosion in the core

B) appear to get closer and closer to the Schwarzschild radius, but never arrive there.

Astronauts falling into a black hole would not notice anything special happening as they fell through the Schwarzschild radius. Watching from the outside, we would see the astronauts A) age very rapidly and disappear. B) appear to get closer and closer to the Schwarzschild radius, but never arrive there. C) bounce off the Schwarzschild radius. D) pass right through the black hole and out the other side. E) disappear from sight as they crossed the Schwarzschild radius.

A) rotating neutron stars

Astronomer have concluded that pulsars are rotating black holes A) rotating neutron stars B) rotating red giants C) protostars that are collapsing and spinning very rapidly D) supernovae that are about to explode

C) the cosmic rays produced by supernova explosions would have contributed to the rate of mutations over many generations

Astronomers believe that the many supernova explosions that happened in the Milky Way Galaxy could have played a role in the evolution of life over billions of years. How would they have influenced the development of life on Earth? A) supernova explosions would have ripped continents from the crust, and caused plate tectonics B) supernova explosions probably killed off many animal species on Earth with their dangerous radiation, leaving the planet for humans to dominate C) the cosmic rays produced by supernova explosions would have contributed to the rate of mutations over many generations D) supernova explosions would have destroyed most of the planets in the Galaxy, tearing them apart, leaving the only the Earth to give rise to life E) actually, astronomers know that supernova explosions can only affect the star system in which they happen; they have no effect on the rest of the Galaxy

A) Such fast-spinning pulsars have companion stars near them, which dump material on the pulsar and that spins it faster and faster

Astronomers have discovered pulsars spinning 500 x per second or more. How do astronomers think pulsars got to be spinning so outrageously fast? A) Such fast-spinning pulsars have companion stars near them, which dump material on the pulsar and that spins it faster and faster B) Such pulsars were thrown out of their original location because the supernova explosion that produced them was not the same energy in all directions; this being pushed to one side made them spin faster C) Astronomers have no suggestion for why such fast-spinning pulsars exist D) Because the neutron stars that are the pulsars were small when they were born, all pulsars should be spinning this fast or faster E) Pulsars are planets very close to their stars, and they have to spin so fast so they don't fall in

D) from the Doppler shift in the line radiation from the nebula

Astronomers have noticed that the visible filaments in the Crab Nebula are moving toward us at great speed. How can they know about motions like this? A) from the spacing of the pulsar pulses B) from the width of the pulsar pulses C) from the color of the nebula's continuous radiation from the H-R diagram D) from the Doppler shift in the line radiation from the nebula

C) some stars can lose a lot of mass on their way to becoming white dwarfs; thus the white dwarfs could have started out as quite massive stars

Astronomers observe a young cluster of stars, where stars with three times the mass of the Sun are still on the main sequence of the H-R diagram. Yet the cluster contains two white dwarfs, each with a mass less than 1.4 times the mass of the Sun. If we can show that the white dwarfs are definitely part of the cluster, how can their presence so soon in the life of the cluster be explained? A) the lower the mass of a star, the more quickly it goes through each stage of its life B) white dwarfs are what is left over after a star explodes and throws off 90% of its mass C) some stars can lose a lot of mass on their way to becoming white dwarfs; thus the white dwarfs could have started out as quite massive stars D) stars less massive than 1.4 times the mass of the Sun go through the white dwarf stage in their lives before they become main sequence stars E) astronomers can think of no way to explain this problem; it has them completely baffled

C) because white dwarfs get really hot, we can search for their ultraviolet radiation

Because white dwarfs are small, as their name implies, they are hard to see. What is a way astronomers have to find white dwarfs that distinguishes them from main sequence stars? A) there is no way to distinguish white dwarfs from other dim stars. That's why we only know two or three white dwarfs in the sky. B) all white dwarfs pulsate (they get brighter and dimmer) every few minutes and this regular change in brightness is easy to notice C) because white dwarfs get really hot, we can search for their ultraviolet radiation D) because white dwarfs are making complex molecules in their outer regions, we can search for them with radio telescopes E) because white dwarfs all have planets around them, we can use the transit method to find them

A) gravity; pressure

Black holes form when ___________________overcomes the outward________________produced by nuclear reactions within a star. A) gravity; pressure B) pressure; energy C) energy; pressure D) gravity; energy

A) search for flickering x-rays being given off from an accretion disk around the black hole, as it "eats" part of a neighbor star

Far away from a black hole (at the distance of another star), which of the following is a possible way to detect it? A) search for flickering x-rays being given off from an accretion disk around the black hole, as it "eats" part of a neighbor star B) you can't fool me, you can never, ever detect a black hole! C) look for the pulsed radio waves it gives off as it rotates like a lighthouse D) notice what a large amount of star light it blocks from behind it E) look for the neutrinos that escape from the event horizon

C) infinite density

General Relativity predicts that black holes have A) infinite volume B) infinite mass C) infinite density

C) mostly in a large spherical halo (or cloud) surrounding the flat disk of the Galaxy

How are globular clusters distributed in our Milky Way Galaxy? A) where the giant molecular clouds are found B) only in the very center of the Galaxy, really crowded together completely randomly: you never know where we will find one C) mostly in a large spherical halo (or cloud) surrounding the flat disk of the Galaxy D) only in the main spiral disk of the galaxy

C) its mass

How long a main sequence star remains on the main sequence in the H-R diagram depends most strongly on A) its initial composition B) its radial velocity (as measured from the spectrum) the number of companion stars or planets orbiting it C) its mass D) its ability to fuse the element carbon into some other element

B) x-ray

If gas approaches a black hole, it will often heat up and emit ________________ that can be detected telescopically. A) radio B) x-ray C) purple light D) white light

D) planetary nebulae expand rapidly and soon become too faint to be visible

If most stars are low-mass stars, and low-mass stars typically eject a planetary nebula, why then do astronomers see relatively few planetary nebulae in the sky? A) planetary nebulae can only be detected through their faint radio emissions planetary nebulae quickly fall back onto the star produced them B) planetary nebulae are only visible when a planet surrounding the star plows through the ejected material, causing it to glow C) while most stars are low-mass when they are born, throughout their lives they gather more and more material; so few stars are low-mass when they die D) planetary nebulae expand rapidly and soon become too faint to be visible

A) the disk of our Galaxy contains a great deal of dust, which tends to block the light of supernova explosions from more distant parts of our Galaxy

If observations of supernovae in other galaxies show that such an explosion happens in a spiral galaxy like the Milky Way on average every 25 to 100 years, why have astronomers on Earth not seen a supernova explosion in our Galaxy since 1604? A) the disk of our Galaxy contains a great deal of dust, which tends to block the light of supernova explosions from more distant parts of our Galaxy B) most supernova explosions produce only high-energy gamma-rays and very little light actually, there have been supernova explosions observed, but there is a government conspiracy to keep ordinary citizens from learning about them (just like the alien creatures that were in Roswell, New Mexico and Area 51) C) all the explosions happened in that part of the sky which is only visible from the Earth's southern hemisphere, and we do not have any large telescopes down there D) we have been very unlucky; there have been far fewer explosions than average recently

C) heavier elements are made in the cores of significantly more massive stars than the Sun, which can get hotter in the middle

If stars with masses like our Sun's cannot make elements heavier than oxygen, where are heavier elements like silicon produced in the universe? A) heavier elements are made in the proto-planetary disks that accompany many newly forming stars B) heavier elements are made in the cores of planets that are molten and hot when they form C) heavier elements are made in the cores of significantly more massive stars than the Sun, which can get hotter in the middle D) this is an unsolved problem in astronomy; no one knows E) these heavier elements were made in the Big Bang at the time the universe began, and have been part of the universe ever since

B) False

If the Sun were to be spontaneously replaced by a blackhole of the same mass, the Earth would get sucked in. A) True B) False

B) the first generation stars contain little or no elements heavier than helium

If we look back to the first generation of stars made when the Galaxy was first forming, how do they differ from stars being formed today? A) You Answered I disagree; I think first generation stars will be like stars forming today in all ways B) the first generation stars contain little or no elements heavier than helium C) the first generation stars all live their lives much more slowly than stars today (so they last a long time) D) the first generation stars never become red giants E) the first generation stars cannot form planets of any kind

D) it was fused from 3 helium nuclei in the core of a red giant star long before the Sun existed

If you trace back the history of a carbon atom in your little finger through all of cosmic history, where did this atom most likely originate? A) it was made in the big bang B) it was fused from hydrogen atoms during the main-sequence stage of a star's life long before the Sun existed C) it was made from smaller nuclei in the hot core of the Earth when our planet first formed D) it was fused from 3 helium nuclei in the core of a red giant star long before the Sun existed

A) open clusters

If you wanted to discover the youngest stars you could find in some grouping of stars in the Galaxy, which type of star group would be the best to search? A) open clusters B) globular clusters C) stellar associations D) the type of clusters that form a halo around the disk of the Milky Way E) all types of star groups have an equal number of young stars in them

A) ultraviolet radiation from the collapsing hot star at the center

In a planetary nebula, the shell of expelled material is glowing intensely. What is the main source of energy for this glow? A) ultraviolet radiation from the collapsing hot star at the center B) the change of electrons and protons into neutrons the fusion of hydrogen into helium in the nebula C) the explosion of the dying star friction, as the atoms of the expelled shell rub against each other

A) run out of fuel

In order for a massive star to form a black hole, it must first ________________. A) run out of fuel B) begin rotating C) expand D) emit x-rays

A) the message will never emerge from the event horizon

In the far future, a starship becomes trapped inside the event horizon of a black hole. Although the crew discovers that their ship cannot out, they at least want to send a message to other ships in the area to stay away from the danger zone. If they send out a message in the form of a radio wave, what will be its fate? A) the message will never emerge from the event horizon B) the radio wave will only emerge from the event horizon if it is moving in the direction of the magnetic north and south pole of the star that formed the black hole C) the radio wave will become a gamma ray by the time it emerges from the event horizon D) although the radio wave will emerge from the event horizon, all the information in the message will be garbled

A) because neutron star beams come out of the north and south poles of a magnetic field

In the model that astronomers have developed for pulsars, why do they suggest that there must be two beams of energy coming from the pulsar? A) because neutron star beams come out of the north and south poles of a magnetic field B) this is an unsolved mystery in astronomy; no one has any good suggestions C) because pulsars represent supernova explosions that come out in opposite directions (but not every direction) when a massive star dies D) because pulsars always come in pairs E) because neutron stars are always surrounded by two moons (satellite bodies)

D) the shell let go by a dying low-mass star

Many names used by astronomers are misleading or outdated. A good example is the term planetary nebula,which astronomers use to refer to: A) a region of gas and dust where new planets have recently formed B) a globular cluster, which looks like a planet through very small telescopes C) a solar system in formation D) the shell let go by a dying low-mass star E) the remains of an exploded high-mass star

B) the point on the main sequence where stars begin to "turn off" -- to move toward the red giant region

On an H-R diagram of a cluster of stars, which characteristic of the diagram do astronomers use as a good indicator of the cluster's age? A) the lowest luminosity star that is visible in the cluster B) the point on the main sequence where stars begin to "turn off" -- to move toward the red giant region C) how high up on the main sequence M type stars are found D) the number of M stars on the main sequence E) the coolest surface temperature for a star that they can measure

A) the mass inside the event horizon

Once a black hole forms, the size of its event horizon is determined only by A) the mass inside the event horizon B) the size (diameter) of the star that collapsed into the black hole C) the time since the black hole formed D) you can't fool me; every black hole has an event horizon of the same size E) the composition of the material that formed the black hole

A) of distortions in spacetime

Pulsars "wobble" in their orbit because A) of distortions in spacetime B) they are losing energy C) it's an optical illusion D) something knocked them off balance

A) can fuse elements beyond carbon and oxygen in their hot central regions

Really massive stars differ from stars with masses like the Sun in that they A) can fuse elements beyond carbon and oxygen in their hot central regions B) go through all the stages of their lives more slowly do not really go through a main sequence stage in their lives C) are no longer forming in the Galaxy; they only formed very early in the Galaxy's history D) they are significantly less luminous after the main sequence stage is over

E) an entire galaxy of stars (with about a billion stars in it)

Suppose each of the following objects could collapse into a black hole. Each black hole would have a sphere around it that is the limit for escape -- once you are inside this region, you cannot get away. For which object would this region be the largest in diameter? A) a star with the mass of our Sun B) a planet like Jupiter C) an entire cluster of stars (with about 150 stars in it) D) a star that was type O when it was on the main sequence E) an entire galaxy of stars (with about a billion stars in it)

D) X-ray objects

Suspected black holes are detected as _____ in a binary observed singularities A) Black holes cannot be detected by any known means. B) novae C) dark objects D) X-ray objects

C) S. Chandrasekhar

The astrophysicist who first calculated the highest mass that a dying star can have and still be a white dwarf was A) A. Hewish B) D. Generate C) S. Chandrasekhar D) H. R. Russell E) I. Shelton

E) almost all the hydrogen in its core that was hot enough for fusion has been turned into helium

The event in the life of a star that begins its expansion into a giant is A) it reaches the stage that astronomers call the zero-age main sequence B) the star's internal structure reaches equilibrium for the first time in its life C) the core reaches a temperature of ten million degrees D) as much as 90% of the star explodes violently E) almost all the hydrogen in its core that was hot enough for fusion has been turned into helium

A) globular clusters

The oldest structures in our Galaxy turn out to be A) globular clusters B) HII regions C) giant molecular clouds D) stellar associations E) open clusters

C) mass

To predict whether a star will ultimately become a black hole, what is the key property of the star we should look at? A) surface temperature B) color C) mass D) diameter E) distance

C) more slowly

Wearing a very accurate watch, you volunteer to go on a mission to a black hole in a spaceship that has powerful rockets. You are able to orbit the black hole and stay a little distance outside of the event horizon. Compared to watches on Earth, your watch near the black hole will run: A) more quickly B) you can't fool me, watches near a black hole don't change the pace at which they run C) more slowly

B) gravitational waves are much weaker than e-m waves, and therefore require very, very precise equipment to detect

What is a key reason that gravitational waves are so much harder to detect than electro-magnetic (e-m) waves? A) gravitational waves get all mixed up with sound waves in the Earth's atmosphere, and are therefore hard to distinguish from all the sound B) gravitational waves are much weaker than e-m waves, and therefore require very, very precise equipment to detect C) gravitational waves don't create any kind of disturbance the way e-m waves do D) gravitational waves are so strong, they really shake our detectors, making measurements difficult E) you can't fool me; gravitational waves are much easier to detect than e-m waves

A) an O-type star

What type of main sequence star is most likely to become a black hole? A) an O-type star B) a G-type star C) an M-type star D) a K-type star E) you can't fool me, all spectral types on the main sequence have an equal chance of becoming black holes

A) white dwarf

When a single star with a mass equal to the Sun dies, it will become a A) white dwarf B) black hole C) burster D) pulsar E) neutron star

C) the core is collapsing under its own weight and heating up from the compression; this heats the next layer up

When a star first begins the long path toward becoming a red giant, a layer of hydrogen around the core begins to undergo fusion. If this layer was too cold to do fusion throughout the main sequence stage, why is it suddenly warm enough? A) as the star expands, all the layers heat up B) the heat comes from the fusion of carbon in the core, which starts right away the heat comes from the outer layers of the star, which are much hotter than the core C) the core is collapsing under its own weight and heating up from the compression; this heats the next layer up D) this is an unsolved problem in astronomy, but something must be heating that layer, since we observe red giants out there

B) we found strongly magnetic neutron stars whose whirling beams of energy were detected as pulsars

When neutron stars were first predicted theoretically, no scientist expected to be able to detect one of them across interstellar distances. What enabled astronomers to find neutron stars in the late 1960's? A) they give off a lot more light than expected, and can be seen glowing with a reddish light from far away B) we found strongly magnetic neutron stars whose whirling beams of energy were detected as pulsars C) they are so large, their dark outline block a significant amount of starlight from behind them astronomers have actually only found one neutron star and that was discovered very close to us and by sheer luck D) some neutron stars soon collapse to be white dwarfs, whose light can be detected further away

B) from a disk of material around the black hole (material that has been pulled from the companion star and is falling toward the black hole)

When one member of a binary star system is a black hole, and astronomers detect flickering x-rays coming from the system, where are these x-rays usually coming from? A) from a distant galaxy that just happens to lie behind the black hole system (astronomers discovered that such x-rays have nothing to do with the black hole) B) from a disk of material around the black hole (material that has been pulled from the companion star and is falling toward the black hole) C) from inside the black hole event horizon from the singularity D) from the photosphere of the companion star (the star that is not a black hole)

D) their mass grows significantly as they incorporate planets and interstellar matter near the star

When stars become giants, which of the following does NOT usually happen? A) their surface temperatures become lower than before B) they lose a significant amount of mass from their outside layers C) their overall luminosities increase D) their mass grows significantly as they incorporate planets and interstellar matter near the star E) their outer envelopes expand significantly

E) a neutron star

When the mass of a star's core is greater than 1.4 times the mass of the Sun, degenerate electrons can't keep it stable as a white dwarf. Instead, it becomes: A) a planetary nebula B) a red giant C) a black dwarf D) a ball of solid iron, with layers of other elements around it E) a neutron star

A) the clock on the ground floor ran a tiny bit slower

When two identical atomic clocks, one on the ground floor and one on the top floor, are compared, A) the clock on the ground floor ran a tiny bit slower B) the clocks ran at exactly the same pace in both locations C) the clock on the top floor ran a tiny bit slower

A) white dwarfs, neutron stars, black holes

Which are listed in the order of their increasing density? A) white dwarfs, neutron stars, black holes B) black holes, white dwarfs, neutron stars C) neutron stars, black holes, white dwarfs D) black holes, neutron stars, white dwarfs

A) red giant, sun, white dwarf, neutron star, black hole

Which choice has the objects ranked by size (radius), largest to smallest? (here, consider the singularity to be the size of a blackhole. The Schwarzchild radius describes the gravitational effect) A) red giant, sun, white dwarf, neutron star, black hole B) black hole, red giant, sun, neutron star, white dwarf C) sun, red giant, black hole, neutron star D) red giant, white dwarf, sun, neutron star, black hole

C) The one at the bottom of that same mountain.

Which clock ticks more slowly? A) Cannot be determined from the information given. B) They tick at the same rate. C) The one at the bottom of that same mountain. D) The one on the top of a mountain.

C) Time is observed to run more slowly in clocks when they are flown to high altitudes above the Earth.

Which of the following is NOT a proof of the theory of General Relativity? A) The path of light from distant stars is bent by the Sun's gravitational field. B) The two stars in a binary system each orbit about the center of mass of the system. C) Time is observed to run more slowly in clocks when they are flown to high altitudes above the Earth. D) The precession of Mercury's orbit is more rapid than is predicted by Newton's laws.

E) the neutron star is disrupted and tears apart into many pieces

Which of the following is NOT a result of supernova explosions? A) a tremendous flood of high-energy cosmic ray particles is released B) any planets within a few dozen LY of the explosion are bathed with life-threatening radiation C) new heavier elements (including such heavy nuclei lead and uranium) are fused by neutron bombardment during the explosion D) many of the elements the star fused during its life are blasted out into space E) the neutron star is disrupted and tears apart into many pieces

D) the electrons get as close to each other as possible and resist further compression

Which of the following is a characteristic of degenerate matter in a white dwarf star? A) helium is actively fusing into carbon B) the atoms drink, smoke, use bad language, and are attracted to the wrong kinds of particles C) electrons and protons join together in the nucleus to make neutrons and neutrinos D) the electrons get as close to each other as possible and resist further compression E) the degenerate matter region is expanding as time passes, until it covers a region the size of the orbit of Mars

C) the pulsar beam doesn't happen to point toward us in many cases

Which of the following is one reason we do not detect a pulsar in many remnants of supernova explosions? (Careful! This one is tricky!) A) many supernova remnants contain white dwarfs or black dwarfs B) most stars (our own Sun, for example) don't rotate at all, so no pulsar can form C) the pulsar beam doesn't happen to point toward us in many cases D) the radiation with which we detect pulsars doesn't get through the Earth's atmosphere

A) white dwarf

Which of the following stages can only occur in the life of a low-mass star (whose final mass is less than 1.4 times the mass of the Sun)? A) white dwarf B) supernova C) main-sequence D) proto-star E) red giant

A) all of these

Which of the following stages will our own Sun go through in the future: A) all of these B) eventually fusing helium into carbon C) spending a long time on the main sequence D) expanding to become red giant E) giving off a planetary nebula

E) all of these choices

Which of the following stages will the Sun definitely go through as it gets older? A) red giant B) black dwarf C) white dwarf D) source of a planetary nebula E) all of these choices

A) inside, there are a number of newly formed massive stars (O and B type stars)

Which of the following statements about the Crab Nebula is FALSE? A) inside, there are a number of newly formed massive stars (O and B type stars) B) it is the remnant of a supernova explosion first seen on Earth in 1054 AD C) the nebula still puts out more energy (at all wavelengths) than 100,000 Suns D) the neutron star inside shows clear evidence of slowing down just a little bit in its rotation E) we can detect a pulsar inside the nebula using both radio waves and visible light

A) as the star is dying, a considerable part of its mass will be lost into space

Which of the following statements about the life of a star with a mass like the Sun is correct? A) as the star is dying, a considerable part of its mass will be lost into space B) after the main sequence stage, there is no further fusion of hydrogen anywhere in the star before the star dies, it will fuse dozens of elements in its core C) at the end of its life, the star will explode as a supernova D) the core of this star will be too massive to form a white dwarf

C) main sequence stars are rare in the Galaxy, so we are lucky to be living around one

Which of the following statements about the main sequence stage in the life of a star is FALSE? A) different stars spend a different amounts of time (number of years) in the main sequence stage, depending on the characteristics they were born with B) all stars spend the majority of their lives in the main sequence stage C) main sequence stars are rare in the Galaxy, so we are lucky to be living around one D) during the main sequence stage, energy to power the star is provided by the fusion of hydrogen during the main sequence stage, the mass of any star does not change significantly

C) The Sun will lose a significant amount of mass during and after its red giant phase

Which of the following statements about the mass of the Sun during its lifetime is correct? A) The only way the Sun loses mass is by turning a bit of mass into energy during fusion, and this loss is very small B) It will have the same exact mass from birth to death C) The Sun will lose a significant amount of mass during and after its red giant phase D) The Sun will lose almost ALL of its mass before it dies; the remaining mass will be less than the mass of Jupiter E) The Sun will lose some mass during the late periods of its life, but the amount loss will be less than 1 %.

A) the white dwarf mass will curve spacetime; light has to follow that curvature

Which of the following statements about the way the mass of a white dwarf affects spacetime is correct? A) the white dwarf mass will curve spacetime; light has to follow that curvature B) since no experiments have ever tested Einstein's theory of general relativity, it is impossible to say what will happen C) the white dwarf mass will not affect spacetime at all; only black holes affect spacetime the white dwarf mass will attract light, and pull it in a curved path; spacetime is not affected D) the white dwarf mass will have enough gravity to straighten out any curvature in spacetime; so spacetime near the white dwarf will be flat

E) K

Which of the following types of stars will spend the longest time (the greatest number of years) on the main sequence? A) O B) A C) you can't fool me; every star spends about the same number of years on the main sequence D) G E) K

B) because the fuel for energy production in this stage of the star's life is hydrogen; and that is an element every star has lots and lots of

Why do all stars spend most of their lives on the main sequence? A) because during this stage the star contracts from enormous size to a relatively small ball; this takes a long time B) because the fuel for energy production in this stage of the star's life is hydrogen; and that is an element every star has lots and lots of because in this stage, the processes inside the star do not generate any energy; thus the star can continue in this stage indefinitely C) because the neutrinos created inside the Sun do not carry any energy away with them D) this is an unsolved problem in astronomy, and is an important project for the world's largest telescopes to work on

C) red giants are so big, the gravity at their surface (that holds material to the star) is less

Why is it easier for red giants to lose mass than main sequence stars? A) red giants are made of carbon and oxygen throughout, which escape more easily B) all red giants explode at the end of their lives red giants are much hotter on their surfaces, allowing gases to move away C) red giants are so big, the gravity at their surface (that holds material to the star) is less D) you can't fool me, stars lose the same amount of mass during every stage of their lives

C) they were built up from smaller nuclei during a supernova explosion

Your sweetheart gives you a piece of gold jewelry as a present to celebrate your passing your astronomy class. Where did the gold atoms in that gift originally come from (where were they most likely made)? A) they were fused during the main sequence stage of a low-mass star B) they were fused deep inside the hot core of the Earth a few million years ago C) they were built up from smaller nuclei during a supernova explosion D) they were produced from other atoms in the cool outer envelopes of a red giant star E) they were fused during the supergiant stage in the life of a massive star