WQ #24

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. an event horizon b. a singularity c. a time-stopping point d. a black dwarf e. Bayonne, New Jersey

b. a singularity

According to the general theory of relativity, light and other radiation coming from a white dwarf or a neutron star should (and experiments show that it does) exhibit a. reddening, where the bluer colors are more effectively absorbed or scattered by dust b. a very strong blue shift c. motion in a perfect circle around the white dwarf and neutron star d. a gravitational redshift e. absolutely no difference in characteristics when compared to light coming from any star

d. a gravitational redshift

The first, indirect detection of gravitational waves in the 1970s involved a. a pulsar that was in the same star system with a neutron star b. the black hole in the Cygnus X-1 system c. a star that was swelling up to be the largest red giant astronomers had ever seen d. a spacecraft that we purposely sent to fall into the strong gravity of the Sun e. the collapse of a huge garbage dump in the town of Bayonne, New Jersey

a. a pulsar that was in the same star system with a neutron 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. a K-type star d. an M-type star e. you can't fool me, all spectral types on the main sequence have an equal chance of becoming black holes

a. an O-type star

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. a distortion in spacetime caused by the gravity of the Sun c. the pull of a small black hole that orbits our Sun so closely that we are not able to see it d. the presence of a strong magnetic field in the Sun, which causes huge outburst of material e. a distortion in our view of the solar system caused by the Earth's atmosphere

b. a distortion in spacetime caused by the gravity of the Sun

The first time that astronomers observed both gravitational waves and electro-magnetic waves from the same event, what they were observing was: a. a supernova explosion in one of the closest galaxies to us b. the spiraling toward each other of two neutron stars c. a binary star system where a giant star is overloading a white dwarf with too much material d. the merger of two black holes with masses dozens of times the mass of our Sun e. the collapse of an entire cluster of stars into one big black hole

b. the spiraling toward each other of two neutron stars

Which of the following statements about the way the mass of a white dwarf affects spacetime is correct? a. the white dwarf mass will attract light, and pull it in a curved path; spacetime is not affected b. the white dwarf mass will curve spacetime; light has to follow that curvature c. the white dwarf mass will not affect spacetime at all; only black holes affect spacetime 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. since no experiments have ever tested Einstein's theory of general relativity, it is impossible to say what will happen

b. the white dwarf mass will curve spacetime; light has to follow that curvature

Some years after college (and after you recover from your astronomy class,) you get married and exchange gold rings with your sweetheart. What connection is there between the gold in those rings and recent observations of gravitational waves? a. gold atoms are only produced in supernova explosions, and all the gravitational wave events we have detected so far are from supernovae b. gold is so valuable (and so rare) because there it is only produced in the accretion disks of black holes, and most of it falls into the black hole c. our new understanding is that significant amounts of gold in the universe are produced in the mergers of neutron stars, which can be detected with gravitational waves d. gold is produced when two black holes merge, and most of the gravitational waves we have detected are from black hole mergers e. this is a misleading question; there is no connection whatsoever between gold and gravitational wave events

c. our new understanding is that significant amounts of gold in the universe are produced in the mergers of neutron stars, which can be detected with gravitational waves

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

d. causes a curvature (or warping) of spacetime

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 neutron star radius c. the gravitational redshift zone d. the event horizon e. day-time television

d. the event horizon

Which of the following can a black hole not"eat" (swallow)? a. a planet b. a cloud of gas and dust c. a star d. another black hole e. you can't fool me, black holes can eat anything

e. you can't fool me, black holes can eat anything

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

b. the mass inside the event horizon

The astronomer who first worked out the mathematical description of black hole event horizons was a. Edwin Hubble b. Jocelyn Bell c. Karl Schwarzschild d. S. Chandrasekhar e. Frederik Pohl

c. Karl Schwarzschild

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. Putting aside practical considerations (such as the fact that we cannot travel to other stars), which of the following strategies would IN THEORY allow him to age more slowly than the rest of humanity. a. he should always live at sea level on Earth, and never go to any mountains or high altitudes b. he should live far away from the gravity of any planet or star (in a deep-space station) c. he should be in orbit around the Earth, and expose himself to as many cosmic rays as possible d. he should travel to a black hole, and spend some time in orbit just above the event horizon e. he should live in a room filled with positive electrical charge

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

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

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

When astronauts aboard the International Space Station (ISS) in space let go of an orange, it just floats there. Why is that? a. the ISS is so far from the Earth, the gravity there is essentially zero b. the ISS is falling around the Earth, and in free fall, things feel no weight c. spacetime is so different aboard the ISS, that time stops, and so nothing can fall d. the law of gravity only works on the Earth, it doesn't work in space e. this is an unsolved problem in science, and so it is "fruitless" to worry about it

b. the ISS is falling around the Earth, and in free fall, things feel no weight

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 inside the black hole event horizon b. from the photosphere of the companion star (the star that is not a black hole) c. from the singularity d. 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) e. 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)

d. 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)

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

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

When scientists say that "black holes have no hair", what do they mean? a. that the event horizon of a black hole is very smooth and does not have parts that jut out b. that if you threw something toward a black hole (a rabbit, say) it would quickly be ripped apart into smaller pieces c. that time near a black hole slows down so much our hair would not grow at a normal rate d. that once a black hole forms, very little information can be extracted from it about the material that is now inside e. no one knows what this means; regular people are not meant to figure out some of the weird things physicists say about black holes

d. that once a black hole forms, very little information can be extracted from it about the material that is now inside

When a light wave leaves a region of strong gravity, compared to the same wave leaving a spaceship in empty space, the wave in strong gravity will have a. a longer wavelength b. a lower frequency c. less energy d. a gravitational redshift e. all of the above

e. all of the above