Semester 2 Astronomy (Chapters #24-26) ALL QUESTIONS
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 longer wavelength - a lower frequency - less energy - a gravitational redshift (all of the above)
The Population I stars in the Milky Way Galaxy
- include the Sun - show a wider range of ages than Population II stars - generally contain a greater percentage of heavier elements than Population II stars - are generally found in the disk of the Galaxy (all of the above)
From which of the following will a wave of light show the greatest gravitational redshift:
a white dwarf
Which of the following was not done by Edwin Hubble?
discovering the relationship between period and luminosity of a cepheid variable
Which type of galaxy is observed to contain mostly older stars?
elliptical
The reason type Ia supernovae are useful to astronomers for determining distances to other galaxies is that
they are very bright, and generally reach the same peak luminosity
How do astronomers measure the mass that the Galaxy contains inside the orbit of the Sun?
they measure the distance to the center of the Galaxy and the period of the Sun's orbit and then use Kepler's Third Law
The Andromeda Galaxy (our nearest spiral neighbor) has spectral lines that show a blue shift. From this we may conclude that:
this particular nearby galaxy is moving toward us
Which of the following objects is considered useful to astronomers as a "standard bulb" for determining distances?
type Ia supernovae
Which of the following can a black hole not "eat" (swallow)?
you can't fool me, black holes can eat anything
Which of the following objects do many astronomers believe is a black hole?
Cygnus X-1
The astronomer who first worked out the mathematical description of black hole event horizons was
Karl Schwarzschild
The type of galaxy that consists almost entirely of old stars and is thus less blue (more yellow and reddish) than the other types is:
elliptical
In a distant galaxy, whose light is just arriving from 10 billion light years away, our spectroscope should reveal that the most common element is
hydrogen
Which of the following is evidence that the formation process of our Galaxy may have included collisions with smaller neighbor galaxies?
the observation of long moving streams of stars that continue to orbit through our Galaxy's halo
The first time that astronomers observed both gravitational waves and electro-magnetic waves from the same event, what they were observing was:
the spiraling toward each other of two neutron stars
A "galactic year" as defined by astronomers is:
the time it takes the Sun to revolve once around the center of the Milky Way Galaxy
In the future, astronomers believe that the Milky Way Galaxy has additional collisions in store. Which of the following nearby galaxies are eventually going to collide with our own?
- the Small Magellanic Cloud - the Large Magellanic Cloud - the Andromeda Galaxy (M-31) (all of the above)
The scientist who made the first telescopic survey of the Milky Way and discovered that it is composed of a huge number of individual stars was
Galileo Galilei
The astronomer who assisted Edwin Hubble at the Mount Wilson Observatory and helped him establish the expansion of the universe was:
Milton Humason
Why is the use of Hubble's Law to measure distances to galaxies so important to astronomers?
Most galaxies are so far away, the only way to get distances to them is to use Hubble's Law
Your weird cousin, who is really into astronomy, decides that the return address he uses on his letters is incomplete! To his city, state, and country, he begins to add: "North America, Earth, Solar System..." If he now wants to include the name of the Galaxy's spiral-structure feature in which the Earth is located, how should his address end?
Orion Spur
The very strong source of radio waves at the center of our Galaxy is called
Sagittarius A
The first astronomer to show that spiral nebulae (today called spiral galaxies) have large Doppler shifts was
Vesto Slipher
Which of the following statements about dark matter in the Galaxy is FALSE?
While the dark matter cannot be observed with our present-day instruments, we still have a pretty good idea what it consist of
Astronomers now think that there is a black hole with more than 4 million times the mass of our Sun at the center of our Galaxy? Roughly how large would the event horizon of such a supermassive black hole be?
about 17 times the size of the Sun
What type of main sequence star is most likely to become a black hole?
an O-type star
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?
an entire galaxy of stars (with about a billion stars in it)
Astronomers now know that surrounding the main body of our Galaxy (which our various kinds of telescopes have shown to us) and our fainter halo of stars there is
an invisible halo made of what astronomers are calling "dark matter"
One of the most important observations in the history of astronomy was the one by Edwin Hubble that established that there are other galaxies, quite removed from the Milky Way. How did Hubble show this?
by observing a Cepheid variable in a nearby galaxy and using it to get the distance
When Einstein proposed his General Theory of Relativity, he suggested some pretty strange ideas about space, time, and gravity. How did scientists in 1919 show that Einstein's theory described the behavior of the real world and wasn't just a crazy hypothesis?
by observing starlight coming close to the Sun during an eclipse
According to the general theory of relativity, the presence of mass
causes a curvature (or warping) of spacetime
Which of the following statements about the different types (shapes) of galaxies is correct?
collisions and mergers between galaxies can sometimes change a galaxy's type (shape)
An astronomer needs to measure the distance to a globular cluster of stars that is part of the Milky Way Galaxy. What method should she try to use to find the distance?
find a variable star (cepheid or RR Lyrae) in the cluster
One of the main projects being carried out by the Hubble Space Telescope is to measure the distances of galaxies located in groups dozens of millions of lightyears away. What method do astronomers use with the Hubble to find such distances?
finding Cepheid variables and measuring their periods
What method would astronomers use to find the distance to a galaxy so far away that individual stars are impossible to make out (resolve)?
finding the redshift and using Hubble's Law
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?
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)
Which is one reason that the typical galaxy's mass-to-light ratio (in units of the Sun's mass over the Sun's luminosity) generally greater than 1?
galaxies contain many more stars that shine much less brightly than the Sun
The Tully-Fisher method for measuring the distance to galaxies relies on the observed relationship between the luminosity of a spiral galaxy and
its rotational velocity (as determined from the width of the 21-cm line)
To predict whether a star will ultimately become a black hole, what is the key property of the star we should look at?
mass
Radio astronomy has played a pivotal role in showing us the detailed structure of the Milky Way Galaxy. Which of the following techniques would a radio astronomer use as an essential part of an investigation of this structure?
measuring the Doppler shift of a line in a radio spectrum
If a galaxy contains a great deal of dark matter, then, compared to the mass-to-light ratio of the inner part, the mass-to-light ratio of the whole galaxy will be
more
Once a black hole forms, the size of its event horizon is determined only by
the mass inside the event horizon
What have we learned from the work of Harlow Shapley and others about the location of the Sun in the Milky Way Galaxy?
we are in the disk of the Galaxy, about 3/5 of the way from the center
Which of the following is NOT a characteristic of a spiral galaxy?
when we take spectra of its stars, they have far less of the heavier elements than the Sun
Astronomers today know a lot about the size and shape of the Milky Way Galaxy. Which of the following common objects most resembles the shape of our Galaxy?
a CD or DVD
About two thirds of the nearby spiral galaxies (which we can study in more detail) don't have a round central bulge, but instead show
a central bulge with a bar of stars in the middle
Objects orbiting around the center of the Milky Way obey Kepler's 3rd Law. This means that:
a cloud of gas or star that is further from the center will generally take more time to orbit
Einstein suggested that the regular change (advance) in the perihelion of the planet Mercury could be explained by:
a distortion in spacetime caused by the gravity of the Sun
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 gravitational redshift
Astronomers making observations in our Galaxy have been able to rule out a number of suggestions for what the dark matter in the Galaxy might be. Which of the following have we NOT been able to rule out (which suggestion is still "in the running")?
a new kind of subatomic particle
The central region of our Galaxy is not as flat as its main disk of stars. Which of the following has roughly the same shape as our central region of stars?
a peanut
The first, indirect detection of gravitational waves in the 1970s involved
a pulsar that was in the same star system with a neutron star
You suddenly get an uncontrollable urge to find out more about the other side of the Milky Way Galaxy (the regions beyond the center). Where should you rush off to?
a radio telescope that can observe at 21-cm wavelengths
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 singularity
Astronomers have concluded that growing supermassive black holes (which have millions of times the Sun's mass or more) is pretty unlikely at our location in the Milky Way Galaxy. Where do they think is the most likely place in the Milky Way for such a supermassive black hole?
at the center of the Milky Way Galaxy, where matter is more crowded
Astronomers observe the Small Magellanic Cloud (SMC), a not very dense, rather small galaxy near us. They notice that even those stars that formed recently have relatively few heavier elements (when compared to such recent stars in our Milky Way.) What is the likely explanation for this deficiency?
because the SMC is small and its stars are widely spaced, the rate of star formation (and star death) is much slower there
Which type of galaxy is very difficult to see, but (astronomers recently realized) may be very common?
dwarf elliptical
If you are in a freely falling elevator near the top of a tall building, as the elevator falls, your weight would be:
equal to zero - you would be weightless
What objects did Harlow Shapley use as "signposts" to figure out the extent of the Milky Way Galaxy and the location of its center?
globular clusters
What is a key reason that gravitational waves are so much harder to detect than electro-magnetic (e-m) waves?
gravitational waves are much weaker than e-m waves, and therefore require very, very precise equipment to detect
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.
he should travel to a black hole, and spend some time in orbit just above the event horizon
Which of the following statements about the implications of Hubble's Law is FALSE?
if you were observing the universe from a distant galaxy, you would NOT see all the galaxies (except those in your own group) moving away from YOU
If I want to find a sizeable collection of Population II stars in the Milky Way Galaxy, where would be a good place to look?
in a globular cluster high above the Galaxy's disk
Where would you look for the youngest stars in the Milky Way Galaxy?
in the disk
If a galaxy contains a great deal of "dark matter," what will that do the galaxy's mass-to-light ratio?
increase it quite a bit
What was especially noteworthy about the Sagittarius Dwarf Galaxy when it was discovered among the small galaxies near the Milky Way?
it was on a collision course with the Milky Way and would be swallowed by it eventually
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:
more slowly
According to Hubble's Law, if two galaxies are not part of our Local Group, and galaxy B is three times farther away from us as Galaxy A, then Galaxy B will
move away from us three times faster than A
A graduate student in astronomy needs to measure the mass of a spiral galaxy she is studying for her PhD thesis. Which of the following observations would be important for her to make?
obtain the speed at which stars or gas near the outer regions of the galaxy are moving around
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?
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
Far away from a black hole (at the distance of another star), which of the following is a possible way to detect it?
search for flickering x-rays being given off from an accretion disk around the black hole, as it "eats" part of a neighbor star
Compared to the mass of our own Milky Way Galaxy, the total mass we estimate for the Andromeda Galaxy is
somewhat bigger
Our Milky Way Galaxy is what type of galaxy?
spiral
The type of galaxy that sometimes has a distinct bar of stars running across the central region is
spiral
The Tully-Fisher relation (looking at rotation speeds) only works for:
spiral galaxies
When scientists say that "black holes have no hair", what do they mean?
that once a black hole forms, very little information can be extracted from it about the material that is now inside
The new instrument that made it possible for Edwin Hubble to demonstrate the existence of other galaxies in the early 1920's was:
the 100-inch reflector on Mount Wilson
Which of the following is NOT part of the growing chain of evidence that makes many astronomers suspect there is a black hole at the very center of the Milky Way Galaxy?
the Hubble Space Telescope has shown us a visible-light image of an accretion disk at the center of the Galaxy
When astronauts aboard the International Space Station (ISS) in space let go of an orange, it just floats there. Why is that?
the ISS is falling around the Earth, and in free fall, things feel no weight
Which of the following statements about the nuclear bulge of our Galaxy is FALSE?
the best way to learn more about it is to observe higher energy radiation, such as ultraviolet and x-rays
Astronomers believe that the center of our Galaxy has a black hole with enough mass inside to make almost 4 million Suns! How do astronomers think a black hole could acquire so much mass?
the center of our Galaxy is a much more crowded region than where the Sun is found; we still see material falling toward the center and material has fallen in for billions of years
In 1959, Pound and Rebka did an experiment to test the prediction of Einstein's theory of general relativity about the relationship between the pace of time and the strength of gravity. When two identical atomic clocks, one on the ground floor and one on the top floor, were compared,
the clock on the ground floor ran a tiny bit slower
William Herschel thought that the Sun and Earth were roughly at the center of the great grouping of stars we call the Milky Way. Today we know this is not the case. What was a key reason that Herschel did not realize our true position in the Milky Way?
the dust that extends throughout the disk of the Galaxy only allowed Herschel to see the small part of the Milky Way that surrounds us
The equivalence principle (principle of equivalence) says that
the effects of gravity are equivalent to the effects of acceleration
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
the event horizon
Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is from us, the
the faster it is moving away from us
In the first direct detection of gravitational waves by LIGO in 2015, the waves came from
the merger of two black holes
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?
the message will never emerge from the event horizon
What leads astronomers to conclude that the proto-galactic cloud (the cloud from which our Galaxy formed) was roughly spherical?
the oldest stars in the Galaxy (Population II stars, globular clusters) form a spherical halo around the Galaxy; they outline the original shape of the cloud that gave the Galaxy birth
According to Einstein's general theory of relativity, the stronger a star's gravity,
the slower time runs near it
Which of the following statements about the way the mass of a white dwarf affects spacetime is correct?
the white dwarf mass will curve spacetime; light has to follow that curvature
Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify galaxies?
their shape
Recently, astronomers have observed stars and other objects that orbit the center of the Milky Way Galaxy farther out than our Sun, but move around faster than we do. How do astronomers think such an observation can be explained?
there must be a great deal of invisible dark matter outside the orbit of the Sun whose gravitational pull explains the faster motions we see out there
Among irregular galaxies, what makes the Large and Small Magellanic Cloud especially useful for astronomers?
they are (for galaxies) very close to us, so they are easy to study
Before you can use Hubble's Law to get the distance to a galaxy, what observation must you make of that galaxy?
you must take a spectrum of the galaxy and measure the red shift
