Unit 3 Exam
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
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
a. an invisible halo made of what astronomers are calling "dark matter"
According to the models of the universe we discussed in this course, why do the galaxies move apart (why do we have Hubble's law)?
a. as a result of the Big Bang, space itself is stretching, and this stretching carries the galaxies away from each other
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?
a. because the SMC is small and its stars are widely spaced, the rate of star formation (and star death) is much slower there
Which of the following is the Earth not located in?
a. globular cluster M-13
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
a. hydrogen
If a galaxy contains a great deal of "dark matter," what will that do the galaxy's mass-to-light ratio?
a. increase it quite a bit
The reciprocal of the Hubble constant (1/H) is a rough measure of the:
a. the age of the universe
The two scientists who first discovered the cosmic microwave background radiation were:
c. Penzias and Wilson
Which of the following statements about dark matter in the Galaxy is FALSE?
c. While the dark matter cannot be observed with our present-day instruments, we still have a pretty good idea what it consist of
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")?
c. a new kind of subatomic particle
In describing the universe using his equations of general relativity, Einstein assumed that it was isotropic (the same in all directions.) What recent observations have confirmed that the universe is isotropic on the large scale?
e. measurements of the 3-degree cosmic background radiation
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?
e. measuring the Doppler shift of a line in a radio spectrum
Our Milky Way Galaxy is what type of galaxy?
e. spiral
The Andromeda Galaxy (our nearest spiral neighbor) has spectral lines that show a blue shift. From this we may conclude that:
a. this particular nearby galaxy is moving toward us
Which of the following is NOT a characteristic of a spiral galaxy?
a. when we take spectra of its stars, they have far less of the heavier elements than the Sun
One of the things that our current "standard model" of the Big Bang Theory doesn't explain is
e. why the temperature of the cosmic microwave background is so uniform throughout all of space
Scientists looking at an overview of physics today understand that there are four forces that govern all action in the universe. These four forces are the strong nuclear force, the weak nuclear force, electro-magnetism and
gravity
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:
b. elliptical
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?
b. galaxies contain many more stars that shine much less brightly than the Sun
A "galactic year" as defined by astronomers is:
c. the time it takes the Sun to revolve once around the center of the Milky Way Galaxy
Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify galaxies?
c. their shape
How do astronomers measure the mass that the Galaxy contains inside the orbit of the Sun?
c. 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
Before you can use Hubble's Law to get the distance to a galaxy, what observation must you make of that galaxy?
c. you must take a spectrum of the galaxy and measure the red shift
The first scientist to propose a specific model (the primeval atom model) for the big bang was
d. Lemaitre
The standard bulbs (standard candles) that made it possible for astronomers to discover the acceleration in the expansion of the universe were
d. Type Ia supernovae
Objects orbiting around the center of the Milky Way obey Kepler's 3rd Law. This means that:
d. a cloud of gas or star that is further from the center will generally take more time to orbit
Which of the following statements about the early universe (as envisioned by the standard model of cosmology) is FALSE?
d. at the very beginning, the energies were so great that the universe was actually contracting for a while
Today, we believe that only a small number of elements were actually formed during the Big Bang. Which of the following was NOT one of these:
d. carbon
The type of galaxy that sometimes has a distinct bar of stars running across the central region is
d. spiral
Which of the following statements about the nuclear bulge of our Galaxy is FALSE?
d. the best way to learn more about it is to observe higher energy radiation, such as ultraviolet and x-rays
According to the most recent data from satellites making precise measurements of the properties of the cosmic background radiation (CBR),
d. the dark energy makes up just a little less than 70% of the density of the universe, making it the most significant constituent of the mass-energy
Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is from us, the
d. the faster it is moving away from us
Why did Einstein introduce the cosmological constant into the equations of his General Theory of Relativity when describing the universe?
e. Einstein's equations required the universe to expand or contract; he could not imagine or accept it doing either one, so he put a factor in to stop it from moving
The satellite that has given us the most precise measurements of the characteristics of the cosmic background radiation is:
e. Planck
The first astronomer to show that spiral nebulae (today called spiral galaxies) have large Doppler shifts was
e. Vesto Slipher
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?
e. a radio telescope that can observe at 21-cm wavelengths
How does a period of extremely fast inflation very early in the history of the universe explain the observation that the geometry of the universe looks flat (not curved) to us?
e. inflation increased the size of the universe so much that the resulting universe looks flat from any point of view
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. a central bulge with a bar of stars in the middle
If you want to check on what conditions were like in the universe a few hundred thousand years after the Big Bang, what sort of instrument would it be best to use:
a. a satellite with infrared and microwave telescopes on board
Factoring in everything we currently know about the history of the universe, our best estimate for the age of the universe is
a. about 13.8 billion years
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?
a. about 17 times the size of the Sun
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?
a. by observing a Cepheid variable in a nearby galaxy and using it to get the distance
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?
a. finding Cepheid variables and measuring their periods
Which of the following did NOT happen during the first few minutes after the Big Bang?
a. some very massive early stars formed
Astronomers have measured that there is more helium in the universe than can be explained by the fusion in stars over the last 13 billion years. How do they think the extra helium got into the universe?
a. the extra helium was made during the first few minutes of the Big Bang, when the entire universe was hot enough for fusion to occur briefly
If we include the effects of deceleration in our calculations of the age of the universe, the age we get is:
b. less than the Hubble time
Based on many surveys of the average density of matter in the universe (regular matter and dark matter), astronomers now conclude that the average density of the universe is
b. less than the critical density
The Tully-Fisher relation (looking at rotation speeds) only works for:
b. spiral galaxies
Which of the following is evidence that the formation process of our Galaxy may have included collisions with smaller neighbor galaxies?
c. the observation of long moving streams of stars that continue to orbit through our Galaxy's halo
What leads astronomers to conclude that the proto-galactic cloud (the cloud from which our Galaxy formed) was roughly spherical?
c. 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 our modern theories, the geometry of the entire universe (all of space-time) may be curved or warped. This is a pretty bizarre notion; what other discovery in astronomy has helped us believe that space may be able to curve or warp?
c. the properties of black holes
When we determine the age of the universe using the Hubble Time, what important simplifying assumption goes into our calculations?
d. that we have accounted correctly for the effects of dark energy
Some scientists speculate that our universe is not the only universe that exists, but the only one we can gather evidence about. This idea is called
d. the multiverse theory
The astronomer who assisted Edwin Hubble at the Mount Wilson Observatory and helped him establish the expansion of the universe was:
a. Milton Humason
According to our textbook, roughly what percent of the mass and energy contents of the universe is made up of dark matter plus dark energy?
b. 95 percent
The first satellite (spacecraft with instruments) to measure and confirm the cosmic microwave background was the:
b. COBE (COsmic Background Explorer)
The Population I stars in the Milky Way Galaxy
b. all of the above
In the very distant future, given our best model of the accelerating universe, what will the universe look like?
b. all the stars will die and the galaxies will be dark
Which of the following statements about dark matter is FALSE:
b. astronomers have a pretty good idea what the dark matter is made of
Which of the following was not done by Edwin Hubble?
c. discovering the relationship between period and luminosity of a cepheid variable
Which type of galaxy is observed to contain mostly older stars?
c. elliptical
What method would astronomers use to find the distance to a galaxy so far away that individual stars are impossible to make out (resolve)?
c. finding the redshift and using Hubble's Law
The new instrument that made it possible for Edwin Hubble to demonstrate the existence of other galaxies in the early 1920's was:
c. the 100-inch reflector on Mount Wilson
Which of the following is pretty good evidence that the universe began with a Big Bang?
c. the 3-degree cosmic microwave background radiation
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?
c. the Hubble Space Telescope has shown us a visible-light image of an accretion disk at the center of the Galaxy
Scientists speculate that the properties (laws) of the universe must be the way they are because if they were significantly different, we would not be here to think about them. This idea is called
c. the anthropic principle
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?
c. 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
Where in space did the expansion of the universe begin?
d. everywhere at once
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?
d. find a variable star (cepheid or RR Lyrae) in the cluster
Which of the following statements about the implications of Hubble's Law is FALSE?
d. 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
What was especially noteworthy about the Sagittarius Dwarf Galaxy when it was discovered among the small galaxies near the Milky Way?
d. it was on a collision course with the Milky Way and would be swallowed by it eventually
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
d. more
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
d. move away from us three times faster than A
At about 1 second after the beginning of the universe, one type of particle was able to start traveling freely through the universe. These particles are still with us, but they are extremely hard to detect. They are called:
d. neutrinos
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?
d. obtain the speed at which stars or gas near the outer regions of the galaxy are moving around
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
c. Galileo Galilei
Why is the use of Hubble's Law to measure distances to galaxies so important to astronomers?
c. Most galaxies are so far away, the only way to get distances to them is to use Hubble's Law
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?
c. a peanut
Compared to the mass of our own Milky Way Galaxy, the total mass we estimate for the Andromeda Galaxy is
e. somewhat bigger
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?
e. 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
Recent observations indicate that the universe is expanding faster today than it was a few billion years ago (that, in other words, the expansion of the universe is accelerating.) What kind of observations have led astronomers to this surprising conclusion?
e. the measurement of galaxy distances using Type Ia supernovae
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?
e. 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?
e. they are (for galaxies) very close to us, so they are easy to study
The model of the universe that involves an enormous increase of scale during a very short time in the early universe is called:
b. the inflationary universe model
What is the strongest known force in the universe?
b. the strong nuclear force
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?
c. Orion Spur
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?
c. all of the above
At first, right after the Big Bang, the universe was too hot for nuclei and electrons to combine into the kinds of neutral atoms that are familiar to us today. How soon after the beginning did it become cool enough for neutral atoms to form?
e. a few hundred thousand years
In our modern view of the expansion of the universe, we understand that it is space that is stretching; individual galaxies don't speed away from each other as if they were rockets. In that case, why do galaxies show a red-shift?
e. as space stretches, the waves of radiation in space also stretch and their wavelength increases
Which of the following statements about the different types (shapes) of galaxies is correct?
e. collisions and mergers between galaxies can sometimes change a galaxy's type (shape)
Which type of galaxy is very difficult to see, but (astronomers recently realized) may be very common?
e. dwarf elliptical
What objects did Harlow Shapley use as "signposts" to figure out the extent of the Milky Way Galaxy and the location of its center?
e. globular clusters
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?
e. in a globular cluster high above the Galaxy's disk
Where would you look for the youngest stars in the Milky Way Galaxy?
e. in the disk
The Tully-Fisher method for measuring the distance to galaxies relies on the observed relationship between the luminosity of a spiral galaxy and
e. its rotational velocity (as determined from the width of the 21-cm line)
The reason type Ia supernovae are useful to astronomers for determining distances to other galaxies is that
e. they are very bright, and generally reach the same peak luminosity
Which of the following objects is considered useful to astronomers as a "standard bulb" for determining distances?
e. type Ia supernovae
What have we learned from the work of Harlow Shapley and others about the location of the Sun in the Milky Way Galaxy?
e. we are in the disk of the Galaxy, about 3/5 of the way from the center
