Exam 3- Galaxies
Astronomers can now report that active star formation was going on at a time when the universe was only 20% as old as it is today. When astronomers make such a statement, how can they know what was happening inside galaxies way back then? a.) they look at radio waves coming from nearby active galaxies b.) they examine the spectra of galaxies (or the overall colors of galaxies) with the highest redshifts they can find c.) they look at the open clusters in the Milky Way Galaxy d.) they look at the elements in comets, which formed when our solar system was first forming e.) they look at a graph that shows the way galaxy redshifts change with time
b
Before you can use Hubble's Law to get the distance to a galaxy, what observation must you make of that galaxy? a.) you must find a Cepheid variable star in the galaxy b.) you must take a spectrum of the galaxy and measure the red shift c.) you must measure how strongly the galaxy emits radio waves at a wavelength of 21 centimeters d.) you must find a Type Ia supernova that is exploding in that galaxy e.) all you need to do is look at the galaxy through any telescope
b
Galaxies that we see as they were 11 billion years ago or more, as compared to galaxies today, are generally: a.) bluer and larger b.) bluer and smaller c.) redder and larger d.) redder and smaller e.) pretty much the same
b
The "great voids" that astronomers studying galaxies are finding are: a.) regions where a number of black holes have cleared out space in the center of a galaxy b.) very large regions of intergalactic space, where relatively few galaxies or galaxy clusters can be found c.) empty regions between the spiral arms of the Milky Way Galaxy d.) huge regions inside spiral galaxies, where the powerful radiation from a very hot star has cleared out the local interstellar material
b
The type of galaxy that sometimes has a distinct bar of stars running across the central region is a.) all of the above can have clear, distinct central bars b.) spiral c.) elliptical d.) irregular
b
What do the surveys of the three-dimensional distribution of groups of galaxies reveal about how groups and clusters of galaxies are organized? a.) galaxy groups make a huge spiral structure that resembles the Milky Way (but is much bigger) b.) galaxy groups are organized into huge filaments with great voids between them -- something like the structure one would see taking a cross-section of some soap bubbles c.) galaxy groups are organized into huge spherical "lumps" with concentric rings of groups of galaxies around each lump d.) you can't fool me; astronomers cannot get any sense with our present-day instruments of how groups of galaxies are distributed on the large scale e.) galaxy groups are distributed completely evenly -- there is typically the same amount of space between them -- and so there is no structure evident
b
What is the Hubble tuning fork diagram? a.) A classification system for different types of galaxies based on their differences in rotation speeds. b.) A classification system for different types of galaxies based on their differences in visual appearance. c.) An evolutionary sequence for different types of galaxies moving from elliptical to spiral. d.) An evolutionary sequence for different types of galaxies moving from spiral to elliptical.
b
Which of the following is NOT a characteristic of a spiral galaxy? a.) it has quite a bit of gas and dust in it b.) when we take spectra of its stars, they have far less of the heavier elements than the Sun c.) the bright stars in it can be seen organized into distinct spiral arms d.) it has young stars and bright emission nebulae e.) most of its material is in the shape of a flattened disk
b
Which of the following statements about our modern ideas of how spiral galaxies form and develop is TRUE? a.) star formation in the spiral galaxies is much higher today than it was 8 billion years ago b.) spiral galaxies have evolved until today they are all "red and dead", containing just old stars and showing almost no current star formation c.) spiral galaxies formed pretty quickly after the Big Bang and already looked then the way they look today d.) the central bulges of spiral galaxies formed first and their disks formed later e.) spiral galaxies cannot have a central super-massive black hole, so astronomers don't understand just how they formed
d
According to our current understanding, giant elliptical galaxies form: a.) when a black hole swallows enough material so that most of the stars in the galaxy are inside the black hole, leaving only a thin halo b.) by the merger (or swallowing) of a number of smaller galaxies in a cluster of galaxies c.) only in the giant voids that astronomers are discovering among the filaments and chains of galaxies d.) by being located near the center of the Big Bang explosion and thus getting a major early push
b
An astronomer is observing a distant galaxy which looks blue. Which of the following can she conclude from this observation? a.) the galaxy must be extremely large (probably a giant elliptical) b.) the galaxy must contain only older stars (those that formed billions of years ago) c.) the galaxy must be rotating very slowly or not at all d.) the galaxy must have a lot of star formation going on at the time we are seeing it e.) the galaxy must be moving toward us (must have a blue shift)
d
Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify galaxies? a.) their abundance of the element iron b.) their brightness c.) their Doppler Shift d.) their shape e.) their overall color
d
Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is from us, the a.) the larger its halo is b.) brighter it looks c.) the later in its life we are seeing it d.) the faster it is moving away from us e.) bluer its color
d
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.) Oxygen b.) Helium c.) Carbon d.) Hydrogen
d
One important way astronomers can learn in some detail about what happens when galaxies collide is a.) to look at videos of car accidents that are particularly violent b.) to look at the supermassive black hole at the center of the Milky Way c.) to watch the Andromeda Galaxy (M31,) which is on a collision course with us, for a decade d.) to simulate galaxy collisions on a large computer and watch what the simulation predicts e.) examine the satellite galaxies presently orbiting the Milky Way
d
Which of the following does NOT happen when two galaxies collide? a.) the rate of star formation increases b.) the shape of the galaxy is often changed c.) large interstellar gas clouds collide d.) many of the stars in one galaxy collide with the stars in the other e.) a smaller galaxy may wind up inside a larger one
d
Which of the following is not true about the Local Group of galaxies (of which the Milky Way is a member)? a.) it has few galaxies when compared to a rich cluster b.) it has more elliptical galaxy members than spiral galaxies c.) it is a member of the same supercluster as the Virgo Cluster d.) it has about a thousand member galaxies e.) the Milky Way is one of its more massive members
d
Which type of galaxy is very difficult to see, but (astronomers recently realized) may be very common? a.) Spiral b.) Irregular c.) Dwarf Elliptical d.) none of the above e.) Elliptical
c
To map out how clusters of galaxies are distributed in the universe, astronomers needed to know where each cluster was in the sky AND a.) whether any of the galaxies in each cluster acted like quasars b.) how many galaxies were in each cluster c.) how blue or red the galaxies in each cluster were d.) how far away from us each cluster was
d
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 a.) move away from us three times faster than A b.) move away from us nine times faster than A c.) move away from us at about the same speed as A d.) move toward us nine times faster than A e.) move toward us three times faster than A
a
Astronomers believe that the large elliptical galaxies formed a.) from the collision and merger of many smaller fragments b.) only recently, less than a billion years ago (before that galaxies were spirals) c.) right after the Big Bang, looking just like they look today d.) without the presence of any super-massive black holes
a
By examining rich clusters of galaxies, such as the Coma Clusters, astronomers have discovered that spiral galaxies a.) are found mostly in the outer regions of such clusters, not in the middle b.) grow to be very large and bright at the centers of these clusters c.) do not exist at all in such clusters d.) turn out to be most of the galaxies in such clusters, and many are found throughout each cluster e.) are all tilted exactly the same way in such cluster; all their disks are fully aligned
a
How do astronomers currently think the amount of detectable (observable) matter in the universe compares to the amount of dark matter and dark energy? (Be careful here, we're taking dark energy into account) a.) the amount of detectable matter is far less than the amount of dark matter & energy (<5%) b.) the amount of detectable matter is about 1/10th the amount of dark matter & energy c.) the amount of detectable matter is far greater than the amount of dark matter & energy d.) there is no evidence for dark matter anywhere, so this is not a topic astronomers can make any estimates about e.) the amount of detectable matter is about equal to the amount of dark matter & energy
a
If I looked on a large scale and plotted the position of galaxy clusters, I would find them arranged: a.) in filaments and empty areas like a web b.) perfectly smoothly with even spacing c.) around the Milky Way, the most massive galaxy
a
If a very distant galaxy looks blue overall to astronomers, from this they can conclude that: a.) the galaxy must have a lot of young stars and thus active star formation must still be going in it b.) the galaxy is moving toward us at great speed c.) the galaxy must not be especially massive when compared to most galaxies d.) the galaxy must be composed mostly of very old stars
a
Roughly how many galaxies make up our Local Group? a.) about 60 or so b.) millions c.) many hundreds d.) only three e.) thousands
a
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: a.) elliptical b.) barred spiral c.) all of the above consist almost entirely of old stars d.) spiral e.) irregular
a
When astronomers have examined rich clusters of galaxies with their instruments, they have found that these clusters a.) are more likely to contain giant elliptical galaxies than poor clusters b.) contain mostly galaxies dominated by the light of young stars (stars formed recently) c.) are the only places in the universe where galaxies find a way NOT to collide d.) contain far more spiral galaxies in their central regions than elliptical galaxies e.) are so big that there is a lot more space between the galaxies than in poor clusters like our Local Group
a
Which of the following is not a way that astronomers can find how much dark matter there is in cluster of galaxies? a.) observing x-rays from the hot gas in the cluster, and using the amount of x-ray radiation to estimate the mass of the cluster b.) observe the radio waves coming from all dark matter; from the strength of the radio waves from each cluster, estimate the amount of dark matter needed to produce them c.) using gravitational lensing effects to make a map of how much mass a cluster of galaxies contains d.) measuring the speeds with which the galaxies are moving around, to estimate the mass of the cluster needed to keep them from moving away e.) measuring how much slower galaxies in a rich cluster or supercluster are moving than the Hubble Law would predict
b
Which of the following statements about the different types (shapes) of galaxies is correct? a.) 90% of all galaxies are spirals (including our Milky Way); the other two types are very unusual b.) collisions and mergers between galaxies can sometimes change a galaxy's type (shape) c.) what type we see a galaxy to be just depends on the angle at which we happen to see it; all galaxies look roughly the same in shape d.) all galaxies start out as ellipticals, but some later evolve to be spirals and irregulars e.) whatever type a galaxy is at its birth, that's what it will be for all time
b
Among irregular galaxies, what makes the Large and Small Magellanic Cloud especially useful for astronomers? a.) they do not contain any young stars at all, only really old ones b.) they are among the biggest irregular galaxies ever found c.) they are (for galaxies) very close to us, so they are easy to study d.) they have a regular shape, but it is so complicated it was hard to figure out
c
Our Milky Way Galaxy is what type of galaxy? a.) Elliptical b.) Irregular c.) Spiral d.) Dwarf Elliptical
c
Which of the following statements about the implications of Hubble's Law is FALSE? a.) the law implies that the whole universe must be expanding b.) the law can be used to measure distances to remote galaxies for which we can measure a Doppler shift c.) 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 d.) the law does NOT require us to be at the center of the expanding universe e.) although galaxies move away from each other, they themselves are not expanding in size
c
Which type of galaxy is observed to contain mostly older stars? a.) Spiral b.) Irregular c.) Elliptical
c
Why is the use of Hubble's Law to measure distances to galaxies so important to astronomers? a.) It's stretching the truth to say that Hubble's Law is a really important way to get distances to galaxies; really, it's no more important than any other method b.) Many galaxies don't move away from us, so when we find one that does, it's really a big deal c.) The other ways of getting distances only work for really far away galaxies; so the Hubble Law is the only way to measure distances to nearby galaxies d.) Most galaxies are so far away, the only way to get distances to them is to use Hubble's Law
d
An astronomer discovers a massive galaxy which has four nuclei. What is a likely explanation for a galaxy having more than one nucleus? a.) the nuclei of galaxies often split into two or more parts because of internal activity b.) the galaxy must have been a quasar earlier in its life c.) astronomers have no explanation for multiple nuclei in galaxies; it's baffling d.) the galaxy must have had an unusual number of supernova explosions e.) the galaxy must have swallowed several smaller galaxies that were its neighbors
e
If we want to see what galaxies looked like at a time close to the beginning of the universe, where should we look? a.) in the Local Group of galaxies b.) within the nearest 100 million light years from the Milky Way c.) it doesn't matter; you can look at any galaxy, because all galaxies look pretty much the same today as they did in the early days of the universe d.) near the center of the Virgo Cluster of galaxies e.) in a direction away from the plane of the Milky Way, where we can see very faint galaxies that are more than 10 billion light years away
e
If you wanted to write a complete "cosmic address" for yourself, including every location or structure you live in, which of the following would NOT be part of that address? a.) The Solar System b.) Earth c.) The Local Group d.) The Milky Way e.) the Coma Cluster
e
The Andromeda Galaxy (our nearest spiral neighbor) has spectral lines that show a blue shift. From this we may conclude that: a.) the universe is no longer expanding b.) this particular nearby galaxy is moving away from us c.) this galaxy has merged with the Milky Way and is now part of it d.) this galaxy has an unusual number of very bright and hot O-type stars in it e.) this particular nearby galaxy is moving toward us
e
Why do galaxies collide, while stars almost never do? a.) stars have a very strong negative charge on them, so they repel other stars that get near b.) stars don't have very much mass, so their gravity is very small and can't pull things well c.) stars are surrounded by planets, which prevent collisions; galaxies are not d.) actually, stars collide all the time, but astronomers don't have any way of observing it e.) stars are much further apart (compared to how big they are) than galaxies are
e