astr 150 exam 4
Based on recent survey, scientists have estimated that what fraction of Sun-like stars have Earth-sized planets in their habitable zones? A. 22% B. 33% C. 10% D. 1% E. 5%
A. 22%
What is a rich cluster of galaxies? A. A cluster containing thousands of galaxies B. A cluster (like our Local Group) that contains at least two large galaxies C. A cluster with more spiral galaxies than ellipticals D. A cluster with a high metal content
A. A cluster containing thousands of galaxies
By what method are most extrasolar planets discovered? A. By observing a star's light dim slightly when the planet passes in front of the star B. By observing the "tug" of the planet's gravity on the star C. By sending space probes to distant stars to survey them for planetary systems. D. By observing a brightening of a star's light when a planet passed in front of it and its gravity bends the star's light, focusing its intensity toward Earth. E. Direct imaging of the planet itself
A. By observing a star's light dim slightly when the planet passes in front of the star
What is the likely fate of our Milky Way within about the next 6-8 billion years? A. It will collide with the Andromeda Galaxy, triggering new star birth in gas and dust clouds. B. It will slowly condense under the action of the central supermassive black hole, causing its spin rate to increase. C. Its rate of rotation will slow and its spiral arms will dissipate into intergalactic space as the galaxy becomes an elliptical galaxy. D. It will continue to move away from its near neighbor galaxy, M31 in Andromeda, allowing its spiral arms to straighten to form a central bar.
A. It will collide with the Andromeda Galaxy, triggering new star birth in gas and dust clouds.
Probably the most difficult factor to estimate in the Drake Equation is A. L, the lifetime of a technologically advanced civilization B. 𝑛𝑒, the number of planets per solar system that are Earthlike (suitable for life) C. 𝑓𝑝, the fraction of stars that have planets D. 𝑓𝑙, the fraction of Earthlike planets on which life actually arises E. 𝑅∗, the rate at which stars form in the galaxy
A. L, the lifetime of a technologically advanced civilization
The first successful detection of interpretable signals from extraterrestrial civilizations was accomplished in which year? A. Never—no such signals have been detected as yet. B. 1997 C. 2001 D. 2010 E. 1960
A. Never—no such signals have been detected as yet.
Quasars are typically observed at very high redshifts. What does this indicate about quasars? A. Quasars occurred in the past. B. Quasars are very luminous. C. Quasars are moving rapidly away from the Milky Way through space. D. Quasars only occur in distant parts of the Universe.
A. Quasars occurred in the past. When we see extremely distant objects, we are seeing them as they were long ago.
What is the idea of panspermia for how life started on Earth? A. That life was transported from space. B. That life started by pure chance. C. That the most extreme life currently on Earth are the first organisms. D. That life was formed around underwater sea vents. E. That life started in the frying pan of life (i.e. hot primordial pools).
A. That life was transported from space.
Based on recent surveys, how many stars have planets? A. The vast majority of stars appear to harbor planets B. About half of all stars have planets C. Only a very few stars, like our Sun, have planets D. Less than half of stars have planets
A. The vast majority of stars appear to harbor planets
What made astronomers who discovered the first quasars realize that they were extremely distant objects? A. Their spectra were highly redshifted. B. They were powerful sources of radio emission. C. They were easily detectable at both visible and radio wavelengths. D. Their spectra contained a number of bright emission lines.
A. Their spectra were highly redshifted. When astronomers first discovered quasars, they noticed that they had spectral lines that were far from where they expected them. They realized that these spectral lines were highly redshifted, indicating that quasars appear to be moving at very high speeds away from us, which means that they are very distant objects.
Why are spiral arms bright? A. because they contain more hot young stars than other parts of the disk B. because they contain far more stars than other parts of the galactic disk C. because they are the only places where we find stars within the disk of the galaxy D. because they contain more molecular clouds than other parts of the disk
A. because they contain more hot young stars than other parts of the disk
What type of galaxy do we usually find at the centers of large galaxy clusters? A. elliptical B. spiral C. irregular D. barred spiral
A. elliptical When observing large clusters of galaxies, astronomers typically find giant elliptical galaxies at their centers. This is most likely because, within large galactic clusters, collisions between galaxies are likely to occur. Not only will this increase the size of the galaxy, but it will also destroy any spiral structure that a galaxy may have had as well as use up any gas and dust, forcing them to form new stars. The result would be a giant elliptical galaxy.
Quasars A. increase in number as redshift increases, a relationship which persists to the highest redshifts we can measure. B. are rare in the Local Group, with only one or two examples. C. are extinct. D. are more common in nearby clusters of galaxies and less common in distant clusters of galaxies.
A. increase in number as redshift increases, a relationship which persists to the highest redshifts we can measure.
The Drake equation can be used to estimate the likelihood A. that we can detect a signal from a technologically advanced civilization. B. that primitive life developed by chance on Earth. C. that extraterrestrial life has visited our planet in the past. D. that life of any kind has developed on another planet in our solar system.
A. that we can detect a signal from a technologically advanced civilization. The Drake equation was designed as a way to estimate the number of technologically advanced civilizations in our Galaxy at any one time. In theory, the more civilizations there are,the greater the chance that we will detect some sort of signal from at least one of them.
The Drake equation attempts to predict A. the number of technologically advanced civilizations in our galaxy. B. the probability that primitive life exists elsewhere in our galaxy. C. the number of inhabitable planets around stars in our galaxy. D. the number of intelligent civilizations in the universe.
A. the number of technologically advanced civilizations in our galaxy.
Scientists are now targeting Europa, one of Jupiter's moons, as a likely site for searching for elementary life-forms because A. there is strong evidence for liquid water beneath the thick ice layer on its surface. B. changes have been seen in the dark lines crossing the icy surface which have a spectral signature of vegetation. C. there appears to be large amounts of dark organic material spread on its surface. D. radio signals that follow a recognizable pattern have been detected from this moon.
A. there is strong evidence for liquid water beneath the thick ice layer on its surface.
The fact that quasars vary on small time scales tells us that A. they are very small B. they are extremely luminous C. they are extremely hot D. they are very massive
A. they are very small If an object varies in its energy output, that variation will be spread out due to the finite size of the object. The bigger the object, the greater the period over which it will be spread out. The fact that quasars vary on small time scales therefore tells us that they must be very small objects.
An astronomer studying the spectrum of a distant galaxy finds that its recessional velocity is 13,200 km/s. What is the distance to the galaxy? Take Hubble's constant to be 22 km/s/Mly. A. 290,400 Mly B. 600 Mly C. 1,667 Mly D. 60,000 Mly
B. 600 Mly
What is the basic shape of a spiral galaxy? A. Approximately spherical with long lanes of dark dust clouds curving through it in a spiral pattern B. A round, flat disk with long lanes of stars that curve outward from a round, nuclear bulge C. A round, flat disk with long lanes of stars that curve outward right from the center of the galaxy D. A round, thin disk of uniform brightness with its edges bent up and down into a spiral shape
B. A round, flat disk with long lanes of stars that curve outward from a round, nuclear bulge
How are galaxies spread throughout the universe? A. They are grouped into clusters that are spread more or less evenly throughout the universe. B. Clusters of galaxies exist that are themselves often clustered into superclusters. Clusters and superclusters appear to be distributed on surfaces surrounding empty regions of space. C. Galaxies are spread more or less evenly throughout the universe. D. Galaxies are densest near the Milky Way Galaxy and become less and less numerous the farther we look out into the universe.
B. Clusters of galaxies exist that are themselves often clustered into superclusters. Clusters and superclusters appear to be distributed on surfaces surrounding empty regions of space.
Why are there no nearby (and thus "young") quasars? A. The immense radiation output from the quasar carries away energy. The mass of the black hole gets smaller until it evaporates. B. Eventually, most of the accretion disk falls into the black hole and the "central engine" runs out of fuel. C. The central black hole eventually consumes the entire galaxy, and with no more matter in the vicinity, it becomes dormant until another galaxy happens to pass nearby. D. The continual infall of material causes the mass of the black hole to grow until it explodes, resulting in a supernova.
B. Eventually, most of the accretion disk falls into the black hole and the "central engine" runs out of fuel.
Why do we find a larger percentage of spiral galaxies in distant clusters compared to nearby clusters? A. Distant clusters are older, and this contrast in the percentage of spirals shows evidence for the natural evolution of ellipticals into spirals. B. Over time, galactic collisions and mergers have destroyed many of the spiral arms which give spirals their distinctive appearance. C. Spirals contain more gas and dust than ellipticals. In older, nearby clusters less gas and dust remain and fewer spirals are created. D. Distant clusters are younger, and this contrast in the percentage of spirals shows evidence for the natural evolution of spirals into ellipticals.
B. Over time, galactic collisions and mergers have destroyed many of the spiral arms which give spirals their distinctive appearance.
Around which types of stars are we most likely to find planets supporting our kind of life forms? A. red giant stars B. Sun-like main-sequence stars C. very low-mass red dwarf stars D. high-mass main-sequence stars
B. Sun-like main-sequence stars
Which of the following phenomena are not thought to be results of collisions or other interactions between galaxies? A. Starbursts. B. The fact that spiral galaxies have both disk and halo components. C. The fact that elliptical galaxies are more common in clusters of galaxies than outside clusters. D. The presence of very large, central dominant galaxies in clusters of galaxies
B. The fact that spiral galaxies have both disk and halo components.
What is believed to be the origin of giant elliptical galaxies? A. Collisions between galaxies in the cluster produce a smooth distribution of stars throughout the cluster; these sink by gravity to the cluster center and form giant elliptical galaxies. B. They grew by devouring smaller galaxies in galactic cannibalism. C. They have grown continuously since their formation, by accreting intergalactic gas. D. They formed that way and have remained unchanged ever since.
B. They grew by devouring smaller galaxies in galactic cannibalism.
The earliest evidence for life on Earth dates to A. about 570 million years ago. B. about 3.8-4.3 billion years ago. C. about 2 billion years ago. D. about 65 million years ago.
B. about 3.8-4.3 billion years ago.
Which observations of quasars convinced astronomers that they were very distant objects? A. They appeared as pointlike star images under the highest magnification, meaning that they must be very far away. B. extreme redshift of hydrogen emission lines, indicating high recessional velocities and hence, by the Hubble Law, very large distances C. their extremely red spectrum, reddened by extreme interstellar absorption of the blue part of the spectrum, meaning that the source must be very far away D. their extreme faintness at visible wavelengths, the inverse square law for visible light showing that they must be very distant
B. extreme redshift of hydrogen emission lines, indicating high recessional velocities and hence, by the Hubble Law, very large distances
Our Galaxy is A. one member of a medium-sized cluster of hundreds of galaxies. B. one member of a small cluster of galaxies. C. one member of a large cluster of thousands of galaxies. D. an isolated galaxy, not a member of any cluster.
B. one member of a small cluster of galaxies.
The fact that we find O and B stars in the disk of our Galaxy but not the halo suggests that A. halo stars have a higher metal content than disk stars. B. star formation still occurs in the disk, but not the halo. C. only low-mass stars formed in the halo. D. dust blocks our view of these stars in the halo.
B. star formation still occurs in the disk, but not the halo. O and B stars are short-lived stars. Finding them in the disk of our Galaxy tells us that our disk is still producing new stars. The lack of O and B stars in the halo tells us that new stars are not being formed there.
Which of the following is evidence that the formation process of our Galaxy may have included collisions with smaller neighbor galaxies? A. the observation that globular cluster are arranged in a spherical "halo" around the Galaxy B. the observation of long moving streams of stars that continue to orbit through our Galaxy's halo C. the presence of millions of new stars, recently formed from clouds of gas and dust D. the existence of supernova remnants, such as the Crab Nebula, in the Galaxy's disk E. the observation that objects outside the orbit of the Sun are moving around the Galaxy faster than we expected
B. the observation of long moving streams of stars that continue to orbit through our Galaxy's halo
Most stars in the Milky Way's halo are ________. A. blue or white in color B. very old C. very young D. found inside molecular clouds
B. very old
If a quasar with a luminosity of 10^12 LSun requires 1 MSun per year, how much mass would a 10^13 LSun quasar require per year? A. 0.1 MSun B. 10^13 MSun C. 10 MSun D. 3.2 MSun E. 100 MSun
C. 10 MSun The energy generated scales with the input mass, so inputing 10 times more energy results in 10 times more energy output.
Suppose that a particular galaxy is 400 million light-years (Mly) from Earth. What is the recessional velocity of this galaxy? Take Hubble's constant to be 22 km/s/Mly. A. 18.2 km/s B. 880 km/s C. 8,800 km/s D. 55,000 km/s
C. 8,800 km/s
What type of galaxy will likely be the result from the merger of the Milky Way and Andromeda? A. A spiral galaxy, but with twice as many arms. B. A barred spiral galaxy, like the Milky Way today, but with a much larger bulge. C. An elliptical galaxy D. They will be utterly destroyed, with most of the material falling into the merged supermassive black holes.
C. An elliptical galaxy When the Milky Way and Andromeda merge, it will destroy any spiral structure that the galaxies may have had as well as use up any gas and dust, forcing them to form newstars. The result will be an elliptical galaxy.
Why do we think extraterrestrial life would likely be carbon-based? A. Only carbon can form up to 4-bonds at a time with other atoms. B. Only carbon chemicals can dissolve in water. C. Carbon has real, significant advantages over alternatives like silicon. D. It is just a pro-carbon bias. Other chemistries are just as good as carbon.
C. Carbon has real, significant advantages over alternatives like silicon.
In which of the following type of galaxy is star formation no longer occurring? A. Irregular galaxies B. Barred spiral galaxies C. Elliptical galaxies D. Spiral galaxies
C. Elliptical galaxies
On the surface of which planet or moon in our planetary system have experiments been carried out to search for life-forms or evidence of life? A. Jupiter's moon, Europa B. Jupiter C. Mars D. Venus
C. Mars
How often do stars form in our galaxy, on average? A. On average, one star forms per thousand years. B. We cannot yet answer this question. C. On average, 2-3 stars form per year. D. Hundreds of stars form per year. E. The Milky Way produces about 20-30 new stars per year.
C. On average, 2-3 stars form per year.
If an alien bacteria or virus lands on Earth it is unlikely to be seriously dangerous to humans why? A. It is totally impossible for alien bacteria or viruses to land on Earth. B. They are too little to make any difference. C. Terrestrial bacteria or viruses have evolved to become dangerous to humans. D. Fermi's Paradox proves that ET life can not exist. E. No hands. No ray guns.
C. Terrestrial bacteria or viruses have evolved to become dangerous to humans.
One of the consequences of the collision of two galaxies appears to be A. almost nothing, because stars are widely separated in each galaxy and the probability of star-to-star collisions is very small. B. a very large explosion, similar to but much larger than a supernova. C. a burst of vigorous star birth. D. the disappearance of one of the galaxies into the central supermassive black hole of the other.
C. a burst of vigorous star birth.
The Milky Way Galaxy is a(n) A. elliptical galaxy B. spiral galaxy (no bar) C. barred spiral galaxy D. irregular galaxy
C. barred spiral galaxy
The source of the hot, intergalactic gas in many rich, regular clusters of galaxies appears to be A. supernovae (exploding stars). B. jets of gas ejected by supermassive black holes at the centers of the galaxies. C. collisions between galaxies in the cluster. D. bursts of star formation in merging galaxies.
C. collisions between galaxies in the cluster.
Evidence obtained over the last few years indicates that quasars are most probably A. evidence of very intense star-building activity in certain distant dust and gas clouds. B. the focused image of a distant galaxy by the gravitational lens effect of a closer galaxy. C. the central nuclei of very distant, very active galaxies. D. the remnant cores of exploding stars or supernovae.
C. the central nuclei of very distant, very active galaxies.
The Hubble Law, representing observations of distant galaxies in the universe, relates which two parameters? A. the mass of a distant galaxy and its recession velocity B. the mass of a distant galaxy and its luminosity C. the distance to a distant galaxy and its recession velocity D. the luminosity of a distant galaxy and the width of the 21-cm radio line of hydrogen
C. the distance to a distant galaxy and its recession velocity
Which of the following is evidence that the formation process of our Galaxy may have included collisions with smaller neighbor galaxies? A. the observation that globular clusters are arranged in a spherical "halo" around the Galaxy B. the observation that objects outside the orbit of the Sun are moving around the Galaxy faster than we expected C. the observation of long moving streams of stars that continue to orbit through our Galaxy's halo D. the existence of supernova remnants, such as the Crab Nebula, in the Galaxy's disk E. the presence of millions of new stars, recently formed from clouds of gas and dust
C. the observation of long moving streams of stars that continue to orbit through our Galaxy's halo
What observational fact convinces astronomers that the source of energy in a typical quasar is physically very small? A. the appearance of all quasars as starlike objects in our sky B. the extreme distance of all quasars C. the rapid variation of the intensity of the source D. the extremely high redshift of its spectrum
C. the rapid variation of the intensity of the source
What defines the habitable zone around a star? A. the region around a star where the ultraviolet radiation does not destroy organisms on a planetary surface B. the region around a star where rocky planets form C. the region around a star where liquid water can potentially exist on planetary surfaces D. the region around a star where life exists E. the region around a star where humans can survive
C. the region around a star where liquid water can potentially exist on planetary surfaces
Suppose that galaxy was active as a 10^13 LSun quasar for 10^8 years (i.e., 100 million years). How large would the black hole grow? A. 10^8 MSun B. 10^10 MSun C. 10^12 MSun D. 10^9 MSun E. 10^11 MSun
D. 10^9 MSun 10 MSun/yr × 10^8 yrs = 10^9 MSun
How many planets outside of our solar system have we discovered? A. About 400 B. None so far. C. millions D. About 4000 E. About 40,000
D. About 4000
What type of galaxy are more likely to find at the center of a rich cluster of galaxies? A. Barred spiral galaxy B. Spiral galaxy C. Irregular galaxy D. Elliptical galaxy
D. Elliptical galaxy
What does the Fermi Paradox say? A. Given the size of the Galaxy, there should be an exact duplicate of the Earth somewhere and we should have found it B. If life on Earth took a miracle to form, then there should be no life anywhere else C. If all the planets in our solar system besides Earth are lifeless, then it must follow that most of the planets around other stars are also lifeless and finding life is hopeless D. Given all the time since the Big Bang and all the stars, why has some form of intelligent life in the Galaxy not established a network throughout the Galaxy and visited us? E. When Fermi got ill, he always needed two doctors to diagnose him
D. Given all the time since the Big Bang and all the stars, why has some form of intelligent life in the Galaxy not established a network throughout the Galaxy and visited us?
What is the greatest threat to life on Earth during a galactic collision? A. A star from the other galaxy colliding with Earth. B. A rogue black hole passing through the solar system. C. Falling into the supermassive black hole at the center of the Galaxy. D. Passing through a starburst region with its intense UV light and frequent supernovae.
D. Passing through a starburst region with its intense UV light and frequent supernovae.
What evidence supports the existence of a black hole at the center of our galaxy? A. We observe an extremely bright X-ray source at the center of our galaxy. B. We observe a large, dark object that absorbs all light at the center of our galaxy. C. We can see gas falling into an accretion disk and past the event horizon of a black hole. D. The motions of the gas and stars at the center indicate that it contains 4.1 million solar masses within a region as small as the solar system.
D. The motions of the gas and stars at the center indicate that it contains 4.1 million solar masses within a region as small as the solar system.
If there are other civilizations at present in the Milky Way Galaxy, which statement is almost undoubtedly true? A. They have social structures that are completely different from our own; for example, different types of "family" units, and so on. B. For fun, they enjoy "buzzing" to Earth and temporarily abducting people, showing a clear preference for people located in less-developed rural areas. C. They are anatomically much like us, with two arms, two legs, two eyes, and two ears. D. They are far more technologically advanced than we are.
D. They are far more technologically advanced than we are.
When galaxies collide, what happens in general to the stars contained within them? A. They collide head-on with stars in the other galaxy, forming larger stars. B. They are captured in large numbers within the supermassive black holes at the centers of each galaxy. C. They merge into one galaxy, leaving the other one relatively underpopulated. D. They mostly pass by the stars in the other galaxy without colliding. E. They get dimmer due to obscuration by gas and dust in the other galaxy.
D. They mostly pass by the stars in the other galaxy without colliding. Since galaxies are a collection of objects, a collision between galaxies does notmean a physical collision between the objects within them. Galactic collisions involve the two galaxies passing through each other, gravitationally distorting the shapes of the galaxies and the orbits of the stars within them. The distances between the stars, though, are so large that it is extremely unlikely that they will collide.
Detailed measurements of the disk suggest that our Milky Way is A. a globular cluster. B. an irregular galaxy. C. a spiral galaxy. D. a barred spiral galaxy. E. an elliptical galaxy.
D. a barred spiral galaxy. Measurements of stellar motion in and near the bulge imply that it is football shaped, about half as wide as it is long, characteristic of a barred spiral galaxy.
The "central engine" of an active galaxy appears to be A. stars falling into a supermassive black hole, their remnants being thrown out in all directions. B. supernova explosions in an extremely dense star cluster at the center of the galaxy. C. the violent merger of two galaxies, in which the collision throws out jets of matter along the rotation axis of the larger galaxy. D. a supermassive black hole at the center of an accretion disk, with jets of material being ejected perpendicular to the disk.
D. a supermassive black hole at the center of an accretion disk, with jets of material being ejected perpendicular to the disk.
High speed motion of gas and stars near the Milky Way Galaxy's center is explained by A. gamma-ray bursts. B. accretion disks around neutron stars. C. tidal forces from the Andromeda Galaxy. D. a supermassive black hole. E. gravitation from globular clusters.
D. a supermassive black hole. Recent observations estimate the black hole to be 4.6 million solar masses.
Terrestrial organisms have been found in water that is A. boiling hot. B. fiercely acidic. C. amazingly salty. D. all of the above.
D. all of the above.
What are the building blocks of life? A. helium, neon, argon, krypton B. hydrogen, helium, lithium, beryllium C. carbon, iron, oxygen, sulfur D. hydrogen, oxygen, nitrogen, carbon E. carbon, calcium, iron, phosphorus
D. hydrogen, oxygen, nitrogen, carbon
The Sun's location in the Milky Way Galaxy is ________. A. in the halo of the galaxy, about 26,000 light-years above the galactic disk B. at the very outer edge of the galactic disk C. very near the galactic center D. in the galactic disk, roughly halfway between the center and the outer edge of the disk
D. in the galactic disk, roughly halfway between the center and the outer edge of the disk
According to Hubble's law, as the distance between galaxies __________ the __________ increases. A. decreases; apparent recessional velocity B. increases; apparent brightness C. decreases; apparent brightness D. increases; apparent recessional velocity
D. increases; apparent recessional velocity Hubble's law is a direct relationship between the rate at which galaxies appear to be moving away from us and their distance from us. The farther away a galaxy is, the faster it appears to be moving away from us. This relationship only applies on large scales; it does not apply to nearby galaxies whose motions are dominated by gravitational forces.
The fact that quasars can be detected from distances where even the biggest and most luminous galaxies cannot be seen means that A. they must be in directions where intergalactic absorption by dark matter is minimum, allowing us to see them. B. they have not been as redshifted by their motion as have galaxies, and hence they can still be seen. C. they must be in directions where gravitational focusing by the masses of nearer galaxies makes them visible from Earth. D. they must be intrinsically far more luminous than the brightest galaxies.
D. they must be intrinsically far more luminous than the brightest galaxies.
Quasars appear to be A. very distant, intrinsically faint objects, moving toward Earth very rapidly. B. very distant and intrinsically bright objects moving in random directions at high speeds. C. relatively close, very bright objects moving away from Earth. D. very distant, intrinsically bright objects, moving away from Earth at very high speeds.
D. very distant, intrinsically bright objects, moving away from Earth at very high speeds.
What is the diameter of the disk of the Milky Way? A. 1,000,000 light years B. 100 light years C. 10,000 light years D. 1,000 light years E. 100,000 light years
E. 100,000 light years
Of all the potentially deadly phenomena in the Universe, which is most likely to kill YOU? A. Black hole B. Solar flare C. Alien virus D. Supernova/Gamma-ray burst E. Asteroid impact
E. Asteroid impact
For which of the following factors in the Drake Equation do we actually have observational knowledge rather than just a speculative estimate? A. 𝑓𝑝, the fraction of stars with planets B. 𝑅∗, the rate at which stars form in the galaxy C. 𝑓𝑙, the fraction of Earthlike planets on which life actually arises D. 𝑓𝑖, the fraction of planets with life-forms that evolve into intelligent species E. Both 𝑅∗ and 𝑓𝑝
E. Both 𝑅∗ and 𝑓𝑝
Our Sun is located in the Milky Way Galaxy A. in a globular cluster. B. about 26,000 light-years from the center, in the halo. C. in the bulge, near the Orion arm. D. at the outer edge of the Galactic disk, in the plane. E. about half-way from the center, in the disk.
E. about half-way from the center, in the disk.
Where does most star formation occur in the Milky Way today? A. in the halo B. in the bulge C. in the Galactic center D. everywhere throughout the galactic disk E. in the spiral arms
E. in the spiral arms
Elliptical galaxies appear red because they contain... A. stars of all ages and colors B. mostly old blue stars C. mostly young red stars D. mostly young blue stars E. mostly old red stars
E. mostly old red stars
