astronomy exam 3
Please put the following things that astronomers can observe in order of distance from the nearest to the farthest.
(nearest) pluto and its moon charon the center of the Milky Way galaxy the Andromeda galaxy the most distant cepheid astronomers can see the most distant galaxy in which we have seen at Type 1a Supernova (farthest)
Why did Einstein introduce the cosmological constant into the equations of his General Theory of Relativity when describing the universe?
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
How do astronomers know that there aren't significant amounts of dark matter within our solar system?
a lot of dark matter would affect the motions (orbits) of our spacecraft as they move through the solar system, and we see no such effect
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
a new kind of subatomic particle
Which of these is NOT evidence of dark matter? a. Black holes b. Gravitational lensing c. The bullet cluster d. Flat rotation curves of galaxies
a. Black holes
The Milky Way is orbited by (select all that apply) a. Numerous dwarf galaxies b. The Large Magellanic Cloud c. The Small Magellanic Cloud d. The Virgo Cluster e. The moon
a. Numerous dwarf galaxies b. The Large Magellanic Cloud c. The Small Magellanic Cloud
If two straight lines start out parallel but eventually cross, then they must be in a a. Spherical geometry b. Spacetime geometry c. Flat geometry d. Saddle-shaped geometry
a. Spherical geometry
The Milky Way is part of a. The Local Group b. The Tarantula Nebula c. The Solar System d. The Large Magellanic Cloud
a. The Local Group
The stelliferous epoch will end a. in a few 1 trillion years b. in 5 billion years c. 6,000 years d. 1 million years
a. in a few 1 trillion years
The formation of the first stars and quasars marks the transformation of the universe from its smooth initial state (the cosmic microwave background) to its clumpy current state (large scale structure). What important transition in the Universe occurred as a result of these early stars and galaxies having formed and then producing light? a. reionization b. recombination c. nucleosynthesis d. inflation
a. reionization
The cosmic microwave background is a. the glow left over from the birth of the cosmos when the universe was much hotter than it is now b. created by galaxies filling the sky c. produced by matter-anti-matter annihilation between galaxies
a. the glow left over from the birth of the cosmos when the universe was much hotter than it is now
What observational fact is explained by inflation? a. The formation of elliptical galaxies b. The existence of black holes c. The isotropy of our universe d. The primordial abundances of H and He
c. The isotropy of our universe
By examining rich clusters of galaxies, such as the Coma Clusters, astronomers have discovered that spiral galaxies
are found mostly in the outer regions of such clusters, not in the middle
In our modern view of the expansion of the universe, we understand that it is space (or, more precisely, space-time) 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?
as space stretches, the waves of radiation in space also stretch and their wavelength increases
The bullet cluster is the "smoking gun" for the existence of what? a. galaxies b. dark energy c. dark matter d. intergalactic gas
c. dark matter
If the speed of the expansion of the universe is increasing, then compared to what they would look like in a steadily expanding universe, type Ia (white dwarf) supernovae will be a. the same b. brighter c. fainter
c. fainter
The first clear evidence for the existence of dark energy came from a. Hubble's observations of redshifts of nearby galaxies b. particle physics experiments c. observations of distant supernova type Ia (exploding white dwarfs) d. the discovery of the cosmic microwave background
c. observations of distant supernova type Ia (exploding white dwarfs)
What is the order of epochs discussed in this video? a. degenerate era, stelliferous era, black hole era, dark era, primordial era b. primordial era, black hole era, stelliferous era, degenerate era, dark era c. primordial era, stelliferous era, degenerate era, black hole era, dark era d. primordial era, degenerate era, stelliferous era, black hole era, dark era
c. primordial era, stelliferous era, degenerate era, black hole era, dark era
As per Big Bang theory, a. there is sound in space after all b. galaxies are repelling each other c. space between galaxies is expanding, creating the observed redshifted spectra d. we are at the center of an expanding universe
c. space between galaxies is expanding, creating the observed redshifted spectra
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:
carbon
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)
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
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?
inflation increased the size of the universe so much that the resulting universe looks flat from any point of view
According to our modern "bottom-up" model of the formation of large structures in the universe, the structures that formed first were about the mass of a
large globular cluster or a small galaxy
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
less than the critical density
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
Which of the following observations is a convincing argument for the idea that quasars are located inside galaxies?
relatively nearby quasars show "fuzz" around them with the same spectra and redshift as the quasar
When we determine the age of the universe using the Hubble Time, what important simplifying assumption goes into our calculations?
that the expansion of the universe has been happening at the same rate - neither speeding up or slowing down
Which of the following is pretty good evidence that the universe began with a Big Bang?
the 3-degree cosmic microwave background radiation
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
Put the following in order of how abundant they are in the universe (how much of the universe they make up), starting with the least abundant to the most abundant.
(most abundant) dark energy dark matter ordinary matter matter inside stars atoms in livings organisms (least abundant)
Put the following objects in order of distance, from the closest to the furthest away:
(nearest) crab nebula Andromeda galaxy black hole at center of M87 quasar 3C273 (whose red shift indicates it is moving away at 15% speed of light) quasar who's red shift indicates it is moving away at 90% speed of light (farthest)
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?
95%
Dark matter... (select all that apply) a. interacts only by gravity b. emits light c. interacts only through the nuclear force d. interacts only through electro-magnetic force
a. interacts only by gravity
The reciprocal of the Hubble constant (1/H) is a rough measure of the:
the age of the universe
A friend of yours who is a science fiction fan hears you talk about the fact that astronomers now believe that the mechanism for the large energy output of quasars involves a supermassive black hole. He challenges you, saying something like "Oh come on, every science fiction fan knows that nothing, not even light, can escape from a black hole! How can a black hole be an energy source?" How would you respond to his objection?
the energy we see from quasars comes from regions where matter is falling in; these regions are still outside the event horizon
If a very distant galaxy looks blue overall to astronomers, from this they can conclude that:
the galaxy must have a lot of young stars and thus active star formation must still be going in it
With enormous effort, a team of astronomers manages to collect enough light from a galaxy far, far away to produce a spectrum. That spectrum has lines from the elements carbon, silicon, and sulfur. This tells the team that
the galaxy must have had an entire generation of stars that was born, lived, and died
An astronomer discovers a massive galaxy which has four nuclei. What is a likely explanation for a galaxy having more than one nucleus?
the galaxy must have swallowed several smaller galaxies that were its neighbors
How do astronomers explain the energetic jets that come out of quasars and active galactic nuclei in opposite directions?
the jets are "spit out" from the chaotic accretion disks of supermassive black holes in directions that are perpendicular to the disk
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
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
A distant quasar shows a large redshift -- one so large, in fact, that the features we now see in the visible-light region of the spectrum would be invisible to us, were it not for the redshift. What band of the electro-magnetic spectrum were these features most likely in, before the spectrum was redshifted?
ultraviolet
One of the things that our current "standard model" of the Big Bang Theory doesn't explain is
why the temperature of the cosmic microwave background is so uniform throughout all of space
For the first few minutes, the early universe was at temperatures that allowed nuclear ________ to occur, mostly building up deuterium, and then the nuclei of the element ______. After the first few minutes, this process had to stop because the universe was too _______. In addition to the simplest elements made of protons and neutrons, we know that the universe also had to contain ________, but what that is made of, scientists do not yet know. About 380,000 years after the Big Bang, the loose __________ were able to combine with nuclei, and the universe became _________ to electromagnetic radiation. The photons from this era (the "afterglow of the early universe") can still be detected, and were first found by __________. One important way that we know this radiation is from the early universe is that it's ________.
For the first few minutes, the early universe was at temperatures that allowed nuclear FUSION to occur, mostly building up deuterium, and then the nuclei of the element HELIUM. After the first few minutes, this process had to stop because the universe was too COLD. In addition to the simplest elements made of protons and neutrons, we know that the universe also had to contain DARK MATTER, but what that is made of, scientists do not yet know. About 380,000 years after the Big Bang, the loose ELECTRONS were able to combine with nuclei, and the universe became TRANSPARENT to electromagnetic radiation. The photons from this era (the "afterglow of the early universe") can still be detected, and were first found by PENZIAS AND WILSON. One important way that we know this radiation is from the early universe is that it's ISOTROPIC.
Let's say a galaxy has been measured to be receding from us at 19,000 km/sec and we use a Type Ia supernova to measure that it is 950 million LY away from us.
Hubble Constant = 20
In the 1930's ___________ photographed 1283 sample areas of the sky and counted the number of galaxies on his images. From such surveys, he found that the distribution of galaxies is the same in all directions (so that it's __________,) and any sizeable portion looks the same as any other portion (so that it's ______________.) The idea that the universe has these two properties throughout is called the ________________. The Milky Way is part of a small group of galaxies called the ______________. The nearest rich cluster of galaxies is called the ____________. Clusters and groups of galaxies are themselves found in huge _____________, often in the shape of filaments. Separating these are emptier bubbles which astronomers call ______.
In the 1930's EDWIN HUBBLE photographed 1283 sample areas of the sky and counted the number of galaxies on his images. From such surveys, he found that the distribution of galaxies is the same in all directions (so that it's ISOTROPIC,) and any sizeable portion looks the same as any other portion (so that it's HOMOGENOUS.) The idea that the universe has these two properties throughout is called the COSMOLOGICAL PRINCIPLE. The Milky Way is part of a small group of galaxies called the LOCAL GROUP. The nearest rich cluster of galaxies is called the VIRGO CLUSTER. Clusters and groups of galaxies are themselves found in huge SUPERCLUSTERS, often in the shape of filaments. Separating these are emptier bubbles which astronomers call VOIDS.
The astronomer Vesto Silpher at the Lowell Obsertatory was the first to show, in the 1910's, that (except for those in the same group with us) all other galaxies showed a _________ in their spectra. By the 1920's, Edwin Hubble (later assisted by ________________) was able to show this for many more galaxies. They were able to measure the distances to nearby galaxies using ___________. Comparing the two kinds of measurements, they found that the _______ of a galaxy was proportional to its distance, a rule that became known as ____________. This implied that the entire universe was expanding. Today astronomers understand the movement of the galaxies away from each other is a result of _________________.
The astronomer Vesto Silpher at the Lowell Obsertatory was the first to show, in the 1910's, that (except for those in the same group with us) all other galaxies showed a RED-SHIFT in their spectra. By the 1920's, Edwin Hubble (later assisted by MILTON HUMASON) was able to show this for many more galaxies. They were able to measure the distances to nearby galaxies using CEPHID VARIABLE STARS. Comparing the two kinds of measurements, they found that the SPEED of a galaxy was proportional to its distance, a rule that became known as HUBBLE'S LAW. This implied that the entire universe was expanding. Today astronomers understand the movement of the galaxies away from each other is a result of THE STRETCHING (EXPANSION) OF SPACE.
The first person to observe that our galaxy is disk-shaped was ______________. In the 20th century, __________ used the distances and directions of many _________ clusters to map out the Milky Way and show that our solar system was not in the center. Part of the difficulty in observing the Galaxy is that we are in the main disk and there is a lot of ______ in the disk, obscuring our view. Today astronomers have observed the distant regions of the Galaxy and know that near the middle, stars are not confined to the disk but are distributed in __________.
The first person to observe that our galaxy is disk-shaped was WILLIAM HERSCHEL. In the 20th century, HARLOW SHAPLEY used the distances and directions of many GLOBULAR clusters to map out the Milky Way and show that our solar system was not in the center. Part of the difficulty in observing the Galaxy is that we are in the main disk and there is a lot of DUST in the disk, obscuring our view. Today astronomers have observed the distant regions of the Galaxy and know that near the middle, stars are not confined to the disk but are distributed in A CENTRAL BULGE.
The term quasar comes from "quasi-stellar object" - a term referring to the fact that they looked like stars, but their properties were not like those of stars. For example, quasars were first found because they gave off significant amounts of _______ waves, which typical stars did not. Their spectra showed a pattern of lines that at first could not be identified, but then __________ showed that they were the lines of regular elements but just with a high ______. Today we understand that quasars are actually distant _______ with bright centers. Astronomers can tell that the central regions are very small (astronomically speaking) because of their rapid ____________.
The term quasar comes from "quasi-stellar object" - a term referring to the fact that they looked like stars, but their properties were not like those of stars. For example, quasars were first found because they gave off significant amounts of RADIO waves, which typical stars did not. Their spectra showed a pattern of lines that at first could not be identified, but then MAARTEN SCHMIDT showed that they were the lines of regular elements but just with a high RED SHIFT. Today we understand that quasars are actually distant GALAXIES with bright centers. Astronomers can tell that the central regions are very small (astronomically speaking) because of their rapid BRIGHTNESS VARIATIONS.
When astronomers look at the total contents of the universe, including both matter and energy, the largest part of the universe is made up of ______________. The second largest part is made up of ____________. Measurements of Type Ia supernovae have shown that the expansion of the universe is _________. Astronomers were puzzled by how uniform the universe is all over, something that can be seen in the uniformity of the temperature of ______________. One solution to this uniformity problem is that the universe, very early on, underwent a period of ____________.
When astronomers look at the total contents of the universe, including both matter and energy, the largest part of the universe is made up of DARK ENERGY. The second largest part is made up of DARK MATTER. Measurements of Type Ia supernovae have shown that the expansion of the universe is SPEEDING UP. Astronomers were puzzled by how uniform the universe is all over, something that can be seen in the uniformity of the temperature of THE COSMIC MICROWAVE BACKGROUND. One solution to this uniformity problem is that the universe, very early on, underwent a period of RAPID INFLATION.
When two galaxies collide, the stars inside them are not likely to be much affected, because the __________ stars is so large compared to their diameters. However, the _______ of stars and gas can be changed, altering the appearance of the galaxies. Astronomers have determined that such collisions are seen more often in ____________. When two galaxies of roughly equal size collide, astronomers call it a _______ of galaxies; but when a small galaxy collides with a much larger one, the process is called ___________. When a galaxy has a significant amount of its interstellar gas compressed by a collision, leading to the birth of many new stars, astronomers call it a __________ galaxy.
When two galaxies collide, the stars inside them are not likely to be much affected, because the SPACE BETWEEN stars is so large compared to their diameters. However, the ORBITS of stars and gas can be changed, altering the appearance of the galaxies. Astronomers have determined that such collisions are seen more often in DISTANT GALAXIES. When two galaxies of roughly equal size collide, astronomers call it a MERGER of galaxies; but when a small galaxy collides with a much larger one, the process is called GALACTIC CANNABALISM. When a galaxy has a significant amount of its interstellar gas compressed by a collision, leading to the birth of many new stars, astronomers call it a STARBURST galaxy.
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
Fusion in the early Universe created a. Hydrogen and Oxygen, explaining the abundance of water in the Universe b. Hydrogen, Helium, and a little bit of Lithium and radioactive Beryllium c. Uranium. All other elements were created from radioactive decay d. Krypton, explaining the existence of Superman
b. Hydrogen, Helium, and a little bit of Lithium and radioactive Beryllium
During the epoch of Big Bang Nucleosynthesis the universe was a. similar to the present-day universe in many respects b. hot, dense, and opaque c. cool and transparent d. filled with stars and planets
b. hot, dense, and opaque
The epoch of recombination a. is the time when galaxies first formed b. is the time when atoms first formed c. is the time when stars first formed d. is another word for the Big Bang
b. is the time when atoms first formed
We can find supermassive black holes at large distances across the cosmos because a. they are so dark that we can see them as black blotches on the sky b. they are among the brightest objects in the unverse c. we can sense their enormous mass through their gravitational pull on Earth
b. they are among the brightest objects in the unverse
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 toward us c. this galaxy has merged with the Milky Way and is now part of it d. this particular nearby galaxy is moving away from us
b. this particular nearby galaxy is moving toward us
If inflation occurred, then our observable universe is only a tiny portion of the entire universe born in the Big Bang. a. False b. True
b. true
Some astronomers searching for what the mysterious "dark matter" might be made of have pinned their hopes on MACHO's (MAssive Compact Halo Objects). What do they think these MACHO's are?
black holes, brown dwarfs, and white dwarfs in the regions outside the main disk of our Galaxy
What is the major evidence supporting the Big Bang Theory? a. The expansion of the universe b. Big Bang nucleosynthesis (i.e., fusion in the early universe) c. The cosmic microwave background radiation d. All of the above
d. All of the above
Observations of the cosmic microwave background radiation by WMAP are most important for a. showing that there are features analogous to spectral lines in its spectrum, so it is not a perfect blackbody, as we previously thought. b. confirming the expansion of the universe. c. determining that the temperature of the radiation is almost exactly what was pre- dicted by the Big Bang theoretical calculations. d. providing strong evidence in favor of a universe that is almost exactly flat.
d. providing strong evidence in favor of a universe that is almost exactly flat.
One of the consequences of dark energy is that a. Maxwell's theory of electromagnetism must be wrong b. the cosmos must eventually collapse on itself c. Einstein's theory of general relativity must be wrong d. the observable universe is getting smaller
d. the observable universe is getting smaller
The galaxy cluster that is closest to our Local Group of galaxies is the a. Ursa Major cluster b. Peanut cluster c. Coma cluster d. Hercules cluster e. Virgo cluster
e. Virgo cluster
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
Where in space did the expansion of the universe begin?
everywhere at once
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 red shift and using Hubble's Law