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Intro to the Universe - Final Exam
Terms in this set (77)
Astronomers determined how stars evolve over time by observing individual stars
(d) at different stages of evolution and figuring out how stars evolve from one stage to the next
Which of the following stars are typically found near emission nebulae
(e) O stars
Reflection nebulae are blue and emission nebulae are red becasue
(d) reflection nebulae scatter blue light and emission nebulae emit red light
Star formatin most likely occurs in which of the following types of nebulae?
(a) dark nebulae
Compared with our Sun, which of the following does NOT describe the protostar out of which it formed?
(d) all of the above statements describe the protostar
It is unlikely that you'll ever observe a protostar in the night sky because
(c) they are enshrouded by dust that blocks visible light
Which of the following will NOT trigger star formation?
(b) high-speed winds from K and M stars slam into surrounding clouds
Studying star clusters is useful because we can assume that all of the stars have the same
As a star evolves over time, which of the following occurs?
(b) its size increases
Which stars can fuse all of their hydrogen, not just the hydrogen in their core?
(a) low-mass stars (less than 0.4 solar masses)
Metal-poor stars tend to be among the __________ stars.
Which property of a star controls its formation, evolution, and demise?
Once the core of a star ends hydrogen fusion, the core __________ in size and __________ in temperature.
(c) decreases; increases
At certain times in its evolution, a star undergoes shell fusion. This causes the outer layers to __________ in size, __________ in temperature, and __________ in luminosity.
(b) increase; decrease; increase
Red giant stars are composed mostly of
If a star's core were to suddenly start making less energy than normal, the following chain of reactions would occur: The star's pressure would __________, which would cause the star to __________, which would cause the temperature in the star's core to __________, which would return the energy production rate to its normal level.
(e) decrease; contract; increase
Planetary nebulae are mostly composed of
White dwarfs resist gravitational collapse through
(c) degenerate-electron pressure
As a white dwarf cools over time, its size
(b) stays the same
Stars that fuse helium but no heavier elements are
(b) between 0.4 M⨀ and 4 M⨀
The end state of a low mass star like our sun is
(b) a white dwarf
A star on the asymptotic giant branch is undergoing
(d) shell helium fusion and shell hydrogen fusion
A white dwarf is composed of
(d) both b and c
Our sun will end its life as a
(d) white dwarf
Why does it take a 25-solar-mass star roughly 600 years for carbon fusion to occur in its core, but only 1 day for silicon fusion to occur?
(a) temperatures and pressures are much higher by the time the star undergoes core silicon fusion.
The most massive stars end all fusion with a core composed of
Why do massive stars end their fusion with iron?
(c) fusion beyond iron does not produce a net energy
A massive star lives a shorter amount of time than the sun because
(b) it fuses more hydrogen, but its higher temperature means it fuses faster.
A massive star explodes because
(e) both b and c
After the initial explosion of a massive star, how does a supernova continue to radiate light energy?
(c) unstable elements created in the explosion radioactively decay and emit gamma rays.
The frequency at which we observe supernovae in other galaxies is higher than the frequency at which we observe them in our own. Why is that?
(d) dust in the plane of our Galaxy blocks our view of any supernovae in our Galaxy.
A pulsar is a rapidly rotating
(b) neutron star
Every pulsar is a neutron star. Is every newly formed neutron star a pulsar?
(d) yes, but only when its beam of radiation crosses Earth's path do we detect it as a pulsar.
If the Sun were replaced by a 1-solar-mass black hole, what would happen to its gravitational influence on Earth?
(c) it would stay the same
The event horizon of a black hole is defined as the distance from the black hole at which
(a) light can just barely escape from its gravitational pull.
A black hole has a density of
Why are black holes said to be "black"?
(b) the velocity needed to escape from a black hole is greater than the speed of light, so not even light can escape.
Is it possible to detect low-mass black holes?
(b) yes, by detecting radiation being emitted by gas falling into a black hole.
How do astronomers theorize that a supermassive black hole formed in the center of our Galaxy?
(d) when our Galaxy first formed, some of the gas immediately collapsed directly into a supermassive black hole.
What happens if the mass of a white dwarf is pushed above 1.4 solar masses?
(b) it explodes as a Type I supernova
What is the main observational difference between a Type I and Type II supernova?
(a) spectra of Type I supernovae lack hydrogen lines while spectra of Type II supernovae are abundant in hydrogen.
Describe Type Ia and Type II supernovae
(c) type Ia are white dwarfs in binary systems and Type II are massive stars.
Which of the following is NOT one of the differences between novae and X-ray bursters?
(c) novae represent an explosion of surface gases while X-ray bursters represent a core explosion.
Will our Sun ever explode as a nova?
(d) no, it does not exist in a binary system
In general, spiral galaxies with a greater percentage of gas and dust have __________ spiral arms and __________ central bulges.
(d) narrower; smaller
The main difference between normal spirals and barred spirals is the
(d) shape of the central bulge
The difference between E0 galaxies and E7 galaxies is that E7 galaxies are __________ than E0 galaxies.
(c) more elliptical
Why do elliptical galaxies tend to appear reddish in color?
(d) they are composed mostly of old stars that are characteristically red.
Which of the following is NOT a difference between spiral and elliptical galaxies?
(b) spiral galaxies are younger, whereas elliptical galaxies are older.
Which of the following could NOT be how galaxies evolve?
(a) elliptical galaxies collapse to a disk and turn into spiral galaxies.
The galaxies with the least amount of gas and dust are
What is the best distance indicator to find the distance to the Andromeda galaxy?
(b) cepheid variables
If Cepheid variable stars were actually more luminous than originally thought, how would this affect our measurements of distances to galaxies with Type Ia supernovae?
(a) they would be farther than originally calculated.
When galaxies collide, what happens in general to the stars contained within them?
(b) they mostly pass by the stars in the other galaxy without colliding.
We know that dark matter exists in galaxy clusters because galaxies within clusters
(d) are moving faster than expected.
Which is NOT easily explainable as interactions between galaxies?
(b) we see spiral and elliptical galaxies at high redshifts.
What made astronomers who discovered the first quasars realize that they were extremely distant objects?
(c) their spectra were highly redshifted
The fact that many quasars are associated with distorted galaxies suggests that
(b) galactic collisions can trigger the process that causes a galaxy's center to emit so much energy.
The fact that active galactic nuclei (AGN) vary on small time scales tells us that
(b) they are very small.
What leads astronomers to believe that quasars are powered by supermassive black holes?
(c) only material accreting onto a supermassive black hole can account for their energy output.
Active galaxies get their extremely high luminosities from
(a) accretion onto a supermassive black hole.
Which of the following does NOT describe how galaxies appeared 11 billion years ago?
(b) they were redder than galaxies are today.
If the development of life requires the presence of metals in a solar system, which type of galaxy is least likely to contain life?
According to Olbers's paradox, the fact that the night sky is dark tells us that our observable universe is not
(b) static and infinite.
According to Hubble's law, as the distance between galaxies __________ the __________ increases.
(b) increases; apparent recessional velocity
The value of Hubble's constant is important because it can be used to determine all of the following, EXCEPT
(c) the size of the largest structures formed in the early universe.
Where is the center of our universe?
(e) there is no center to our universe.
How does a cosmological redshift differ from a Doppler redshift?
(c) a cosmological redshift is due to the expansion of space while a Doppler redshift is due to motion through space.
Relative to Earth, the motion of nearby galaxies is controlled by __________ and the motion of distant galaxies is controlled by __________.
(b) gravity; the Hubble flow
If the value for Hubble's constant was larger than determined, then the calculated age of our universe would be
The cosmic background radiation is
(a) leftover radiation from the Big Bang redshifted to longer wavelengths.
Why are the first photons that we detect from a time roughly 380,000 years after the Big Bang?
(b) before this time, free electrons absorbed and scattered any photons, preventing them from moving through the universe.
Evidence that the universe underwent a period of rapid inflation includes the fact that
(b) the cosmic microwave background (CMB) is extremely uniform.
The cosmic microwave background (CMB)
(a) was predicted by the Big Bang theory.
When looking at the cosmic microwave background (CMB), astronomers see
(d) all of the above are seen in the CMB.
Why can't we observe an infinite universe?
(d) all of the above are reasons why we cannot observe an infinite universe.
Which of the for fundamental forces of nature is weakest?
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