Astro 102 - Final Exam Set Questions With 100% Correct Answers | Latest Update
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Course
ASTR 102
Institution
ASTR 102
Astro 102 - Final Exam Set
Questions With 100% Correct
Answers | Latest Update
What is cosmology? - ANSWER : the study of how the
distribution of galaxies changes over time
How does the size of a supernova compare with the size
of the observable universe? - ANSWER : The size of a
super...
Astro 102 - Final Exam Set
Questions With 100% Correct
Answers | Latest Update
What is cosmology? - ANSWER ✔ : the study of how the
distribution of galaxies changes over time
How does the size of a supernova compare with the size
of the observable universe? - ANSWER ✔ : The size of a
supernova is 2/3 the size of the observable universe
Cepheids with longer periods have... - ANSWER ✔ :
higher luminosities
A Cepheid with a period of 30 days has an average
luminosity that is.... - ANSWER ✔ : 10, 000 times the
luminosity of the Sun
The greater the luminosity of a Cepheid star, - ANSWER
✔ : the larger its radius
What are the steps that describe how we use Cepheids
as a tool to make cosmic distance measurements? -
ANSWER ✔ : Step 1: Measure the period of the
Cepheid's brightness variations
Step 2: Use the period-luminosity relation to determine the
Cepheid's luminosity
,Step 3: Calculate the Cepheid's distance from its
luminosity and apparent brightness
What baseline distance must we know before we
measure a parallax? - ANSWER ✔ : the Earth-Sun
distance
What cosmic distance measurement techniques are
considered "standard candle" techniques? - ANSWER ✔ :
Cepheids, white dwarf supernovae (distant standards) and
main sequence fitting
* You are using the luminosity of these objects
What would happen if Cepheids did not exist and there
were no other standard candle technique that worked at
the same distances? - ANSWER ✔ : We would not be
able to measure the distances of distant galaxies
Why do we use Hubble's law to estimate the distances of
most distant galaxies, rather than using white dwarf
supernovae in all cases? - ANSWER ✔ : We have not
observed white dwarf supernovae in most gaalxies
Which technique is the most useful for measuring the
distance to a galaxy located 10 million light-years away? -
ANSWER ✔ : Cepheids
Rank the diagrams based on how much the galaxy has
expanded in size - ANSWER ✔ : The universe as a
whole is expanding, but gravitational bound objects such
,as galaxies are not expanding, so the diagrams would we
ranked equally.
How are speed and distance correlated when it comes to
galaxies? - ANSWER ✔ : The further you are, the faster
your speed
* This is Hubble's law
Which evidence supports that the universe is expanding?
- ANSWER ✔ : 1. All galaxies in to Coma cluster of
galaxies have redshifted spectra
2. The measured rate of expansion is the same in all
directions
3. Galaxies 200 million light-years away move away from
us twice as fast as galaxies 100 million light-years away
Which evidence contradicts that the universe is
expanding? - ANSWER ✔ : 1. Spiral galaxies move away
from us 10% faster than elliptical galaxies at the same
distances
2. Irregular galaxies outside the Local Group are moving
toward us
Why is the observation that "irregular galaxies outside the
local toward us" contradict that the universe is expanding?
- ANSWER ✔ : Because Hubble's law predicts that all
galaxies outside our Local group should be moving away
from us
, Why does the observation "The Andromeda galaxy, a
member of our local group, is moving toward us" NOT
contradict the idea that the universe is expanding? -
ANSWER ✔ : Because the galaxies of the local group are
gravitationally bound together. In other words, the
universe expands, not its galaxies
We can measure the expansion rate by studying galaxies
in many different directions in space and at different times
of year. If we compare such observations, we would find
that the expansion rate is - ANSWER ✔ : the same no
matter when or in which direction we measure it.
Which of the following is an important starting assumption
of galaxy formation? - ANSWER ✔ : Some regions in the
universe start out denser than others
Properties of an elliptical galaxy? - ANSWER ✔ : 1.
Protogalactic cloud has high density
2. Stars form rapidly as the protogalactic cloud shrinks
3. A galaxy collision strips away gas
3. Protogalactic clouds rotate very slowly
Properties of a spiral galaxy? - ANSWER ✔ : 1. Most
protogalactic gas settles into a disk
2. Protogalactic cloud has high angular momentum
Suppose a collision strips gas out of a spiral galaxy. Why
would this tend to change the spiral galaxy into an elliptical
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