Download Sample Final - IUPUI Physics

Final Exam Review
Astronomy 205
Dr. Edward Rhoads
Section 1: Multiple Choice (4 points each)
Note: It is possible for a question to have more than one correct answer. You just have
to pick one of the possible correct answers if that happens. This again comes from my
A105 final.
2. The core of the sun is primarily powered by:
A) the burning of chemical fuel
B) gravitational energy
C) nuclear fusion
D) all of the above
3. What is about the expected lifetime of a 0.8 solar mass star?
• A) 6 billion years
• B) 10 billion years
• C) 16 billion years
• D) a 0.8 solar mass star dies before it gets fully formed
4. We have learned that the sun is made of mostly Hydrogen and Helium by:
A) sending a probe to the sun to carry back a sample
B) the composition of Earth’s atmosphere
C) soil samples on the moon
D) the spectrum of the sun
5. While a star is considered a Main Sequence Star it does what?
A) shrink
B) fuse hydrogen into helium
C) fuse helium into carbon
D) fuse all elements into iron
6. What type of spectrum will a cold solid object produce?
• A) continuum
• B) emission
• C) absorption
• D) this object will not emit light of any type
7. What will our sun become when it dies?
• A) nothing (it will blow itself apart in a fiery supernova that destroys everything)
• B) a black hole
• C) a neutron star
• D) a white dwarf
10) The first Exosolar planets discovered (Exosolar means planets orbiting other stars)
were found by:
A) taking images of the planets
B) by radio signals emitted by the planets
C) by watching the star the planet orbits wobble
D) we have not yet found any planets outside our solar system as those objects are
still very theoretical
12) If we know a star’s apparent and apparent brightness then what do we also need to
figure out in order to determine the distance to that star?
• A) age of the star
• B) temperature of the star
• C) absolute brightness of the star
• D) we will need all of these
13) At the end of our sun’s life our sun’s death will generate a:
A) supernova
B) nova
C) planetary nebula
D) black hole
18) What group is currently looking for intelligent life in the universe?
A) NASA
B) NSF
C) SETI
D) NSA
22) In the 1950’s the spectra from quasars revealed emission lines that matched no
known elements. Why was this?
• A) quasars are made of elements which were not known in the 1950’s
• B) there were mistakes made with the observations
• C) there were Doppler shifts of more than 50%
• D) the astronomers forgot to take relativity into account
26) Which molecule, if found in abundance, would be smoking gun evidence of life in
that planet in some form?
• A) Carbon Dioxide
• B) Argon
• C) Water
• D) Ozone
28) About how long does it take light to pass through the Radiative Zone of our sun?
A) less than a minute
B) between a few hours and a few days
C) between a year and a hundred years
D) more than 100,000 years
29) Why does it take the time it takes for light to pass through the Radiative Zone of our
sun?
A) light travels very quickly
B) time slows down due to relativity
C) the Radiative Zone of our sun is solid
D) the light is constantly absorbed and reemitted in a random direction
30) How do we find the recessional velocities of galaxies (so that we can use Hubble’s
Law)?
• A) parallax
• B) measuring the rate of change of the size of the galaxy
• C) comparing the observed wavelength of Hydrogen emission lines to the actual
wavelength
• D) all of the above
31) Quasars are typically found?
• A) on the other side of the observable universe (< 4 billion light years)
• B) in the cores of the nearest galaxies to us (less than 100 million light years)
• C) in the cores of nearby galaxy clusters (200 million to 2 billion light years)
• D) Quasars are found equally at all distances from us
32) What are quasars?
• A) newly formed galaxies
• B) supermassive black holes
• C) massive supernovae
• D) reflections of the big bang
35) A planet with no atmosphere and no magnetic field:
A) cannot have life on it anywhere
B) could have life but only on the surface
C) could have life but only if it had a global ocean on the surface
D) could have life under the surface
37) The atmosphere of the earth is “thin” to most light and is colder than the surface.
What type of spectrum would you expect to get from the earth?
• A) continuum
• B) emission
• C) absorption
• D) no light will get through the Earth’s atmosphere
38) Which of the following is NOT something astronomers have used to measure
distances to objects?
A) Parallax
B) Variable Stars such as RR Lyrae and Cepheids
C) Hubble’s Law
D) Astronomers have used all of these to measure distances
39) Stars are formed when:
A) giant molecular clouds collapse
B) a supernova scatters material into the Interstellar Medium
C) a bubble bursts through the galactic plane
D) a white dwarf collapses upon itself
40) HR diagrams have to compare stars which have brightnesses which differ by factors
of tens of thousands. Therefore, to handle this, what type of chart is the HR diagram?
A) linear plot
B) sky plot
C) 3-D plot
D) log-log plot
41) What determines the absolute brightness (and therefore temperature) of a main
sequence star?
• A) its age
• B) its distance from us
• C) its mass
• D) its spin rate
42) You observe two variable stars. Star A has a mass of 2.5 solar masses. Star B has a
mass of 3.2 solar masses. Which one will have a longer pulsation period?
A) Star A
B) Star B
C) They will have about the same pulsation period
D) You cannot tell from the data provided
44) If an object has a parallax of 0.01 arcseconds then how far from the earth is it?
• A) 1 parsec
• B) 0.01 parsec
• C) 100 parsec
• D) 0.01 lightyear
46) Two stars form within a few light years of each other. The first is a 10 solar mass
star and the 2nd is a 2 solar mass star. Which will live longer?
A) the 2 solar mass star
B) the 10 solar mass star
C) they live the same amount of time
D) mass does not determine the lifetime of the star
47) When a 10 solar mass star dies what is left over?
A) a white dwarf
B) a neutron star
C) a black hole
D) nothing
48) Which of the following stars will undergo a supernova at the end of its lifetime?
A) a star the mass of the sun
B) a star at least 10 times the mass of the sun
C) a star less than half the mass of the sun
D) all of these stars will undergo a supernova at the end of their lifetimes
51) What is the Lyman-alpha forest?
A) the method to determine the mass of a quasar
B) the area that the telescope that discovered the first quasar was housed
C) the type of galaxy that quasars are commonly found in
D) the spectra we receive from quasars
52) What can we learn from the Lyman-alpha forest?
A) the masses of quasars
B) about the galaxies and clouds of gas in the path between us and the Lymanalpha forest
C) about what the quasars are made out of
D) all of the above
55) What is the best method to find the distance to Alpha Centauri (4.3 light years away)?
A) parallax
B) variable stars
C) Hubble’s Law
D) star cluster fitting
56) What is the best method to find the distance to Andromeda Galaxy (3 million light
years away)?
A) parallax
B) variable stars
C) Hubble’s Law
D) star cluster fitting
57) What is the best method to find the distance to M15 (a globular cluster) (15000 light
years away)?
A) parallax
B) variable stars
C) Hubble’s Law
D) star cluster fitting
58) What is the best method to find the distance to a spiral galaxy that is 100 million light
years away?
A) parallax
B) variable stars
C) Hubble’s Law
D) star cluster fitting
Cluster A
M15
12
14
16
V
18
M15
20
22
-0.50
24
0.00
0.50
1.00
1.50
B-V
2.00
Cluster B
Questions 59-62 refer to the 2 clusters above
59) If the sun were to be located in Cluster B then what would the sun’s B-V value be (as
viewed from the earth B-V = 0.68)?
A) 0.68
B) 6.8
C) 0.068
D) it is impossible to know without determining the exact distance to the cluster
60) If the sun were to be located in Cluster A then what would the approximate V value
of the sun be (the sun as view from Earth has a B-V = 0.68)?
A) 3
B) 8
C) 12
D) 15
61) Which cluster is older?
A) cluster A
B) cluster B
C) both clusters are the same age
D) it is impossible to compare the ages of these two clusters
62) Which cluster is further from the earth?
A) cluster A
B) cluster B
C) both clusters are the same distance from the earth
D) it is impossible to compare the distances of these two clusters
64) Of all the Carbon, Nitrogen, and Oxygen in our bodies, about what percentage of
those atoms were formed in the first 10 minutes of the universe?
A) 0%
B) 10%
C) 50%
D) 100%
70) The limitation on using parallax to measure distance is set by:
A) the curvature of the universe
B) the brightness of the stars
C) the ability to measure positions accurately
D) all of the above
71) Cepheid variables allow you to calculate distances because:
A) their absolute brightness is determined from their color
B) their apparent brightness is determined from their color
C) their absolute brightness is determined from their period
D) their apparent brightness is determined from their period
83) Which of the following is NOT a necessity for life as we know it (life in general, not
human life)?
A) pressure
B) an atmosphere
C) liquid water
D) these are all necessities for life as we know it
84) Which of the following is NOT a necessity for life as we know it (life in general, not
human life)?
A) ozone
B) an energy source
C) a temperature range where you can have liquid water
D) these are all necessities for life as we know it
85) The method to estimate the number of expected intelligent civilizations in our galaxy
is called:
A) Hubble’s Law
B) The Drake Equation
C) The Tully-Fisher Relationship
D) Parallax
86) In order to be able to determine if there might be life on an Earth sized planet what do
we have to be able to do?
A) Use a space based interferometer
B) Block out the light from the star the planet is orbiting
C) Take a spectrum of the planet
D) Even though one of these is needed a bit more than the others all of A-C are
necessary
Section 2: Short Answer. 50 pts per question.
1) Tastronaut = Tuniverse / Gamma
Lmotion = Lrest / gamma
Tastronaut = Tuniverse / (1 – Rs/R)1/2
Gamma = 1/(1-v2/c2)1/2
distance = velocity * time
c = 1 lightyear /year
Rs = 1.5 km * Mass of star (in solar masses)
NOTE: ½ power means square root (so do not multiply those by 0.5 please…)
An astronaut comes up with an idea to become insanely rich. They will put $100k into a
index fund which makes about 8% profit per year. From an economic rule of 72 this
means that he would double his money every 9 years. So, the amount of money he will
have after N years will be $100k * 2(N/9). From his own perspective the astronaut will be
gone for a total of 6 years (3 years out and 3 years back). If the astronaut traveled at a
velocity of 99.967% then find:
A) The total time that the trip will consume from the perspective of the Earth.
B) If the astronaut traveled out to a star and then back how far from the earth in light
years was the distance to the star?
C) If the length of the spacecraft at rest is 100 m what is the length the spacecraft will be
from the perspective of the Earth?
D) When the astronaut returns home how much money would they have?
Vr km/s
2) You will find the following equations useful for this question:
Mass function = Period (in years) * (radial velocity / 30 km/s)3
(mass of the 2nd star)3 = Mass function * (Mass of first star) 2 / (sin(inclination))3
100
80
60
40
20
0
-20 28
-40
-60
-80
-100
Cyg X-1
33
38
43
Julian Day +2450200
Vr is in units of km/s and JD is in units of days. Find:
A) Find the orbital period for the system
B) Find the radial orbital velocity of the star
C) Find the mass function of the system. Also in a sentence explain what the mass
function represents and why it does not necessarily give the true picture.
D) If the first star has a mass of 30 solar masses and the inclination is 40 degrees then
what is the mass of the secondary star?
3) A) Name the 8 most basic building blocks of life.
B) Explain the top 2 methods of finding Exo-Solar planets.
C) Can these two methods find life, why or why not, and if no explain what we need to
do to be able to find life?
D) How much time will we need to wait until we are able to find earth massed planets in
a habitable zone (and not the 13 earth mass just recently found does not count) and how
long until we will be able to find life on other planets?