Download 12/08/14-- Student ID ______ TA Name

Full Name _____________________________________________ Date --12/08/14-- Student ID ____________
TA Name ___________________________________________Section ______ [8 PAGES - 44 QUESTIONS]
1. Here is a series of moon phases, top row, starting with the new moon on November 22, a full moon on
December 6, and a new moon on December 22. What does today’s moon phase look like? Choose among those
phases labeled “A, B, C, D, or E” – all are labeled December 8, but only 1 is correct.
Figure 1. Phases of the Moon from November 22 to December 22, 2014
The phases of the moon progress smoothly. “C” is the correct answer, and if you examine the full moon just
above, you will see that “C” is not a perfect circle. Besides, it is just 2 days past the full moon. “B” cannot be
right because there are 6 days between the 8th and the 14th when there is a 3rd quarter moon – and the moon takes
about 7 days between full and 3rd quarter.
2. No matter where you live on Earth, there is a location that has the same latitude but is 180° away in
longitude (on the opposite side of Earth). The next new moon for us is December 22. When is the next new
moon for people living on the opposite side of the Earth?
a. December 8 (today)
b. December 15
c. December 22
d. December 29
3. First, remove Earth’s atmosphere; then, climb to the roof of the UW Tower and drop a
hammer and a feather. What is the physical explanation for the objects falling at exactly the
same acceleration?
a. The larger force needed to accelerate the hammer comes from the equally larger mass,
so the acceleration of the hammer and feather remains the same.
b. Everyone knows that objects fall at the same rate on Earth, 9.81 m/s2.
c. The mass of the Earth is so much greater than the mass of even the hammer that the
gravitational force on each object is identical.
d. Because the feather has more inertia than the hammer, it is able to fall to the Earth
faster and thus will hit the ground at the same time as the hammer.
Figure 2. A recreation of the astronauts on the Moon experiment
4. Superman left the planet Krypton as an infant 27 years ago just before its destruction. Krypton orbited the
star Caph, a spectral type F star. Caph is 54 light years away; thus Superman could have looked back in time
and seen his home blow up. Here’s the question: The full spectrum of light was emitted during the explosion
of Krypton. Which kind of signal reached Superman first and why?
a. X-ray signals because x-rays have the high energy, high frequency, and thus faster speed.
b. Radio signals because although they have the lower energy, the wavelengths are very long.
c. Visible light captured by the Hubble Space Telescope because of its being above the atmosphere.
d. All are forms of electromagnetic radiation traveling at light speed and thus reached us at the same time.
9 December 2014
final-exam_autumn2014-analysis.docx
1
5. Which one of the following statements is NOT correct about the relationship among the luminosity, surface
temperature, and overall color pattern of a star?
a. The luminosity, surface temperature, and overall color pattern of a star are related.
b. The cooler a star is, the less luminous it is, and its spectrum will peak at longer wavelengths.
c. The hotter the star, the more luminous it is, and the brighter the colors will be overall.
d. For stars having orbiting planets, if the surface temperature of a star increases, its luminosity does not.
DIRECT from one of the quizzes
Figure 3. Thermal radiation curves of four stars.
6. What information about these 4 stars could be inferred directly from values on this chart?
a. The approximate distances they are from Earth in parsecs.
b. Whether or not they will go supernovae or form planetary nebulae.
c. Fairly reliable estimates of their surface temperatures.
d. Their parallax shifts when their luminosities are known.
7. What is the difference between the interstellar medium (ISM), a molecular cloud, and a protostar?
a. The ISM contains everything: hot gas, dust, molecular clouds, stuff not part of a protostar.
b. The only difference is density: protostars are less dense than the ISM and molecular clouds.
c. The ISM is a broad category that excludes molecular clouds, protostars, and also HII regions.
d. The ISM is much cooler and denser than either a molecular cloud, an HII region, or a protostar.
8. You have examined images of cool dust shown glowing in “false” colors. The colors represented have to
be called “false” because the overall blackbody (thermal) curves peak at wavelengths
a. in the ultraviolet part of the spectrum.
b. in the visible part of the spectrum but at colors unknown to us.
c. in the infrared part of the spectrum.
d. that are much longer than microwave wavelengths.
2
Figure 4. Cut away of the Sun (left) and approximate temperatures above the photosphere and to the core. The heights in
the right-hand figure are not exact. A points to dark features on the photosphere, which is represented by B.
Use Fig. 4 to answer the next 5 questions.
9. (1 pt) Contains the coolest region where absorption lines form. B
10. (1 pt) Energy gets through this region via the “random walk.” D
11. (1 pt) Magnetic fields from Sun’s interior poke out in these photospheric dark regions. A
12. (1 pt) The “boiling” movement of the gas transports energy through this region. E
13. (1 pt) The only region where fusion occurs. C
14. Both of the following statements are either True (a) or False (b): If a star has an apparent magnitude of 5 it
is brighter than a star whose apparent magnitude is 8. If a star has an absolute magnitude of −6, it is more
luminous than a star whose absolute magnitude is −1.
Covered in lecture, covered when working on the CMDs, covered indirectly with the distances to the clusters,
included on an HR Diagram….
15. Particles and energy are produced in the proton-proton fusion cycle of the Sun and other stars. What part of
the fusion cycle is most responsible for supporting the Sun against gravitational collapse?
a. the neutrinos that are formed in the first step.
b. the positrons that are formed in the first step.
c. the gamma rays that are produced in steps 1 and 2.
d. the two protons released at the end when the helium nucleus is created.
What does the fusion process produce? Neutrinos go straight out unimpeded; positrons annihilate with electrons
to produce gamma rays; two protons at the end only get put back into the next fusion process. We worked
through the whole proton-proton cycle sheet in lecture, and the image was included in the cover sheet with the
exam. TO BE REGRADED.
Star Name
Asellus Borealis
Asellus Australis
Acubens
Al Tarf
kappa Cancri
Spectral
Type
A1 IV
K0 III
A5 V
K4 III
B8 III
Apparent V
Magnitude
4.67
3.94
4.26
3.52
5.24
Parallax
(arc sec)
0.018
0.025
0.017
0.011
0.006
Figure 5. The constellation Cancer and named and numbered stars (Star
information gathered from SIMBAD.)
The constellation Cancer will cross the meridian at midnight on February 2, 2015. Review the data listed in the
above table on 5 of its brightest stars and answer the following 4 questions.
16. (1 pt) Which of these two stars – a. kappa Cancri (0.006) or b. Asellus Australis (0.025) – is farther away?
3
17. (1 pt) Which of these two stars – a. Acubens (A5V) or b. Al Tarf (K4III)– has a higher temperature?
OBAFGKM
18. (1 pt) Which of these two stars – a. Al Tarf (3.52) or b. kappa Cancri (5.24) – is brighter?
Smaller apparent magnitude means brighter. Emphasized many times in lecture; worked on in fitting the main
sequences of the clusters.
19. Asellus Australis and Al Tarf are both K giants, with close to the same brightness, and yet Al Tarf is over
two times farther away. Which star must be more luminous?
a. Asellus Australis
b. Al Tarf
c. Not enough information is given to answer this question.
Same brightness in the sky, but one is 2 times farther away. The one that is farther away has to be more
luminous if it is farther away but has the same brightness in the sky.
There are two open clusters “in” Cancer, Messier 44 (Praesepe) and Messier 67, indicated by the circles, arrows,
and labels in Fig. 5. Here are their actual color-magnitude diagrams.
20. Which cluster is older?
a. Messier 44 (M44)
b. Messier 67 (M67)
21. If a main sequence star in M44 with B - V
= 1 has an apparent magnitude of 13.5 and a
main sequence star in M67 with B - V = 1 has
an apparent magnitude of 16.5, which cluster is
farther away?
a. Messier 44 (M44)
b. Messier 67 (M67)
c. Not enough information is given.
a. Praesepe
b. Messier 67
Cluster fitting activity; also, along the main
sequence, stars have same mass that have same
temperature and have same luminosity ! a
primary feature of the HR Diagram. Thus, at a
given temperature, the dimmer the star, the
farther away the cluster is.
Figure 6. The color-magnitude diagrams of 2 open clusters in the constellation of Cancer. The solid, curvy line indicates
the location of the theoretical main sequence for each cluster.
Figure 7. Three RR Lyrae variable stars varying in visual magnitude over time. RR Lyrae variable
stars all have nearly identical average absolute magnitudes, meaning nearly identical luminosities.
The x-axis is showing a compressed version of time; the y-axis lists the visual magnitudes and ranges
of variation.
22. The star A has a mean apparent magnitude of ~14; star B, ~12.5; and star C, ~8.0.
Which answer correctly lists the stars from the closest to the farthest?
a. A, B, C
b. B, C, A
c. C, A, B
d. C, B, A
The larger the apparent magnitude number, the dimmer the stars. Since these stars all have
the SAME absolute magnitude – the same luminosity – the ones that have the larger apparent magnitudes have
to be farther away. TO BE REGRADED. Scantron key was erroneously marked.
4
23. Why do the more massive stars, those having more than 10 times that of the Sun, go through stages that are
quite different from Sun-like stars?
a. Larger force of gravity causes the interior temperatures to be higher throughout their lives.
b. Fusion rates are much higher, a necessity to provide the higher luminosity needed for support.
c. Moving from one type of fusion to the next higher one does not involve any core “flashes.”
d. Neutron degeneracy must act to support the more massive cores of high-mass stars.
e. All of the above answers contribute to the different end results of these massive stars.
C Barred spiral
A Elliptical
B Irregular
D Spiral
Figure 8. Use the above images of galaxies and their labels to answer the following 2 questions.
24. This galaxy looks yellow-orange because there has been no star formation for a very long time.
25. These types of galaxy are likely to have on-going formation of massive stars
a. elliptical, barred spiral, and irregular
b. irregular and barred spiral only
c. irregular, barred spiral and spiral
d. all of the Hubble types of galaxies
5
Figure 9. The image of the Rosette Nebula, left, shows
a star-forming region about 5200 light years away
located in the constellation of Monoceros. The picture
was taken at visible wavelengths. The center cavity of
the nebula shows a young cluster of hot, massive O & B
stars. A spectrum that shows a strong emission line of
hydrogen is given below the image of the nebula. There
are also regions of dark dust.
Notice that the line is identified as H-alpha in the
spectrum
26. The spectrum in Fig. 9 shows an extremely strong red emission line of hydrogen at
656.3 nm. This emission line is most likely the result of light coming from the
a. cool (~10 K), glowing dark pillars of dust surrounding the star cluster.
b. reddening due to the left over dust from star formation.
c. large number of red giant and supergiant stars in the cluster.
d. excited, diffuse hydrogen gas surrounding the star cluster
27. Which of the following electron transitions represents the one producing the emission
line at 656.3 nm?
a. A - transition from level 2 to 1
b. B - transition from level 3 to 2
c. C - transition from level 4 to 2
d. D - transition from level 5 to 2
e. E - transition from level 6 to 2
Figure 10. Electron transitions of the hydrogen atom.
28. Observations have shown that the stars found in globular clusters have less than 0.01% abundance of
elements heavier than helium. Most stars located in the disk of the Milky Way have much higher abundances of
"heavy elements" such as carbon, nitrogen, oxygen, iron, magnesium, etc. This fact implies that the halo stars
formed
a. billions of years after the disk stars but from clouds containing only hydrogen.
b. before the disk stars when the interstellar medium had not yet been enriched.
c. before the stars located in the disk and were captured from other spiral galaxies.
d. immediately after the Big Bang, even before the cosmic background radiation was formed.
29. The hunt for and detection of cosmic rays is currently a very active research field in astrophysics. One of
the reasons is that the mechanism that produces these high energy particles
a. leads astronomers to the location and frequencies of supernovae.
b. shows the structure of the Universe just after the Big Bang.
c. traces the rotation direction of the spiral arms of galaxies.
d. comes from collapsing giant molecular clouds in elliptical galaxies.
Reading Quiz 9:
What mechanism gives the cosmic rays such extremely high energies?
!Shock waves produced by supernovae explosions.
The collapse of the giant molecular clouds due to gravity.
The high spinning velocity of the Galaxy close to its supermassive black hole.
All of these mechanisms individually or together give the cosmic rays high energies.
6
30. What knowledge do we use to support our confidence in using Type Ia supernovae as reliable distance
indicators?
a. the evolution of stars and the interaction of a red giant and white dwarf binary system
b. the universal cosmological principle where there is no special place in the Universe
c. the theory of general relativity that states the oneness of space and time
d. the use of look-back time and telescopes as time machines to view the distant past
Because all of this type of supernovae come from white dwarfs that have roughly the same mass and
the same process produces the supernovae.
31. What observations provide evidence that our theories about Type Ia supernovae are correct?
a. observations of supernovae occurring in galaxies having independently derived distances
b. Hubble’s observation of the expanding universe back in the early 1900’s
c. supermassive black holes at centers of galaxies and the rapid motion of stars close to them
d. observations of distant galaxies and then comparisons with nearby galaxies
32. It is ironic that the observations of RR Lyrae stars in globular clusters (1920’s), with the goal of disproving
that the Milky Way was just one of many galaxies, showed us something quite different. Almost over night we
discovered that
a. a huge volume of dark matter and dark energy surrounds the Milky Way.
b. our solar system was just one of many planetary systems in the Orion Arm of the Galaxy.
c. our solar system was not located close to the center of the Milky Way.
d. globular clusters must have formed simultaneously with the formation of the Milky Way.
33. By taking the inverse of Hubble’s constant and adjusting the
units, we can calculate the amount of time that the Universe has been
expanding since the Big Bang – its age. Figure 11 shows the
dramatic decrease in the value of Hubble’s constant from about 600
km/sec per Mpc in 1925 to approximately 70 km/sec per Mpc today.
This dramatic decrease implies that
a. the Universe is much older than original estimates.
b. the Universe is much younger than original estimates.
c. there is a conflict with the ages of the oldest stars.
d. the original value that Hubble calculated is correct.
Figure 11. The changes in the Hubble constant over the past century.
7
Figure 12. Spectra of the two spiral galaxies in the region of the hydrogen-alpha line at 656.3 nm (6563 Å). The vertical
lines highlight the peaks of some of the identified elements: hydrogen and singly ionized nitrogen and sulfur atoms. The
respective cosmological redshifts are 0.0017 and 0.0041. Note the similarity overall in these spectra that allows accurate
identification of the emission lines.
34. Figure 12 shows a small spectral region of two galaxies. The cosmological redshift of the spectrum of NGC
2903 is 0.0017; and that of NGC 6217, 0.0041. The ratio of the redshifts is 2.4. This implies that
a. NGC 2903 is more than twice as far away as NGC 6217.
b. NGC 6217 is more than twice as far away as NGC 2903
c. NGC 6217 is more than two times older than NGC 2903.
d. both of these galaxies are in the same region of the Universe.
35. Many of you found a discrepancy in the activity involving the expansion rate and age of the Universe
between the distances implied by the listed redshifts and the published distances listed in the last column.
Hubble’s law states that: 𝑣 = 𝐻! 𝑑 𝑜𝑟 𝑑 = 𝑣 𝐻 . There is a similar discrepancy in the published distances of
!
the two galaxies of Fig. 12. What would be the most logical reason?
a. The galaxies are actually at the same distance, but the spectra are misleading.
b. The galaxy that is assumed to be more distant is actually just physically smaller.
c. The published distances to these galaxies assumed different values for Ho.
d. Hubble’s constant is not a constant and different values would apply to individual galaxies.
I covered this specifically in the review session – emphasized it. Plus, all through the last part of the
quarter we talked about the different values of Ho and how they changed throughout the past decades.
36. There are ways to independently determine the distances to these two galaxies, which are both more than 30
million light years away. The obvious method to use would be
a. the parallax of a number of stars in each galaxy.
b. RR Lyrae stars in the globular clusters of each galaxy.
c. observing Cepheid variables and Type Ia supernovae in each galaxy.
d. Hubble’s law.
These galaxies are 30 million light years away! Parallax takes us just around 600 light years away in the Milky
Way. Last question on the parallax lab. Even if one didn’t recall that, we’ve been emphasizing Type Ia
supernovae a lot.
37. Using the concept of look-back time, which one of the following answers is correct?
a. The galaxies with the highest redshifts will look the oldest.
b. The most distant galaxies will look the youngest.
c. The closest galaxies to us will be the youngest.
d. The galaxies with the highest redshifts will be the oldest.
8
38. The astrophysicists in “The Runaway Universe” video had been granted observation time on some of the
best telescopes in the world. What was the original goal of their research and what kind of surprise did they
find?
a. to view the cosmic microwave background radiation; it was primarily gamma ray radiation
b. to figure out the current value of the Hubble constant; galaxies far away were not expanding
c. to find out if the expansion of the Universe is slowing; the expansion is accelerating
d. to count all of the Type Ia supernovae in each galaxy; only nearby galaxies had supernovae
39. Light has a finite speed. We are able to gain insight as to how galaxies evolve over time by studying the
galaxies at various redshifts in the Hubble Deep Fields because
a. the farther away a galaxy is the longer its light has taken to reach us and the older it seems.
b. galaxies at larger and larger redshifts will look progressively younger and younger.
c. since the Big Bang, galaxies have been gradually evolving from spiral to elliptical types.
d. although galaxies were all born at roughly the same time, the closest ones are the youngest.
40. Suppose astronomers had found that at high redshifts, the percentage of elliptical galaxies in the Hubble
Deep Field North was much lower than the percentage of elliptical galaxies in the nearby universe, while the
opposite was true for the percentage of spirals. Which one of the following logical conclusions has the most
observational support?
a. Some spiral galaxies have merged with other galaxies and eventually formed elliptical galaxies.
b. As spiral galaxies age, they go through stages: irregular, spiral, barred spiral, elliptical.
c. Elliptical galaxies were formed right after the Big Bang, but then evolved into spirals.
d. There are equal numbers of ellipticals and spirals at high redshifts, we just can’t see them.
41. The spectrum of the cosmic microwave background radiation is the closest thing we have observed to a
perfect blackbody spectrum. This spectrum tells us that the early universe was
a. opaque
b. dense
c. of nearly uniform temperature
d. All of these conditions were present.
42. There are two basic models of how the structure of the Universe formed: 1) Large structures formed first and
then fractured into smaller and smaller segments that later became galaxies and stars. 2) Smaller structures
formed first and gradually merged or otherwise grouped to form large structures. The second scenario is
currently favored and is given the name
a. hierarchical clustering
b. anisotropic clustering
c. archetypal clustering
d. oligarchical clustering
Reading Quiz 10: What is meant by "hierarchical clustering" in the early universe? (Choose the BEST answer,
which is probably the simplest one.)
a. Smaller structures in the universe formed first and then became the pieces that came together to form
larger structures.
b. Slight ripples in the cosmic microwave background formed structures the size of atoms that later
combined to form simple - then complex - molecules.
c.
must be exactly equal to 1 so that the expansion of the universe is slow enough for
structures to form.
d. The balance among radiation, normal matter, dark matter, and dark energy was such that smaller
structures were able to merge.
9
43. Astronomers (led by Alan Guth in the 1980's) hypothesized a very early period of rapid expansion of the
Universe known as inflation in order to explain why the universe was much too flat and the cosmic microwave
background much to smooth: Ωmass + ΩΛ=1 (or incredibly close to it). Each of the following represents
predictions of the period of inflation, except one. Which one should not be included?
a. Space expanded rapidly; distances between points in space increased faster than light speed.
b. This period would have created parallel universes that were too far apart to be detectable.
c. Any curvature of the universe would not be apparent from any location.
d. Fluctuations caused by quantum uncertainty are much too large today to be measureable.
Reading Quiz 10
Astronomers (led by Alan Guth in the 1980's) hypothesized a very early period of rapid expansion of the
Universe known as inflation in order to explain why the universe was much too flat and the cosmic microwave
background much to smooth:
Ωmass+ΩΛ=1(or incredibly close to it). Each of the
following represent predictions of the period of inflation, except one. Which one should not be included?
a. Around the age of
seconds, the scale factor of the universe increased by a factor of
or more.
b. Space expanded so rapidly that distances between points in space increased faster than the speed of light.
c. Any curvature of the universe would not be apparent from any location.
d. The large fluctuations caused by quantum uncertainty are much too large today to be measureable.
Correct Answer :
e. The sudden inflationary period would have created parallel universes that were too far apart to be
detectable.
44. The cosmological principle is a testable scientific theory. Which one of the following is a prediction of the
cosmological principle?
a. Students studying in a classroom 2 billion light years away would reach different conclusions about the
Universe than we do.
b. The distribution of galaxies viewed from a planet orbiting a star 10 billion light years away is the same
as the distribution of galaxies viewed from Earth.
c. If we observed more spiral galaxies at 5 billion light years away in one direction, we would find that
there were more elliptical galaxies at the same distance away in the opposite direction.
d. If space explorers were able to immediately travel 13.7 billion light years away, they would be able to
see the Big Bang in process.
“The Cosmos extends, for all practical purposes, forever.
After a brief sedentary hiatus, we are resuming our ancient
nomadic way of life. Our remote descendants, safely
arrayed on many worlds throughout the Solar System and
beyond, will be unified by their common heritage, by their
regard for their home planet, and by the knowledge that,
whatever other life may be, the only humans in all the
Universe come from Earth. They will gaze up and strain to
find the blue dot in their skies. They will love it no less for its obscurity and fragility.
They will marvel at how vulnerable the repository of all our potential once was, how
perilous our infancy, how humble our beginnings, how many rivers we had to cross
before we found our way.”
― Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space
10
Please make sure that you have bubbled in your name, student ID number, and section.
……….Have a wonderful, fun, enlightening winter break!..........
11