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Astronomy 100
Sample final exam (comprehensive)
Open book, exercises, projects and notes, no collaboration. You have two hours
for this 100-point test.
Short answer: Answer all questions
1. Match the term (left column) with its correct usage (right column)
Neutron star
Crab Nebula today
White dwarf
Crab Nebula in 1054
Supernova
Ultimate fate of a G-class star
Supernova remnant
Ultimate fate of an A-class star
Questions 2 through 4 refer to the orbital diagram below:
2. Draw the ion tail and the dust tail of the comet where it is positioned. Label
the tails clearly.
3. The eccentricity of this comet’s orbit is:
a. zero
b. between zero and one
c. one
d. greater than one
4. This comet has a semi-major axis similar to that of Jupiter. Give a simple
two or three word explanation why it will never hit Jupiter.
5. Which of the following is produced by the proton-proton cycle in the Sun?
Choose all that are correct.
protons
neutrons
neutrinos
helium nuclei
carbon nuclei
6. What is the color of the brightest stars in a very old star cluster? Choose one.
Blue-white
Yellow
Orange
Red
7. Order the following events from oldest (1) to most recent (4):
chondrules
solar nebula
planetesimals
creation of Moon
8. The Sun is currently luminosity class _______ , but when it reaches the
end of its hydrogen fusion phase, it will become luminosity class
_______ .
9. The graph above is:
a. A Hertzsprung-Russell (H-R) diagram
b. An illustration of the Doppler shift
c. The Hubble Law
10. Meteorites made of nearly pure iron and nickel originally came from:
a. a comet
b. an asteroid that underwent differentiation
c. an asteroid that did not differentiate
d. the core of the Earth
11. In the space within 20 ly of the Sun, the predominant class of star is (choose
one):
O
B
A
F
G
K
M
d
12. Match the equation with its appropriate use:
F = G
I =
€
m1 m2
r2
k
d2
€
λ
− λrest
vradial
= shift
c
λrest
€
d =
€
1
p
The distance to an open cluster
The speed of a probe at any point
in its orbit
The force between binary stars
The distance to a nearby star
M = fobjective/feyepiece
The redshift of a galaxy
2 1
v 2 = G(m1 + m2 ) − 
r a
How much a telescope magnifies
13. The aurora borealis shows that (choose all that apply):
a. The Sun has a magnetic field
b. The Earth has a magnetic field
c. There are charged particles coming towards us from the Sun
d. The Earth is generating charged particles and they are being shot up into space
Philosophy section
14. A philosopher once said “Given the billions of stars in the Milky Way, surely
one other one must have a planet that has complex life forms.” Can this
statement be tested scientifically? In a few sentences, either describe an
experiment that could test this statement, or explain why this statement cannot
be tested scientifically. Assume that we have no magic or super-advanced
technology.
Calculation section Choose two of the following problems; select the
appropriate equation, complete the calculation (show all steps) and answer any
follow-up questions for full credit. Hint: the equations necessary for this section
are either on this exam, on a previous exam, an exercise or in your notes.
15. Neutron stars have a surface temperature of 1,000,000 K (1 × 106 K). What is
the wavelength of maximum intensity of these stars? What part of the
electromagnetic spectrum is that wavelength located in?
16. The Meade telescope in North Seattle CC’s dome has a primary mirror
diameter of 0.25 m and a focal length of 2500 mm. Given that it is most sensitive
to yellow light whose wavelength is 5 × 10-7 m, calculate the resolution of this
telescope (in arc-seconds). Will Neptune at its largest (2.4 arc-seconds) appear
as a point or a disk through this telescope? Explain briefly.
17. An object orbits the Sun with a period of 350 years. What is its semi-major
axis? How would you classify (composition or type) this object? In other words,
what is it?
Essay section part one Choose two of the following discoveries, and
determine if they are surprising (not consistent with current astronomical ideas)
or not surprising (consistent). In either case, state clearly the astronomical idea
or ideas that apply to the discovery.
18. An extrasolar planet is discovered orbiting its Sun-like star at a distance of
about 1 AU. The planetary atmosphere is about the same density as Earth’s but is
made nearly entirely of carbon dioxide. The planet’s surface temperature is 300 K
(27°C).
19. Neptune is found to have a set of rings made of trillions of roughly basketballsized ice particles orbiting above its equator.
20. A solar system of twelve planets is discovered orbiting another star. Though
all of the planets orbit on roughly the same plane, all the terrestrial worlds orbit
counterclockwise and all the Jovian worlds orbit clockwise (as viewed from the
system’s north pole).
21. An active volcano is discovered on Venus.
Essay section part two Choose two of the following and answer it in a
paragraph or so.
22. Carl Sagan famously said that we are all made out of “star stuff”. Let’s follow
that line of thought – assume you are made out of nothing but carbon, hydrogen
and oxygen. Where was the ultimate origin of all of the atoms of these
elements that are now in your body? Caution: they may have separate origins!
23. Classify the galaxy above, and state what color you would expect this galaxy
to be. To help with your classification, this galaxy emits more radiation, from
gamma rays to radio waves, than the Milky Way does. Explain why this type of
galaxy would be expected to emit such extra radiation.
24. The graph above shows the spectrum of a planetary atmosphere, using a
device very similar to the spectrometer you used at the end of Exercise 5. The yaxis is intensity of the light (in arbitrary units) and the x-axis is wavelength,
measured in µm (micrometers or microns). You want to set up a ground-based
telescope to observe the night sky in these wavelengths; one colleague (George)
suggests observing in the range of 11 to 12 microns, while another colleague
(Martha) suggests observing in the 14-15 micron range. One of them is correct;
which suggestion do you go with, and why?
25. Below are some characteristics of stars. Your task is to separate them into
two categories: the characteristics we can directly observe, and the characteristics
we must infer (in other words, figure out by models or equations). Write a
sentence for each to explain either what instrument is used to measure it or how
we use another number to infer this characteristic.
• apparent brightness
• spectral type
• radius
• mass