Introduction to Astronomy
Exam Answer Key
Course Introduction
Introduction to Astronomy offers an exploration of the universe beyond our planet, guiding students through fundamental concepts such as the structure and evolution of stars, galaxies, and planetary systems. The course covers observational techniques, the physical principles underlying celestial phenomena, and humanitys place in the cosmos. Emphasizing both historical context and cutting-edge discoveries, it encourages scientific inquiry and critical thinking while providing a broad understanding of the night sky, the solar system, and the broader universe.
Recommended Textbook
Astronomy The Universe at a Glance 1st Edition by Eric Chaisson
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Page 2
Chapter 1: The Night Sky
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Sample Questions
Q1) Where would you be if the Sun passes directly overhead on December 21st?
A) Equator
B) Tropic of Cancer
C) Tropic of Capricorn
D) Antarctic Circle
E) South Pole
Answer: C
Q2) The celestial sphere appears to move fastest above the ________.
Answer: equator
Q3) You note that a particular star is directly overhead. It will be directly overhead again in
A) 1 hour.
B) 12 hours.
C) 23 hours 56 minutes.
D) 24 hours.
E) 24 hours 4 minutes.
Answer: C
Q4) The ________ of the Earth causes the Sun and Moon to rise in the east and set in the west.
Answer: rotation
Page 3
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Chapter 2: Light and Telescopes
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Sample Questions
Q1) An emission spectrum can be used to identify a(n)
A) proton.
B) electron.
C) neutron.
D) atom.
E) neutrino.
Answer: D
Q2) In astronomy, an interferometer can be used to
A) yield better seeing conditions with optical telescopes.
B) decrease the effects of light pollution in getting darker sky backgrounds.
C) improve the angular resolution of radio telescopes.
D) increase the sensitivity of infrared telescopes to longer wavelengths.
E) speed up the processing of CCD images.
Answer: C
Q3) Explain how Bohr's model creates emission and absorption lines in the spectrum.
Answer: Bohr's model has the electron orbitals quantized into discrete energies. Each upward transition to a higher energy state produces an absorption line (energy is absorbed). Each downward transition produces an emission line (energy is given off).
The energy absorbed or emitted is exactly equal to the difference in energy levels.
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Page 4
Chapter 3: The Solar System
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Q1) What physical characteristics of Mercury distinguish it among all the planets in our solar system?
Answer: Mercury has the most eccentric orbit of any of the planets. Mercury's orbital plane has the highest inclination to the ecliptic. Mercury is the smallest body considered a planet in the solar system.
Q2) How can astronomers determine the mass of the Sun?
Answer: Using Newton's Laws, we know that gravity keeps the Earth in orbit around the Sun. Since the Earth's path is nearly circular, we can determine the size of the force keeping it on this path. Combining this equation (for centripetal force) with the gravity equation allows astronomers to calculate the Sun's mass.
Q3) Galileo's observations of sunspots proved the Sun was rotating, like the Earth. A)True
B)False
Answer: True
Q4) While both Ptolemy and Copernicus assumed all orbits were ________, Kepler's first law corrected this and made planetary motion predictable. Answer: circles
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Chapter 4: Earth and Its Moon
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Q1) Why did the Moon's internal heat escape more rapidly than Earth's?
Q2) The average rate of erosion on the Moon is far less than on Earth because A) the crust of the Moon is much denser than the Earth's crust.
B) the Moon is much younger than the Earth.
C) the Moon lacks wind, water and an atmosphere.
D) the Moon's magnetic field protects it from the solar wind better than ours does.
E) the Moon's mare long ago dried up, so there is no more wave erosion there.
Q3) Name the four layers of the Earth's atmosphere, going up from the surface.
Q4) The partial trapping of solar radiation is known as the ________.
Q5) Infrared radiation is trapped close to our surface by the greenhouse effect.
A)True
B)False
Q6) What is the primary source of erosion on the Moon today?
Q7) The ozone layer lies in the mesosphere.
A)True
B)False
Q8) List the six main regions of the Earth, in order, starting from the center.
Page 6
Q9) What layers of the Earth's structure are not present in the Moon's structure?
Q10) Which side of the Moon has the thicker crust? Why?
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Chapter 5: The Eight Planets
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Q1) Why does Saturn radiate even more excess energy than Jupiter?
A) Saturn is still radiating heat left over from its formation.
B) Saturn's thick cloud layer contributes to a larger greenhouse effect.
C) Helium rain gives off heat as it differentiates toward Saturn's center.
D) Saturn's atmosphere contains much methane, creating a large greenhouse effect.
E) Saturn can fuse hydrogen into helium in its core, like the Sun.
Q2) The most striking and largest valley in the solar system is
A) the Grand Canyon in Arizona.
B) Gwenivere on Venus.
C) the Discovery Scarp of Mercury.
D) Valles Marineris on Mars.
E) Valhalla on Callisto.
Q3) Venus' clouds are water vapor and are similar to clouds in Earth's atmosphere.
A)True
B)False
Q4) All 4 jovian planets have a layer of molecular hydrogen above a layer of metallic hydrogen.
A)True
B)False
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Chapter 6: Small Bodies in the Solar System
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Q1) One of the discoveries made by the Voyager probes while near Jupiter was
A) Io has a featureless surface that never changes.
B) a thin ring of dust around the equator.
C) the absence of a magnetic field around the giant planet.
D) that the Great Red Spot is uniform and featureless.
E) each of the four large moons produces a strong magnetic field.
Q2) Define Trojan asteroids.
Q3) Why do Saturn's rings exist?
Q4) Small icy bodies in the solar system which travel about the Sun in highly eccentric orbits and come from all directions are ________.
Q5) What are Saturn's rings?
A) A great disk of liquid helium
B) Large rocky boulders moving in orbit around Saturn
C) A glowing, flat magnetospheric auroral display
D) A solid thin disc of material encircling Saturn
E) Small icy particles moving in orbit around Saturn
Q6) What will happen to Triton in the distant future, based on its present orbit?
Q7) At Titan, the weather is driven by phase changes of ________ gas into liquid or solid forms.
Q8) Why were the mass and density of Pluto unknown until Charon was found?
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Chapter 7: Formation of Planetary Systems
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Q1) What is the process of accretion?
A) The separation of materials in a protoplanet by density, with dense material in core
B) Growth of an object by the accumulation of matter
C) The breakup of large objects by violent collisions with other similar-sized objects
D) The period of time during which the Sun swept away all the excess material in the solar nebula
E) The process by which the solar nebula became heated during its collapse
Q2) What is the most important consideration in the "habitable zone" of a planetary system?
Q3) The Kepler mission uses the ________ technique to detect exoplanets.
Q4) Concerning our solar nebula theory, the presence of so many "hot Jupiters" gives us problems with how they can form that close to their star.
A)True
B)False
Q5) The radial velocity method is less likely to detect low mass planets than high mass planets because low mass planets cause smaller ________ fluctuations.
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Chapter 8: The Sun
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Q1) Suppose a large flare is detected optically. How long until radio interference arrives?
A) Simultaneously
B) 8.5 minutes later
C) About 12 hours
D) About four days
E) No relation between the two
Q2) By what mechanism does solar energy reach the Sun's photosphere from the layer just underneath it?
A) Differentiation
B) Ionization
C) Radiation
D) Convection
E) Conduction
Q3) When the chromosphere can be seen during a solar eclipse, it appears
A) invisible.
B) violet.
C) blue.
D) yellow.
E) red.
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Page 10
Chapter 9: Measuring the Stars
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Q1) Eclipsing binaries are the most useful, giving us sizes as well as masses of the pair.
A)True
B)False
Q2) If a star is found by spectroscopic observations to be about 500 parsecs distant, its parallax is
A) 0.2".
B) 0.5".
C) 0.02".
D) 0.002".
E) 0.005".
Q3) How is distance determined to the nearest stars? How far out can this technique be applied? How many stars can be measured in this way?
Q4) Why are spectra of stars different?
Q5) On the H-R diagram, red supergiants like Betelgeuse lie
A) at the bottom left.
B) at the bottom right.
C) at the top left.
D) at the top right.
E) They can't be plotted, for they are not main sequence.
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Chapter 10: Star Formation and Evolution
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Q1) During the hydrogen shell burning phase
A) the star grows more luminous.
B) the star becomes less luminous.
C) helium is burning in the core.
D) the core is expanding.
E) hydrogen is burning in the central core.
Q2) When helium fusion begins in a one solar mass main star, it begins gradually, with this rate slowly increasing over time.
A)True
B)False
Q3) Which of the following is TRUE regarding planetary nebulae?
A) Some are spherical, but most have bipolar structure.
B) They are the result of the mass loss during the main sequence stage of the most massive stars.
C) They are the rings of material surrounding newly formed stars that will eventually form the planetary systems.
D) They are the ejected envelopes of highly evolved brown dwarf stars.
E) They are the coronas surrounding most blue stragglers.
Q4) Why does gravitational contraction halt in collapsing protostars?
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Chapter 11: Stellar Explosions
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Sample Questions
Q1) The average density of neutron stars approaches
A) a million times that of normal matter.
B) a million times that of even a white dwarf.
C) about 10¹ kg/m³, similar to the density of atomic nuclei.
D) about 10¹ times that of water.
E) infinity.
Q2) How do astronomers know that the Crab Nebula is the remains of a supernova?
Q3) The Chandrasekhar mass limit is
A) 0.08 solar masses.
B) 0.4 solar masses.
C) 1.4 solar masses.
D) 3 solar masses.
E) 8 solar masses.
Q4) What is the importance of 1.4 solar masses in stellar evolution?
Q5) Neutron stars have
A) very strong bi-polar magnetic fields.
B) weak or non-existent magnetic fields.
C) periods of days or weeks.
D) monopolar fields that switch polarity every rotation.
E) no relation to pulsars.
Page 13
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Chapter 12: Black Holes
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Q1) Black holes with masses greater than a million solar masses explain the extremely rapidly moving stars and gas in the cores of galaxies.
A)True
B)False
Q2) What explanation does general relativity provide for gravity?
A) Gravity is the result of curved spacetime.
B) Gravity is directly proportional to the mass of the attracting body.
C) Gravity is inversely proportion to the radius of the body.
D) Gravity is the opposite of the electromagnetic force.
E) Gravity can affect only massive particles, not massless photons.
Q3) To explain gravity, general relativity says that matter tends to ________ space in its vicinity.
Q4) Explain how the essential features of special relativity imply that a beam of light from a fast moving spaceship will always be observed to moving at the speed of light.
Q5) The Schwarzschild radius of a black hole is about 3 km per solar mass; it is amazingly linear over a wide range of masses.
A)True
B)False
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Chapter 13: The Milky Way Galaxy
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Q1) Compare the speed of spiral density waves with the orbital speeds of stars in the visible part of the Galactic disk.
Q2) The major problem faced by optical astronomers in trying to deduce the structure of the Milky Way Galaxy is that we can see only a small part of it because of the ________.
Q3) Why do astronomers believe that there is a large black hole, around 4 million times the mass of our Sun, in the Galactic center?
Q4) How old is the Galaxy? How do we know this?
Q5) The rotation curve for our Galaxy shows stars beyond the Sun moving slower than expected.
A)True
B)False
Q6) The period-luminosity relation for Cepheid variables was discovered in 1908 by A) William Herschel. B) Henrietta Leavitt. C) Harlow Shapley. D) Heber Curtiss. E) Edwin Hubble.
Q7) How can Kepler's Third Law be used to estimate the mass of the galaxy?
Page 15
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Chapter 14: Galaxies
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Q1) Giant elliptical galaxies may be the result of ________ in the centers of rich clusters.
Q2) What type of galaxy are the two Magellanic Clouds? How do we know this visually?
Q3) In the Local Group, how might even the Milky Way become a victim?
Q4) Why is light variability a critical issue with the sizes of active nuclei?
Q5) For nearby spirals, their rotation curves help measure both light and dark matter. A)True
B)False
Q6) What lines of evidence show that the Milky Way Galaxy is indeed a spiral galaxy?
Q7) Most galaxies are members of some sort of cluster of galaxies. A)True B)False
Q8) Gravity lensing lets us map the distribution of both visible and dark matter. A)True
B)False
Q9) It is now believed the majority of mass for most galaxies lies in their dark halos. A)True
B)False
Page 16
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Chapter 15: Cosmology and the Universe
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Q1) Describe what occurred during the period of decoupling.
Q2) Before about 50,000 years after the Big Bang the universe was A) radiation dominated.
B) quark dominated.
C) lepton dominated.
D) matter dominated.
E) dark energy dominated.
Q3) The ________ is the observational evidence that the whole universe was once extremely hot and dense, as called for in the Big Bang, but has now expanded and redshifted this energy to much longer wavelengths.
Q4) The cosmic microwave background is the total of all the radio emissions from all the galaxies and quasars in the universe.
A)True
B)False
Q5) The universe was two minutes old when ________ started to form from deuterium fusion.
Q6) Why were elements heavier than helium not produced during the Big Bang?
Q7) What is the cosmic microwave background, and why is it significant?
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Q8) Describe the separation of the superforce and the effect it had on the Universe.