ASTR 111 Study Guide

  1. Introduction
  2. History of astronomy
  3. The sky, coordinates, star motions, navigating the sky
  4. The seasons
  5. Phases of the Moon, eclipses
  6. The Solar System
  7. Earth, Earth-Moon system
  8. Moon
  9. Mercury
  10. Venus
  11. Mars
  12. Jupiter, Saturn
  13. Uranus, Neptune, Pluto
  14. Other Solar System objects

Introduction & Background Material

  • What is the difference between the solar system, galaxy, and universe?
  • List the planets, in order, from closest to the Sun outward.
  • What is it that defines a science?  Does astronomy qualify?  Astrology?
  • Define an astronomical unit (AU).
  • What is a light year (ly)?  Why is it necessary to have such a unit?
  • How are the AU and ly physically meaningful?
  • How is the parsec defined?
  • Put in order of increasing size: parsec, AU, ly
  • Did the solar system form as a direct result of the Big Bang?

History of Astronomy

  • What is retrograde motion? Why was it important, historically speaking?
  • Describe the evolution from a geocentric to heliocentric model for our solar system.
  • What contribution(s) did Ptolemy, Copernicus, Kepler and Newton make?
  • Be able to discuss Kepler’s three laws of planetary motion.
  • What is Newton’s Law of Gravitation?  Why was it an important discovery?

The Sky, Coordinates, Star Motions, Navigating the Sky

  • Understand the various coordinate systems used in astronomy.
  • Define/explain: celestial sphere, NCP, SCP, celestial equator, ecliptic, equinoxes, solstices
  • Be able to label all of the important points on the Celestial Sphere.
  • What effect does Earth’s rotation have on the motion of stars in the sky?
  • How does your location on Earth affect what you see in the sky?
  • What is precession? How has it impacted our view of the sky?
  • What is the Zodiac?  Why was it important even to early cultures?
  • Explain how constellations differ from asterisms.
  • Discuss how to recognize the Big Dipper, and use it to find 2 other stellar objects.
  • What makes Polaris special?
  • What does Cassiopeia really look like?
  • List the major stars in the Summer Triangle.
  • Describe how to find the Andromeda Galaxy.
  • What does Bootes look like? What is its major star?


  • What is the ecliptic?  Understand BOTH common definitions.
  • What causes seasons on the Earth? What common answer is actually incorrect?
  • Know where the Sun is (as seen from Earth) on solstices & equinoxes.
  • Understand and be able to explain the importance of axial tilt to the seasons.
  • Define/explain: Arctic & Antarctic Circles, Tropics of Cancer & Capricorn
  • Give 2 reasons why are summers warmer than winters in the northern hemisphere.
  • Discuss what conditions might be like on a planet with arbitrary axial tilt.

Phases of the Moon, Eclipses

  • Know the order of the lunar phases; be able to draw them, give rise/set times.
  • Explain the difference between synodic and sidereal periods of the Moon.
  • List the conditions required for both solar and lunar eclipses.
  • Define umbra and penumbra.
  • Be able to discuss the three types of lunar eclipses in detail.
  • Be able to discuss the three types of solar eclipses in detail.
  • Why does the Moon appear red during a total lunar eclipse?
  • Why are eclipses so rare?
  • Why are solar eclipses so short compared to lunar eclipses?

Solar System

  • What is a nebula? A solar nebula?
  • Why are the terrestrial (rocky) planets found closer to the Sun?
  • Describe the time-line of planetary formation from planetesimals to planets.
  • How did planetary formation affect things like the shape of orbits & the ecliptic?
  • What are comets and asteroids?
  • How do we know how old the solar system is?

Earth, Earth-Moon system

  • What is the Earth’s interior like? How do we know?  Describe its layers/make up.
  • What is Plate Tectonics?  What evidence is there for it?
  • How did Earth’s atmosphere originally form? How did it change over time? Why?
  • Be able to discuss the Earth’s magnetic field (origin, shape, function).
  • Why do aurora form?
  • Why do we have tides on the Earth?  What is their impact?
  • Define spring and neap tides.
  • What is synchronous rotation?
  • Explain why the Moon is in synchronous rotation with the Earth.


  • List major surface features on the Moon.
  • What is regolith? How does it differ from soil?
  • Describe the various formation theories for the Moon.
  • What is the interior of the Moon like?  How do we know?


  • How does Mercury differ from the Moon?  List some unique characteristics.
  • Discuss notable surface features and properties of Mercury.
  • Why does Mercury have such a weak magnetic field?


  • Why is Venus so hot?
  • Compare the atmospheres, past and present, of Earth and Venus.
  • Why are there so few craters on Venus?
  • Why do we have so few pictures of the surface of Venus?
  • Be able to explain the Runaway Greenhouse Effect.


  • Why has so much effort been expended on exploring Mars?
  • What are the Martian “canals”?
  • Discuss a few of the major surface features on Mars.
  • Compare Mars’ atmosphere to that of Earth.
  • Did Mars ever have flowing water? What evidence is there?
  • What happened to the water on Mars?  Why?
  • Does Mars have moons? If so, how many & describe their possible origin.

Jupiter & Saturn

  • How big is Jupiter? What is it made of?
  • Why does Jupiter have such a strong magnetic field?
  • What are Jupiter’s belts and zones?
  • What is the Great Red Spot, and why has it survived so long?
  • Name all 4 Galilean moons and a few interesting facts about each.
  • What forms the rings around Saturn?
  • What other planets also have rings?
  • Why is Saturn’s atmosphere less stormy than Jupiter’s?
  • What is interesting about Saturn’s moon Titan?

Uranus, Neptune & Pluto

  • What strange feature does Uranus have compared to the other planets?
  • What gives Neptune its distinctive colour?
  • Compare the outer planets to each other.
  • What is unusual about Pluto?
  • What is Charon?  What makes it unusual?
  • Why is Pluto not a planet?

Other Solar System objects

  • How do asteroids, comets and meteors compare to each other? Differ?
  • Where are most asteroids located?  Comets?
  • What is the difference between meteoroids, meteors, and meteorites?
  • What are the 3 main components of a comet when it is near the Sun?
  • Why do comets develop tails?
  • Are we prepared for a large impact?  Why is this question relevant & important?
  • What happened to the dinosaurs?  Could it happen to us?