Astronomy Assignment #3: Solar System History and Structure
Your Name______________________________________
This assignment is due on Tuesday, June 30, 2015
Submit this cover sheet with your assignment..
Answer the following Review Questions from Nick Strobel’s AstronomyNotes: Chapter 4: History and Philosophy of
Western Astronomy
Review Questions
1.
2.
3.
4.
5.
What two basic kinds of models have been proposed to explain the motions of the planets?
Why are epicycles needed in Ptolemy's model?
Why was the Ptolemaic model accepted for more than 1000 years?
What is the Copernican model and how did it explain retrograde motion?
Why did Copernicus not know the absolute distance between various planets and the Sun in his model?
Explain what he would have needed to know to get the absolute distances.
6. What were Galileo’s astronomical discoveries and why was he able to make those discoveries? In
particular address his observation of the Moon, Sun, Jupiter and Venus. Explicitly state what he saw,
how he interpreted it and how his interpretation contradicted the prevailing Aristotelian paradigm.
7. Which observation of Galileo finally disproved the Ptolemaic model? How?
8. What evidence is there that the Earth is rotating and that it is revolving around the Sun?
9. What shape are planet orbits and where is the Sun with respect to the orbit?
10. What happens to a planet's orbital speed as it approaches its farthest point from the Sun and as it
approaches its closest point?
11. A moon's closest distance from a planet is 300,000 km and its farthest distance is 500,000 km. What is
the semi-major axis of its elliptical orbit?
12. How is the average distance between a planet and the Sun related to the planet's orbit period?
13. Which planet has a shorter period---one with a large average distance, or one with a small average
distance?
14. What is the semi-major axis of an asteroid orbiting the Sun with a period of 64 years? (Kepler's third law
works for any object orbiting the Sun.)
15. What would be the eccentricity of an asteroid’s orbit if its perihelion distance was 2.5 AU and its
aphelion distance was 3.2 AU?
Instructor Assigned Topic:
This assignment will ask you to write a two paragraph quantitative description of the properties of the Average Terrestrial and
Jovian Planets. The paragraphs must have a parallel structure (quantitative) summarizing the following properties of the Average
Terrestrial and Jovian planet: distance from the Sun in Astronomical Units, density in g/cm 3, mass in Earth masses, radius in Earth
radii, nature of the surface, principle composition and depth (shallow or deep)* of the atmosphere, number of natural satellites,
rotation period in days (Ignore negative signs) and strength of the magnetic field. The information can be obtained from the text
Appendix (See Planetary Tables). Information not in this location may be found in the chapters covering each planet or through the
Internet at http://nssdc.gsfc.nasa.gov/planetary/factsheet/.
Each paragraph should describe the average Terrestrial or Jovian planet using the known properties of the planets in our Solar
System as a guide. Describe the average Terrestrial and Jovian planet and give the range of their characteristics. You will find it
helpful to complete the table on the other side of this page before constructing the summary paragraphs.
*Note: A shallow atmosphere is any atmosphere whose depth is much smaller than the radius of the planet. Shallow atmospheres are characterized by weak vertical
winds and poorly transport heat away from the planet. A deep atmosphere is any atmosphere whose depth is about the same as the radius of the planet. Deep
atmospheres are characterized by strong vertical winds and efficiently transport heat away from the planet.
Table of Planetary Properties
Average
Property
Mercury
Venus
Earth
Distance
from the
Sun in A.U.
1.0
Density in
gm/cm3
5.5
Mass in
Earth
masses
1.0
Radius in
Earth radii
1.0
Nature of
the surface
Rocky, active
volcanoes, plate
tectonics, ¾
covered by water,
Ice at the poles
Depth (Shallow
or Deep) and
composition of
the atmosphere
Shallow,
N 2 & O2
80% & 20%
Number of
natural
satellites
1
Rotation
Period
1 day
Mars
Terrestrial
Planet
Average
Jupiter
Saturn
Uranus
Neptune
Jovian Planet