Download SCI 103

SCI 103 Jaquin’s Sections
03/14/14
Second Astronomy Exam:
The Copernican Revolution and Gravity.
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1. The ancient Ptolemaic astronomers had deduced an order for the
planets as one proceeded away from the Earth towards the stellar
sphere. See figure to the right. On which of the following
apparent properties of the planets was this order based upon?
a. Apparent Magnitudes of the Planets (i.e. their brightness)
b. Maximum elongation angles
c. Periods of retrograde motion
d. Time to cycle the zodiac
e. Their mythological hierarchy
2. On the diagram to the right label the deferent, epicycle and equant.
3. Where is a planet on its epicycle when it goes retrograde? Why does it
go retrograde only when it is on that part of its epicycle? Answer in a
sentence or two.
4. Why was an equant necessary in the Ptolemaic model? Illustrate with an example. Answer in a few
sentences.
5. In 1543 Copernicus proposed that the Earth was a planet. What motions did Copernicus attribute to the
Earth? Be complete in your answer. Answer in a few sentences.
6. In a sentence or two explain how the modern Copernican model of the Universe explains why inferior
planets have a maximum elongation.
7. In a sentence or two explain how the modern Copernican model of the Universe explains the occurrence
of retrograde motion coincident with opposition and brightening for the superior planets.
8. The figure to the right illustrates Copernicus’ original heliocentric
model of the Solar System. As you can see it is quite complex
compared to the simpler model we use today. What two flaws in the
original Copernican model created this complexity? Answer in a
sentence.
9. Kepler’s first two Laws of Planetary Motion contradicted the Aristotelian/Ptolemaic Model of the
Universe in two fundamental ways. State Kepler’s first two Laws of Planetary Motion and how were
they anti-Aristotelian? Use appropriate vocabulary. Answer in a few sentences.
The figure below is an ellipse. The axes are marked in units of AUs. The position of the Sun is marked.
Answer the questions that appear below the figure by filling in the blanks.

10. What is the semi-major axis of this ellipse in AU? ______________
11. What is the perihelion distance of this orbit in AU _______________
12. What is the aphelion distance of this ellipse in AU? ______________
13. What is the eccentricity of this ellipse? ____________
14. The asteroid 1981 Midas was discovered on March 6, 1973 by Charles T. Kowal at Palomar
Observatory. Its orbital semi-major axis is 1.78 AU. What is its orbital period in days? Show your work
to solve the problem below.
15. 6063 Jason (1984 KB) is an Apollo asteroid discovered on May 27, 1984 by Carolyn and Eugene
Shoemaker at Palomar. Its perihelion and aphelion distances are 0.525 AU and 3.91 AU respectively.
What is Jason’s orbital semi-major axis?
16. Please choose one of Galileo’s telescopic observations of the Moon, the Sun, or Jupiter and briefly
describe what he saw and how it contradicted the Aristotelian Model of the Universe. Be complete in
your answer. Answer in a few sentences.
17. The figure below is a reproduction of Galileo’s record of observations of Venus from Il Saggiatore
[The Assayer] Rome, 1623. What is it about Galileo’s Venus observations that was so damaging to the
Aristotelian/Ptolemaic Model of the Universe? Answer in a few sentences.
18. The Universal Gravitational constant G is an extremely small number equal to 6.6710-11 in mks units.
What does it mean that G is so small? What would the universe, or daily life, be like if G were a
number closer to one? Answer in a few sentences below.
19. If Neptune was 1.0 A.U. from the Sun (instead of 20 A.U.), would the gravity force between Neptune
and the Sun be less or more than it is now? By how many times?
20. A star designated as BD +48 738 is known to have a planet orbiting it. The mass of the planet is about
289 Earth masses and orbits exactly 1.00 AU from the star. The mass of the star is 0.74 times the mass
of the Sun. Which of the statements below regarding the time this planet takes to orbit the star true?
Circle the correct answer.
a.
b.
c.
d.
The planet takes one year to circle the star because it is 1 AU from it.
The planet takes longer than one year to circle the star because it is so massive.
The planet takes less than one year to circle the star because it is so massive.
The planet takes longer than one year to circle the star because the star is less massive than the
Sun.
e. The planet takes less than one year to circle the star because the star is less massive than the Sun.
The figure below shows four identical stars and four planets of various masses in circular orbits of various
sizes. In each case the mass of the planet is given in Earth masses and the orbital distance is given in
Astronomical Units (AU). Note that the sizes of the stars and the orbital distances have not been drawn to
scale.
21. Which of the following is the best possible ranking for the period of the orbit of these planets orbiting
Two Earth Masses
One Earth Mass
Three Earth Masses
1 AU
A
A
One Earth Mass
2 AU
1 AU
2 AU
C
C
BB
D
D
from shortest to longest?
a.
b.
c.
d.
e.
D<C<B<A
A = C < B =D
A=B<C<D
A < C < B <D
A=B=C=D
22. The image to the right is of an asteroid named Ida and its tine satellite
named Dactyl (That’s right – an asteroid with a moon!) What would and
astronomer need to know about this Ida-Dactyl system to calculate the
mass of the asteroid Ida? Answer in a few sentences.
23. An asteroid is observed by a student astronomer with their
telescope. The asteroid is at opposition on January 1 and
then again at opposition exactly 15 months later. See the
figure. Calculate the orbital period of the asteroid in years.
1st Opposition



2nd Opposition
24. The Voyage I spacecraft launched in the mid-1970’s is currently19 Trillion km from the Sun. If the AU
were shrunk to 1 foot, how far away would the Voyager I be from the Sun?