ASTR 205 Exam 2 2025 WITH ALL
ANSWERS
-CORRECT ANSWERS✔✔What are planetary rotation and orbital revolution? (explain using a diagram)
Inner: Mercury, Venus, Earth, Mars. Outer (Jovian): Jupiter, Saturn, Uranus, and Neptune; the Asteroid
Belt-CORRECT ANSWERS✔✔Which planets are considered inner or outer planets? What is the region
called that separates them?
Terrestrial: Mercury, Venus, Earth, and Mars; Jovian: Jupiter, Saturn, Uranus, and Neptune; Gas Giants:
Jupiter and Saturn; Ice Giants: Uranus and Neptune-CORRECT ANSWERS✔✔What planets are
considered terrestrial? Jovian? Gas Giants? Ice giants?
The ellipse becomes a circle-CORRECT ANSWERS✔✔If the foci of an ellipse are directly on top of each
other, what happens to the ellipse?
All planets revolve around the sun in elliptical orbits with the sun at one foci-CORRECT ANSWERS✔✔
Kepler's First Law
The straight line connecting the sun and a planet will sweep out equal areas in equal time intervals.
Equation:
, t12=t34
A12=A34-CORRECT ANSWERS✔✔Kepler's Second Law
The cube of the semi-major axis (a) in astronomical units is equal to the square of the period of
revolution (p) in earth years
Equation:
a^3=P^2-CORRECT ANSWERS✔✔Kepler's Third Law
Astronomical Units (AU) (average Earth - Sun distance)-CORRECT ANSWERS✔✔What units are the
semi-major axis (a) and orbital period (p) in for Kepler's third law, a^3=p^2, to be true?
This tells us planets that are further from the sun travel at slower speeds and that planets that are closer
to the sun travel at faster speeds; planets travel the fastest speed in their orbit when at perihelion and
they travel the slowest speed in their orbit when at aphelion-CORRECT ANSWERS✔✔What does the
equation Speed of planet = Sqrt(G*Mass of sun/distance of sun-planet) tell us? What assumption did we
make to derive this formula?
A planet moves fastest at perihelion. It moves slowest at aphelion-CORRECT ANSWERS✔✔At what
point in a planets orbit does it move the fastest? Slowest?
Objective: the material used to gather light; Aperture: the size (in diameter) of objective-CORRECT
ANSWERS✔✔What is a telescope objective? What does the aperture tell you?
Newtonian Telescope-CORRECT ANSWERS✔✔What is another name for a reflecting telescope?
Refracting = lens; Reflecting = mirror; Catadioptrics = both lens and mirror-CORRECT ANSWERS✔✔
What type of optic(s) does a refracting telescope use? Reflecting? Catadioptrics?
ANSWERS
-CORRECT ANSWERS✔✔What are planetary rotation and orbital revolution? (explain using a diagram)
Inner: Mercury, Venus, Earth, Mars. Outer (Jovian): Jupiter, Saturn, Uranus, and Neptune; the Asteroid
Belt-CORRECT ANSWERS✔✔Which planets are considered inner or outer planets? What is the region
called that separates them?
Terrestrial: Mercury, Venus, Earth, and Mars; Jovian: Jupiter, Saturn, Uranus, and Neptune; Gas Giants:
Jupiter and Saturn; Ice Giants: Uranus and Neptune-CORRECT ANSWERS✔✔What planets are
considered terrestrial? Jovian? Gas Giants? Ice giants?
The ellipse becomes a circle-CORRECT ANSWERS✔✔If the foci of an ellipse are directly on top of each
other, what happens to the ellipse?
All planets revolve around the sun in elliptical orbits with the sun at one foci-CORRECT ANSWERS✔✔
Kepler's First Law
The straight line connecting the sun and a planet will sweep out equal areas in equal time intervals.
Equation:
, t12=t34
A12=A34-CORRECT ANSWERS✔✔Kepler's Second Law
The cube of the semi-major axis (a) in astronomical units is equal to the square of the period of
revolution (p) in earth years
Equation:
a^3=P^2-CORRECT ANSWERS✔✔Kepler's Third Law
Astronomical Units (AU) (average Earth - Sun distance)-CORRECT ANSWERS✔✔What units are the
semi-major axis (a) and orbital period (p) in for Kepler's third law, a^3=p^2, to be true?
This tells us planets that are further from the sun travel at slower speeds and that planets that are closer
to the sun travel at faster speeds; planets travel the fastest speed in their orbit when at perihelion and
they travel the slowest speed in their orbit when at aphelion-CORRECT ANSWERS✔✔What does the
equation Speed of planet = Sqrt(G*Mass of sun/distance of sun-planet) tell us? What assumption did we
make to derive this formula?
A planet moves fastest at perihelion. It moves slowest at aphelion-CORRECT ANSWERS✔✔At what
point in a planets orbit does it move the fastest? Slowest?
Objective: the material used to gather light; Aperture: the size (in diameter) of objective-CORRECT
ANSWERS✔✔What is a telescope objective? What does the aperture tell you?
Newtonian Telescope-CORRECT ANSWERS✔✔What is another name for a reflecting telescope?
Refracting = lens; Reflecting = mirror; Catadioptrics = both lens and mirror-CORRECT ANSWERS✔✔
What type of optic(s) does a refracting telescope use? Reflecting? Catadioptrics?
