Astr 2100 Descriptive Astronomy
Fall 2017 - Assignment 5
due Monday October 23^{rd} 2017
The answers to some of these
questions can be quite involved. Please supply complete answers, including
all your calculations, in case I need to assign partial credit.
To keep Kepler's 3^{rd} Law simple (a³ = P²) then
all distances must be measured in _______________
all times must be measured in _______________
Mercury is about 0.39 AU from the Sun. How many Earth days constitute its
year?
Jupiter is about 5.2 AU from the Sun. How long is its year?
A planet orbits its star at a distance of 5 AU, taking 8 Earth years to
go around once. What is the mass of the star (in solar masses)?
A planet is observed to be orbiting a star of known mass equal to 6 solar
masses. It is observed to make full orbit in 187 days. What is the radius
of the orbit.
Two moons are observed to be orbiting the same planet. Moon A is 3 x 10^{8}
m from the planet, and moon B is 7.5 x 10^{7} m from the planet.
If Moon A takes 11 days to make one orbit, how long does moon B take?