Posted by Liz on .
if a comet is 125 years from sun and has a perihelion distance of 1. AU..What is the aphelion distance?
I formulated it this way, is this right?
125years^2/1.AU^3= 15,625

astronomy 
Liz,
my book tells me the answer is 49 AU. I am just not getting the calculation. Please help

astronomy 
drwls,
I explained this yesterday. The distance that gets used in the Kepler equation is the semimajor axis, a, NOT the perihelion distance. Therefore
125^2/a^3 = 1
a^3 = 125^2 = 15625
a = cube root of 15625 = 25 AU
(Aphelion + Perihelion)/2 = a
(Aphelion + Perihelion) = 50
Aphelion = 50  1 = 49 AU 
astronomy 
Liz,
yes this is explained much better thank you for your time