1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Orbit of a comet

  1. Nov 22, 2006 #1
    If I have the eccentricity and the perihelion of an orbit given, how can I compute the aphelion?
     
    Last edited: Nov 22, 2006
  2. jcsd
  3. Nov 22, 2006 #2
    You need to think of what angles correspond the the perihelion and aphelion. Then use the relation between r, e, theta and l to get the aphelion.
     
  4. Nov 22, 2006 #3
    Can I not just use the relation for an ellipse:

    [tex]e = \frac{d}{a}[/tex]

    where d is the distance from the focal point to the center and a is the semi major axis?
     
  5. Nov 22, 2006 #4
    Well yes if you know a and d. You'd get the same result. You might need J as well though.
     
  6. Nov 22, 2006 #5
    I just used the radial equation

    [tex]r_a = \frac{a(1 - e^2)}{1 + e \cos \pi} = a(1+e)[/tex]

    This leads to

    [tex] r_a = \frac{r_p(1+e)}{1-e}[/tex]

    where I have used that

    [tex]a = \frac{r_a + r_p}{2}[/tex]

    But for [tex]r_p = 0,2301 AU[/tex] I get [tex]r_a = 2988 AU[/tex] and this is wrong. I should get [tex]r_a =4699 AU[/tex]. Am I too tired or what is this?
    I have that [tex]e = 0,999846[/tex]
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?