I'd like to show a demonstration of Runge Kutta integration of real systems using examples of interesting multiple stars, where "interesting" means you can see through a small telescope that they are at least double. I've selected three:

  1. Gamma Andromedae (Almach)
  2. Alpha Geminorum (Castor)
  3. Zeta Ursae Majoris (Mizar and Alcor)

How can I find a state vector (set of relative positions and velocities) - or something similar - for these multiple star systems? An open access link (for everyone) would be great, but a journal reference is fine as well if that's what it takes.

Of course the periods are long and there will be uncertainty - I'd just like to use whatever is known and available, for this demonstration.

  • $\begingroup$ simbad.u-strasbg.fr/simbad/… simbad.u-strasbg.fr/simbad/… simbad.u-strasbg.fr/simbad/… and follow-up the measurements and references. $\endgroup$
    – ProfRob
    Mar 18, 2016 at 12:01
  • $\begingroup$ Thanks @RobJeffries, honestly if I could decode those pages, I'd be smart enough to have known where to find them in the first place! I'm looking for an answer that shows me how to find relative positions and velocities, as will other stackexchange users in the future who find this question. $\endgroup$
    – uhoh
    Mar 18, 2016 at 13:48

1 Answer 1


The USNO Sixth Catalog of Orbits of Visual Binary Stars (ORB6) has the orbital elements you need.

  1. $\gamma$ And is WDS 02039+4220
  2. $\alpha$ Gem is WDS 07346+3153
  3. $\zeta$ UMa is WDS 13239+5456

Double star expert Bruce MacEvoy explains orbital elements in maybe enough detail to help you work out some state vectors. My search also turned up a book chapter by Andreas Alzner.

  • $\begingroup$ This is great! Thank you for finding both the information and places where I can read to actually understand and use the information! I've tried the CTIO Multiple Star Catallog as well as the simbad portal linked in the comments below the question, but couldn't understand how to use what's there. $\endgroup$
    – uhoh
    Apr 22, 2016 at 1:27

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .