I've developed an n-body orbital mechanics simulator that allows you to explore the solar system with a propulsion system of your choice (Saturn V, Falcon 9 and so on). The orbital state vectors that I use for simulating the orbits of the planets and their moons are obtained for JPL, and it all works pretty well provided you employ a time step that is appropriate for the system being simulated. You can perform a trans-lunar injection, hohmann transfer to get to Mars and so on.

Now, I've heard that a planet has been discovered around Proxima Centauri and not knowing any better, I would of course like to simulate a mission to this planet with a propulsion system of immense power that I have dreamt up with little concern for what can actually be achieved (toying with the idea of using the sun for a gravitational sling-shot, although I'm way too ignorant when it comes to orbital mechanics to know if this would actually work out, disregarding the fact that no known materials would survive the heat and tidal forces a spacecraft would experience in such close proximity to the sun).

Problem, though, is that I don't have any state vectors for the centauri system... You know; x, y, z, vx, vy, vz. Nor do I have state vectors for the path the bary center of our solar system takes through interstellar space. Any chance somebody could point me to a source containing these vectors or alternatively a way to calculate them from the stellar catalogues that are out there (haven't been able to find such catalogues with vector data, but then again I might have looked in the wrong place, in which case I apologise for wasting your time)?


  • $\begingroup$ Congratulations for taking that challenge. Do you employ variable timestep? $\endgroup$
    – Andreas
    Commented Oct 28, 2016 at 14:23
  • $\begingroup$ @Andreas No, at the moment I employ a symplectic iterator with a fixed time step. I originally developed the algorithm for long-term simulations of our solar system (like watching the centaurs get perturbed over time by the gas giants), but I'm starting to realize that I'd better figure out a way of incorporating a variable time step, especially if I want to swing by the sun and then into interstellar space. I'm in the process of porting my simulator to JavaScript so that others can have fun with it; might put my efforts on Github if I find time to clean up the code!!! $\endgroup$ Commented Nov 3, 2016 at 11:54

1 Answer 1


You need a designator first for the celestial body. There are multiple alamacs with different designators, so you may want to note all designators for Proxima Centauri that you can find. "alpha Centauri C" (the Flamsteedt Bayer designator) is a good start.

With these designators, search in public almanacs. You will find your star in bright stars in the navies astronomical almanac or in SIMBAD. Wikipedia also has links to these databases.

You will typically find right ascension and declination in the ICRS reference frame there, together with values for proper motion and radial velocity. These are polar coordinates and rates, you will need to convert them to euclidian coordinates.

All these values are not known with a precision that would allow for a travel without (many) midcourse observations and corrections, a problem that already exists for missions to smaller bodies in our solar system (confer "approach phase" of Rosetta mission). The Gaia mission will improve precision a little bit, but your state vector will include a good amount of guessing.

  • $\begingroup$ Thank you, Andreas, for your input! I'm starting to realize, though, that there are so many variables that I have to take into account if I want the simulation to be even remotely realistic, such as the gravitational tides of the Milky Way and so on. There's no way I'll be able to accomplish this without making a considerable amount of guestimates, but that doesn't take away from the fun! $\endgroup$ Commented Nov 3, 2016 at 11:44
  • $\begingroup$ @HappyKoala You're welcome. Targeting stars is really pioneer work. NASA's Pioneer 11 is roughly targeting lambda Aquilae but will of course never hit. I would be curious if there are any lessons learned from Pioneers trajectory, but if you think about it, the most accurate position estimate comes from earth, not from the probe itself. $\endgroup$
    – Andreas
    Commented Nov 3, 2016 at 11:57
  • $\begingroup$ Yea, would be interesting to learn more about how Project Starshot plans on getting to the Centauri system. Need to do some digging and see if they have published anything on that matter! I just know they are going to accelerate this little nano probe to 20% the speed of light with a HUGE FREAKING LASER (sorry, had to) to get it there, but that's about it! $\endgroup$ Commented Nov 3, 2016 at 12:03
  • $\begingroup$ @HappyKoala Oh, I was not aware of that one! I can image many great SX.SE questions can be asked on this ... $\endgroup$
    – Andreas
    Commented Nov 3, 2016 at 12:07
  • $\begingroup$ @HappyKoala OK, there are already a bunch of question. Never stumbled upon them. I did not find anything on interstellar trajectory planning. $\endgroup$
    – Andreas
    Commented Nov 3, 2016 at 12:12

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