In fact Castor is a sextuple star system made of three binaries, bright visual stars Castor Aab and Bab and dim red flare stars YY Geminorum AB, which are much brighter in X-ray wavelengths, all orbiting each other in a complex dance.
Detailed descriptions of the system(s) are here: http://www.solstation.com/stars2/castor6.htm
Here is a first draft of the system based on the descriptions at the above site: Obsolete
You can download the updated version here: my later post on page 2 of this thread.
(I've only modeled the orbital dynamics and elements of the system -- no fancy features, such as flares you might expect to see in the YY Geminorum pair)
Not all orbital elements are well known (on that web-site) so I have calculated missing data from other known or estimated values.
(eg. SemiMajorAxis information has not been provided in all cases, so some of those are calculated from known or estimated mass-ratio's).
Please feel free to check my calcs (and the underlying assumptions) and let me know if you have any issues.
Overview of the system with the AabBab system at top right, and the Cab system (YY Geminorum) at the left:
(These orbit each other about every 10,000 years)
celURL: 20,000,000,000 x faster
Zoom in closer on the AabBab barycenter -- the Bab system is at the top, and the Aab system at the bottom:
(orbital period = 467 years)
celURL: 1,000,000,000 x faster
let's take a closer look at the Aab system to see the individual stars Aa and Ab:
(orbital period = 9.21 days)
celURL: 100,000 x faster
and likewise for the Bab system (Ba and Bb):
(orbital period = 2.93 days)
celURL: 100,000 x faster
and then zoom in on the Cab (YY Geminorum) system to see the 2 red (M) dwarf flare stars:
(orbital period = 19.536 hours !! )
celURL: 10,000 x faster
):
). Once I've discovered the appropriate appmags for each star the luminosity values should be more accurate.