Orbital Distance (a=AUs)	Orbital Period (P=years)	Orbital Eccentricity (e)	Orbital Inclination (i=degrees)	Mass Estimate (Solar)	Diameter (Solar)	Density (Earths)	Surface Gravity (Earths)	Metallicity (Solar)
Aab Mass Center	0.000	...	...	...	...	...	...	...	...
Castor Aa	0.005	0.0252	0.499	?	2.15?	2.3	...	...	<1
Castor Ab	0.017	0.0252	0.499	?	0.65?	<1	...	...	<1
H.Z. Aab	~5.8	8.4	0	?	...	...	...	...	...

NOTE: This animation attempts to relate the orbits and possible habitable zone of stars Aa and Ab in the Castor system to their center of mass. For the purposes of this animation, the masses of stars Aa and Ab are assumed to be 2.3 and 0.6 Solar, respectively. You will need to vastly expand the field of view to see the orbital motion of the two stars around their center of mass.

Stars Aa and Ab have a combined luminosity of over 34 times that of Sol's. They are separated on average by only 0.022 AUs (of a semi-major axis). Their highly eccentric orbit (e= 0.499) takes only 9.21 days to complete (Joel Stebbins, 1914, pp. 465-466; and Heber D. Curtis, 1906). Currently, the circumbinary orbit of an Earth-like planet (with liquid water) around Stars Aab may be centered just beyond 6.0 AU -- just outside the orbital distance of Jupiter in the Solar System. Astronomers would find it very difficult to detect an Earth-type planet in the water zone of any star in this system using present methods.