Orbital Distance (a=AUs)	Orbital Period (P=years)	Orbital Eccentricity (e)	Orbital Inclination (i=degrees)	Mass (Earths)	Diameter (Earths)	Density (Earths)	Surface Gravity (Earths)	Metallicity (Solar)
AB Mass Center	0.0	...	...	...	...	...	...	...	...
Tau Boötis A	30	~2,000	0.91	50.68	420,000	159	...	...	2.09
Planet "b"	0.05	0.009	0.23	44.5	1,900	13	...	...	...
Disrupted H.Z. A?	1.8	2.2	0	44.5	...	...	...	...	...
Tau Boötis B	194	~2,000	0.91	50.68	70,000	63	...	...	...
H.Z. B	0.09	0.06	0	...	...	...	...	...	...

NOTE: This animation attempts to relate the possible orbits of the Tau Boötis AB system (and their habitable zones) to their common center of mass. To enlarge the display, the orbits have been arbitrarily rotated by 135 degrees. Although the initial display shows the AB system's and Star A and its planet's actual orbital tilts (inclination of 50.68° and 44.5°, respectively ) from the visual perspective of an observer on Earth, the orbital inclination of any planet that may be discovered someday around Star B would likely be different from that of Star B's habitable zone orbit depicted here. To "jump" to a close-up animation of the Tau Boötis A planetary system, click here (or on Tau Boötis A in the animation above).

Tau Boötis has a widely separated, dim companion Star ("B") that is located about 224 AUs away on average (a semi-major axis of 14.39" at a HIPPARCOS distance of 50.87 light-years) with an orbital period around 2,000 years, a very high orbital eccentricity of 0.91, and an inclination of 50.68° from the perspective of an observer on Earth (Alan Hale, 1994, see HD 120136; and the Fifth Catalog of Visual Orbits of Binary Stars).

Star A also has a planetary companion "b" with at least 4.1 times Jupiter's mass. Planet b moves around Star A at an average distance of less than 0.05 AUs (a semi-major axis well within Mercury's orbital distance) in a near circular orbit (e=0.02) that takes 3.3 days to complete. This orbit may be inclined by less than 83° from the perspective of an observer on Earth (Baliunas et al, 1997). Assuming a Jupiter-like composition, planet b's radius is projected to be about 1.2 times that of Jupiter, enlarged relative to Jupiter because of greater absorbed stellar radiation in its inner orbit.