The measured proper motion of Fornax , expressed in the equatorial coordinate system , is ( \mu _ { \alpha } , \mu _ { \delta } ) = ( 47.6 \pm 4.6 , -36.0 \pm 4.1 ) mas century ^ { -1 } .
This proper motion is a weighted mean of four independent measurements for three distinct fields .
Each measurement uses a quasi-stellar object as a reference point .
Removing the contribution of the motion of the Sun and of the Local Standard of Rest to the measured proper motion produces a Galactic rest-frame proper motion of ( \mu _ { \alpha } ^ { \mbox { \tiny { Grf } } } , \mu _ { \delta } ^ { \mbox { \tiny { Grf } } } ) = ( 24.4 \pm 4 % .6 , -14.3 \pm 4.1 ) mas century ^ { -1 } .
The implied space velocity with respect to the Galactic center has a radial component of V _ { r } = -31.8 \pm 1.7 km s ^ { -1 } and a tangential component of V _ { t } = 196 \pm 29 km s ^ { -1 } .
Integrating the motion of Fornax in a realistic potential for the Milky Way produces orbital elements .
The perigalacticon and apogalacticon are 118 ( 66 , 137 ) kpc and 152 ( 144 , 242 ) kpc , respectively , where the values in the parentheses represent the 95 % confidence intervals derived from Monte Carlo experiments .
The eccentricity of the orbit is 0.13 ( 0.11 , 0.38 ) , and the orbital period is 3.2 ( 2.5 , 4.6 ) Gyr .
The orbit is retrograde and inclined by 101 ^ { \circ } ( 94 ^ { \circ } , 107 ^ { \circ } ) to the Galactic plane .
Fornax could be a member of a proposed “ stream ” of galaxies and globular clusters , however the membership of another proposed galaxy in the stream , Sculptor , has been previously ruled out .
Fornax is in the Kroupa-Theis-Boily plane that contains eleven of the Galactic satellite galaxies , but its orbit will take it out of that plane .