We present individual dynamical masses for the nearby M9.5+T5.5 binary WISE J072003.20 - 084651.2AB , a.k.a .
Scholz ’ s star .
Combining high-precision CFHT/WIRCam photocenter astrometry and Keck adaptive optics resolved imaging , we measure the first high-quality parallactic distance ( 6.80 _ { -0.06 } ^ { +0.05 } pc ) and orbit ( 8.06 _ { -0.25 } ^ { +0.24 } yr period ) for this system composed of a low-mass star and brown dwarf .
We find a moderately eccentric orbit ( e = 0.240 _ { -0.010 } ^ { +0.009 } ) , incompatible with previous work based on less data , and dynamical masses of 99 \pm 6 M _ { Jup } and 66 \pm 4 M _ { Jup } for the two components .
The primary mass is marginally inconsistent ( 2.1 \sigma ) with the empirical mass–magnitude–metallicity relation and models of main-sequence stars .
The relatively high mass of the cold ( \mbox { $T _ { eff } $ } = 1250 \pm 40 K ) brown dwarf companion indicates an age older than a few Gyr , in accord with age estimates for the primary star , and is consistent with our recent estimate of \approx 70 M _ { Jup } for the stellar/substellar boundary among the field population .
Our improved parallax and proper motion , as well as an orbit-corrected system velocity , improve the accuracy of the system ’ s close encounter with the solar system by an order of magnitude .
WISE J0720 - 0846AB passed within 68.7 \pm 2.0 kAU of the Sun 80.5 \pm 0.7 kyr ago , passing through the outer Oort cloud where comets can have stable orbits .