By definition , brown dwarfs never reach the main-sequence , cooling and dimming over their entire lifetime , thus making substellar models challenging to test because of the strong dependence on age .
Currently , most brown dwarfs with independently determined ages are companions to nearby stars , so stellar ages are at the heart of the effort to test substellar models .
However , these models are only fully constrained if both the mass and age are known .
We have used the Keck adaptive optics system to monitor the orbit of HD 130948BC , a brown dwarf binary that is a companion to the young solar analog HD 130948A .
The total dynamical mass of 0.109 \pm 0.003 M _ { \odot } is the most precise mass measurement ( 3 % ) for any brown dwarf binary to date and shows that both components are substellar for any plausible mass ratio .
The ensemble of available age indicators from the primary star suggests an age comparable to the Hyades , with the most precise age being 0.79 ^ { +0.22 } _ { -0.15 } Gyr based on gyrochronology .
Therefore , HD 130948BC is unique among field L and T dwarfs as it possesses a well-determined mass , luminosity , and age .
Our results indicate that substellar evolutionary models may underpredict the luminosity of brown dwarfs by as much as a factor of \approx 2–3 \times .
The implications of such a systematic error in evolutionary models would be far-reaching , for example , affecting determinations of the initial mass function and predictions of the radii of extrasolar gas-giant planets .
This result is largely based on the reliability of stellar age estimates , and the case study of HD 130948A highlights the difficulties in determining the age of an arbitrary field star , even with the most up-to-date chromospheric activity and gyrochronology relations .
In order to better assess the potential systematic errors present in substellar models , more refined age estimates for HD 130948A and other stars with binary brown dwarf companions ( e.g. , \epsilon Ind Bab ) are critically needed .