A candidate extrasolar planet companion to the young brown dwarf 2MASSW J1207334-393254 ( 2M1207 ) was recently discovered by Chauvin et al .
They find that 2M1207 B ’ s temperature and luminosity are consistent with being a young , \sim 5 M _ { Jup } planet .
The 2M1207 system is purported to be a member of the TW Hya association ( TWA ) , and situated \sim 70 pc away .
Using a revised space motion vector for TWA , and improved proper motion for 2M1207 , I use the moving cluster method to estimate the distance to the 2M1207 system and other TWA members .
The derived distance for 2M1207 ( 53 \pm 6 pc ) forces the brown dwarf and planet to be half as luminous as previously thought .
The inferred masses for 2M 1207 A and B decrease to \sim 21 M _ { Jup } and \sim 3-4 M _ { Jup } , respectively , with the mass of B being well below the observed tip of the planetary mass function and the theoretical deuterium-burning limit .
After removing probable Lower Centaurus-Crux ( LCC ) members from the TWA sample , as well as the probable non-member TWA 22 , the remaining TWA members are found to have distances of 49 \pm 3 ( s.e.m . ) \pm 12 ( 1 \sigma ) pc , and an internal 1D velocity dispersion of 0.8 ^ { +0.3 } _ { -0.2 } km s ^ { -1 } .
There is weak evidence that the TWA is expanding , and the data are consistent with a lower limit on the expansion age of 10 Myr ( 95 % confidence ) .