We present the identification of two previously known young objects in the solar neighbourhood as a likely very wide binary .
TYC 9486-927-1 , an active , rapidly rotating early-M dwarf , and 2MASS J21265040 - 8140293 , a low-gravity L3 dwarf previously identified as candidate members of the \sim 45 Myr old Tucana Horologium association ( TucHor ) .
An updated proper motion measurement of the L3 secondary , and a detailed analysis of the pair ’ s kinematics in the context of known nearby , young stars , reveals that they share common proper motion and are likely bound .
New observations and analyses reveal the primary exhibits Li 6708 Å absorption consistent with M dwarfs younger than TucHor but older than the \sim 10 Myr TW Hydra association yielding an age range of 10-45 Myr .
A revised kinematic analysis suggests the space motions and positions of the pair are closer to , but not entirely in agreement with , the \sim 24 Myr old \beta Pictoris moving group .
This revised 10-45 Myr age range yields a mass range of 11.6–15 M _ { J } for the secondary .
It is thus likely 2MASS J2126 - 8140 is the widest orbit planetary mass object known ( > 4500AU ) and its estimated mass , age , spectral type , and T _ { eff } are similar to the well-studied planet \beta Pictoris b .
Because of their extreme separation and youth , this low-mass pair provide an interesting case study for very wide binary formation and evolution .