We have performed a survey for substellar companions to young brown dwarfs in the Taurus star-forming region using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope .
In these data , we have discovered a candidate companion at a projected separation of 0 \farcs 105 from one of the brown dwarfs , corresponding to 15 AU at the distance of Taurus .
To determine if this object is a companion , we have obtained images of the pair at a second epoch with the adaptive optics system at Gemini Observatory .
The astrometry from the Hubble and Gemini data indicates that the two objects share similar proper motions and thus are likely companions .
We estimate a mass of 5–10 M _ { Jup } for the secondary based on a comparison of its bolometric luminosity to the predictions of theoretical evolutionary models .
This object demonstrates that planetary-mass companions to brown dwarfs can form on a timescale of \tau \lesssim 1 Myr .
Companion formation on such a rapid timescale is more likely to occur via gravitational instability in a disk or fragmentation of a cloud core than through core accretion .
The Gemini images also reveal a possible substellar companion ( \rho = 0 \farcs 23 ) to a young low-mass star that is 12 \farcs 4 from the brown dwarf targeted by Hubble .
If these four objects comprise a quadruple system , then its hierarchical configuration would suggest that the fragmentation of molecular cloud cores can produce companions below 10 M _ { Jup } .