  This paper presents new observations of the planet-hosting, visual binary GJ
86 (HR 637) using the Hubble Space Telescope. Ultraviolet and optical imaging
with WFC3 confirms the stellar companion is a degenerate star and indicates the
binary semimajor axis is larger than previous estimates, with a > 28 AU.
Optical STIS spectroscopy of the secondary reveals a helium-rich white dwarf
with C2 absorption bands and Teff = 8180 K, thus making the binary system
rather similar to Procyon. Based on the 10.8 pc distance, the companion has
0.59 Msun and descended from a main-sequence A star of 1.9 Msun with an
original orbital separation a > 14 AU. If the giant planet is coplanar with the
binary, the mass of GJ 86Ab is between 4.4 and 4.7 MJup. The similarity of GJ
86 and Procyon prompted a re-analysis of the white dwarf in the latter system,
with the tentative conclusion that Procyon hosts a planetesimal population. The
periastron distance in Procyon is 20% smaller than in alpha Cen AB, but the
metal-enriched atmosphere of Procyon B indicates that the planet formation
process minimally attained 25 km bodies, if not small planets as in alpha Cen.
