  While stars are often found in binary systems, brown dwarf binaries are much
rarer. Brown dwarf--brown dwarf pairs are typically difficult to resolve
because they often have very small separations. Using brown dwarfs discovered
with data from the Wide-field Infrared Survey Explorer (WISE) via the Backyard
Worlds: Planet 9 citizen science project, we inspected other, higher
resolution, sky surveys for overlooked cold companions. During this process we
discovered the brown dwarf binary system CWISE J0146$-$0508AB, which we find
has a very small chance alignment probability based on the similar proper
motions of the components of the system. Using follow-up near-infrared
spectroscopy with Keck/NIRES, we determined component spectral types of L4 and
L8 (blue), making CWISE J0146$-$0508AB one of only a few benchmark systems with
a blue L dwarf. At an estimated distance of $\sim$40 pc, CWISE J0146$-$0508AB
has a projected separation of $\sim$129 AU, making it the widest separation
brown dwarf pair found to date. We find that such a wide separation for a brown
dwarf binary may imply formation in a low-density star-forming region.
