  The Wide-field Infrared Survey Explorer (WISE) is a powerful tool for finding
nearby brown dwarfs and searching for new planets in the outer solar system,
especially with the incorporation of NEOWISE and NEOWISE-Reactivation data. So
far, searches for brown dwarfs in WISE data have yet to take advantage of the
full depth of the WISE images. To efficiently search this unexplored space via
visual inspection, we have launched a new citizen science project, called
"Backyard Worlds: Planet 9," which asks volunteers to examine short animations
composed of difference images constructed from time-resolved WISE coadds. We
report the discovery of the first new substellar object found by this project,
WISEA J110125.95+540052.8, a T5.5 brown dwarf located approximately 34 pc from
the Sun with a total proper motion of $\sim$0.7 as yr$^{-1}$. WISEA
J110125.95+540052.8 has a WISE $W2$ magnitude of $W2=15.37 \pm 0.09$, this
discovery demonstrates the ability of citizen scientists to identify moving
objects via visual inspection that are 0.9 magnitudes fainter than the $W2$
single-exposure sensitivity, a threshold that has limited prior motion-based
brown dwarf searches with WISE.
