  We report the first direct detection with Spitzer of galaxy filaments. Using
Spitzer and ancillary optical data, we have discovered two filamentary
structures in the outskirts of the cluster Abell 1763. Both filaments point
toward Abell 1770 which lies at the same redshift as Abell 1763 (z=0.23), at a
projected distance of ~13 Mpc. The X-ray cluster emission is elongated along
the same direction. Most of the far-infrared emission is powered by star
formation. According to the optical spectra, only one of the cluster members is
classified as an active galactic nucleus. Star formation is clearly enhanced in
galaxies along the filaments: the fraction of starburst galaxies in the
filaments is more than twice than that in other cluster regions. We speculate
that these filaments are feeding the cluster Abell 1763 by the infall of
galaxies and galaxy groups. Evidence for one of these groups is provided by the
analysis of galaxy kinematics in the central cluster region.
