  We investigate the origin of a nearly pointlike cluster of 5 ultrahigh energy
cosmic rays at RA ~169.2deg and dec ~56.8deg, using Sloan Digital Sky Survey
and other data. No particular source candidates are found near the estimated
source direction, but the direction is exceptional in having a likely merging
pair of galaxy clusters at 140/h Mpc, with an unusually low foreground density.
Large scale shocks or another product of the merging galaxy clusters may
accelerate the UHECRs, or the merging galaxy clusters may be coincidental and
the UHECRs may be accelerated in a rare event of an unexceptional progenitor.
Low magnetic deflections in the foreground void may explain why this is the
only identified pointlike cluster of so many UHECRs.

Astrophysics