  Near-infrared photometric observations of the Type IIn SN 2005ip in NGC 2906
reveal large fluxes (>1.3 mJy) in the K_s-band over more than 900 days. While
warm dust can explain the late-time K_s-band emission of SN 2005ip, the nature
of the dust heating source is ambiguous. Shock heating of pre-existing dust by
post-shocked gas is unlikely because the forward shock is moving too slowly to
have traversed the expected dust-free cavity by the time observations first
reveal the K_s emission. While an infrared light echo model correctly predicts
a near-infrared luminosity plateau, heating dust to the observed temperatures
of ~1400-1600 K at a relatively large distance from the supernova (> 10^{18}
cm) requires an extraordinarily high early supernova luminosity (~1 X 10^{11}
L_solar). The evidence instead favors condensing dust in the cool, dense shell
between the forward and reverse shocks. Both the initial dust temperature and
the evolutionary trend towards lower temperatures are consistent with this
scenario. We infer that radiation from the circumstellar interaction heats the
dust. While this paper includes no spectroscopic confirmation, the photometry
is comparable to other SNe that do show spectroscopic evidence for dust
formation. Observations of dust formation in SNe are sparse, so these results
provide a rare opportunity to consider SNe Type IIn as dust sources.
