  We report the discovery of a probable dwarf galaxy colliding with NGC 1232.
This collision is visible only in the X-ray spectral band, and it is creating a
region of shocked gas with a temperature of 5.8 MK covering an impact area 7.25
kpc in diameter. The X-ray luminosity is 3.7 x1038ergs s-1. The long lifetime
of this gas against radiative and adiabatic cooling should permit the use of
the luminous afterglow from such collisions to be used as a way of estimating
their importance in galaxy evolution.
