  The Kuiper Belt of our solar system is a source of short-period comets that
may have delivered water and other volatiles to Earth and the other terrestrial
planets. However, the distribution of water and other volatiles in extrasolar
planetary systems is largely unknown. We report the discovery of an accretion
of a Kuiper-Belt-Object analog onto the atmosphere of the white dwarf WD
1425+540. The heavy elements C, N, O, Mg, Si, S, Ca, Fe, and Ni are detected,
with nitrogen observed for the first time in extrasolar planetary debris. The
nitrogen mass fraction is $\sim$ 2\%, comparable to that in comet Halley and
higher than in any other known solar system object. The lower limit to the
accreted mass is $\sim$ 10$^{22}$ g, which is about one hundred thousand times
the typical mass of a short-period comet. In addition, WD 1425+540 has a wide
binary companion, which could facilitate perturbing a Kuiper-Belt-Object analog
into the white dwarf's tidal radius. This finding shows that analogs to objects
in our Kuiper Belt exist around other stars and could be responsible for the
delivery of volatiles to terrestrial planets beyond
