WD 1425+540 (G200-39) is a white dwarf that accreted an exocomet (exo-Kuiper Belt Object, exo-KBO).

[7] The white dwarf is the prototype of the DBA spectral type that indicates both hydrogen and helium in its atmosphere, which was discovered in 1977.

[1] Observations with Keck and Hubble, published in 2017, showed that the white dwarf is polluted with the elements carbon, nitrogen, oxygen, magnesium, silicon, sulfur, calcium, iron and nickel.

The presence of water ice in the accreted body could also explain the high amount of hydrogen in the atmosphere of WD 1425+540.

When the star lost mass during the asymptotic giant branch stage, the Kuiper-Belt analogue would have expanded to beyond 300 au.