Overview

• Researchers report that WD 1647+375 is actively accreting an icy, volatile‑rich planetesimal identified via Hubble’s Cosmic Origins Spectrograph.
• The debris shows a high nitrogen mass fraction of about 5.1% and an oxygen excess near 84%, indicating a water‑rich composition with a water‑to‑rock ratio of roughly 2.45.
• The accretion has persisted for at least 13 years at about 2×10^8 g/s, implying a parent body at least 3 km across and possibly tens of kilometers if the process has lasted far longer.
• The team interprets the composition as most consistent with a fragment of a Kuiper‑belt–analogue dwarf planet, though an interstellar origin cannot be ruled out from chemistry alone.
• The authors describe this as the first unambiguous case of a hydrogen‑atmosphere white dwarf accreting a purely icy body, and plan infrared follow‑up with JWST to search for molecular signatures.