Exoplanet Formation
Possible exocomets may be moving volatile material through PDS 70
Rapidly changing sodium absorption around a young planetary system is most consistent with sublimating star-grazing planetesimals, researchers report.
Briefed August 25, 2026 · Aliens in the Clouds
Peer-Reviewed Research
A Nature Communications paper published August 24 reports strongly variable neutral-sodium absorption in archival HARPS spectra of the young PDS 70 system. The lines changed from day to day in number, strength, and radial velocity. The authors argue that sublimating, star-grazing planetesimals are the most plausible explanation for the pattern.
PDS 70 contains two confirmed forming planets and an inner water-vapor reservoir previously observed by Webb. The exocomet interpretation could help explain how volatile material moves into planet-forming regions, but it remains an interpretation requiring follow-up. The study does not prove that these bodies supplied the system's observed water or that any planet there is habitable.
Why it matters
The work offers a testable look at how young planetary systems may redistribute water-building material before worlds finish forming.
What the source establishes
Peer-reviewed result: the sodium variability is measured. Plausible but not final: sublimating exocomets are the source and are delivering the observed water reservoir.
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