1998 SH2 Confirmed as Comet After 28 Years, Gaining P/1998 SH2 Designation
Updated
Updated · Gizmodo · Jul 21
1998 SH2 Confirmed as Comet After 28 Years, Gaining P/1998 SH2 Designation
3 articles · Updated · Gizmodo · Jul 21
Summary
A 28-year tracking effort ended with astronomers confirming 1998 SH2 is a comet after 2025 observations captured a weak but clear tail during its close pass within 2 million miles of Earth.
NASA radar first flagged the mismatch on Aug. 28, 2025, when the object failed to appear where gravity-only models predicted, pointing researchers to nongravitational thrust from venting gas.
Images from the 3.6-meter Canada-France-Hawaii Telescope, the 1.5-meter Danish Telescope and ESO’s 8.2-meter Very Large Telescope provided the evidence needed to reclassify the object as P/1998 SH2.
The study, published in Nature Astronomy, suggests some so-called dark comets may be ordinary comets with tails and comas too faint for most observations.
Researchers said the finding strengthens planetary-defense tracking because comet outgassing can alter near-Earth orbits more than asteroid motion and change impact-risk assessments.