1998 SH2 Reclassified as Comet P/1998 SH2 After 190-Km Orbital Drift Exposed Outgassing
Updated
Updated · Universe Today · Jul 22
1998 SH2 Reclassified as Comet P/1998 SH2 After 190-Km Orbital Drift Exposed Outgassing
3 articles · Updated · Universe Today · Jul 22
Summary
A 380-meter near-Earth object long tracked as an asteroid was redesignated comet P/1998 SH2 after astronomers tied its unexpected motion to comet-like activity.
In August 2025, the object turned up 153 arcseconds—about 190 km—from its predicted position during a 0.02-AU Earth pass, a miss too large to be explained by the Yarkovsky effect.
CFHT and the Very Large Telescope then revealed a faint 20-arcsecond tail, with dust likely released between Aug. 29 and Sept. 7 and peaking weeks after perihelion, suggesting buried ice drove the outgassing.
The study says this is the first case in which cometary nature was inferred from orbital perturbations before being confirmed by imaging.
Researchers say the finding matters for planetary defense because about 285 potentially hazardous near-Earth objects have comet-like orbits, and sudden outgassing can disrupt impact-path forecasts.