Overview

• Webb’s Aug. 6 spectra, released Aug. 25, show a carbon dioxide–dominated coma with a CO2/H2O mixing ratio of about 8±1, among the highest seen in a comet.
• NASA’s SPHEREx measured CO2 production at roughly 9.4×10^26 molecules per second (about 69 kg/s) and set tight upper limits on water and carbon monoxide.
• Hubble imaging from July 21 constrains the nucleus to no more than 5.6 km across and reveals a dust-bright coma without a prominent classical tail.
• Archival detections from TESS and the Vera Rubin Observatory trace the object back to early May, indicating distant activity likely driven by hypervolatiles.
• The comet will reach perihelion near 1.4 AU on Oct. 29–30 before a Dec. 19 closest Earth distance of about 1.8 AU; speculative artificial‑origin claims remain disputed by most researchers.