S/2008 (41) 1

A. R. Conrad, W. M. Keck Observatory (WMKO); W. J. Merline, Southwest Research Institute (SwRI); J. D. Drummond, Starfire Optical Range, Air Force Research Laboratory, Kirtland Air Force Base; P. M. Tamblyn, Binary Astronomy, Dillon, CO, and SwRI; C. Dumas, European Southern Observatory (ESO), Chile; B. X. Carry, ESO; R. D. Campbell and R. W. Goodrich, WMKO; W. M. Owen, Jet Propulsion Laboratory; and C. R. Chapman, SwRI, report the discovery on Mar. 28.5 UT of a satellite of minor planet (41) Daphne from more than 100 J-, H-, K-, and K'-band images with the 10-m Keck II telescope (+ NIRC2/AO adaptive-optics system) on Mauna Kea. On Mar. 28.5032, the satellite was at separation 0".56 (projected separation 443 km) and position angle 277 deg. The satellite was observed to be moving with the primary, as they traveled 80" across the background sky over the 3 hours. The significant (0".3) orbital motion of the satellite observed during this time implies an orbital period near 1.6 days. The H-band brightness ratio is estimated at about 10 mag, giving an estimated diameter of the satellite of < 2 km; if so, this system has the most extreme size ratio known (cf. EMP 2008, p. 256).