Electronic Telegram No. 310 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT@CFA.HARVARD.EDU (science) URL http://cfa-www.harvard.edu/iau/cbat.html S/2005 (2003 EL_61) 2 M. E. Brown, California Institute of Technology, on behalf of the adaptive-optics team at Keck Observatory, reports the discovery of a second satellite of the transneptunian object 2003 EL_61 from K'-band images taken with the Laser Guide Star Adaptive Optics system at the Keck II telescope on Mar. 1, May 27, and June 29. The satellite is 4.6 +/- 0.5 mag fainter than the primary. A preliminary circular orbit suggests a 34.1-day period with a semimajor axis of 39300 km, inclined by 40 degrees from the larger outer satellite, S/2005 (2003 EL_61) 1 (cf. IAUC 8577), though additional observations are required to confirm the orbit. Additional information can be found at website http://www.gps.caltech.edu/~mbrown/2003EL61 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2005 CBAT 2005 November 29 (CBET 310) Daniel W. E. Green