12 July 2012 IAU Circular No.9253 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION New postal address: Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. CBATIAU@EPS.HARVARD.EDU ISSN 0081-0304 URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network ________________________________________ NEW SATELLITE OF (134340) PLUTO: S/2012 (134340) 1 ________________________________________ M. R. Showalter, SETI Institute; H. A. Weaver, Applied Physics Laboratory, Johns Hopkins University; S. A. Stern, A. J. Steffl, M. W. Buie, and W. J. Merline, Southwest Research Institute; M. J. Mutchler and R. Soummer, Space Telescope Science Institute; and H. B. Throop, NASA Headquarters, report the discovery of a fifth satellite of Pluto. The object, provisionally designated S/2012 (134340) 1, was detected in fourteen separate sets of images taken by the Hubble Space Telescope WFC3/UVIS. Each image set comprises eleven to twelve 3-minute exposures. Upon co-adding, S/N = 5-8 in five sets and S/N = 3-5 in nine sets where the detection was somewhat degraded by the satellite's close proximity of Pluto II (Nix). Times and offsets for the new satellite are as follows: June 26.51-26.67 UT, 3 sets, 1".99 from Pluto in p.a. 158 deg; June 27.78-27.94, 3 sets, 1".71 in p.a. 182 deg; June 29.64-29.80, 3 sets, 1".44 in p.a. 219 deg; July 7.42-7.58, 3 sets, 1".76 in p.a. 352 deg; July 9.41-9.51, 2 sets, 1".42 in p.a. 31 deg. The satellite's mean magnitude is V = 27.0 +/- 0.3, making it 4 percent as bright as Pluto II (Nix) and half as bright as S/2011 (134340) 1. The diameter depends on the assumed geometric albedo (10 km if p_v = 0.35, or 25 km if p_v = 0.04). The motion is consistent with a body traveling on a near-circular orbit that is co-planar with the other satellites. The inferred mean motion is 17.8 +/- 0.1 degrees per day (P = 20.2 +/- 0.1 days), and the projected radial distance from Pluto is 42000 +/- 2000 km, placing S/2012 (134340) 1 interior to Pluto II (Nix) and close to the 1:3 mean motion resonance with Pluto I (Charon). ________________________________________(38628) HUYA ________________________________________ K. S. Noll, Goddard Space Flight Center, NASA; W. M. Grundy, Lowell Observatory; H. Schlichting, University of California, Los Angeles; R. Murray-Clay, Center for Astrophysics; and S. D. Benecchi, Department of Terrestrial Magnetism, Carnegie Institution, report the detection of a binary companion to (38628) = 2000 EB_173. Observations started on May 06.02842 UT with the Wide Field Camera 3 on the Hubble Space Telescope (HST). Two dithered observations were made in each of two filters, F606W and F814W. A secondary, approximately 1.4-mag fainter than the primary, can be seen in each image located at a separation relative to the primary of -0".0875 +/- 0".0017 in R.A. and +0".0272 +/- 0".0013 in Decl. Reexamination of archival data shows evidence of the unresolved secondary in images obtained with the HST Imaging Spectrograph instrument on 2002 June 30.81257 and 2002 July 01.61459. 2012 July 12 (9253) Daniel W. E. Green