NEW SATELLITE OF (134340) PLUTO: S/2011 (134340) 1
M. R. Showalter, SETI Institute; and D. P. Hamilton, University of
Maryland -- on behalf of a team that includes S. A. Stern (Southwest
Research Institute), H. A. Weaver (Applied Physics Laboratory, Johns
Hopkins University), and A. J. Steffl and L. A. Young (Southwest Research
Institute)) -- report the discovery of a new satellite of Pluto. The object,
provisionally designated S/2011 (134340) 1, was detected in five separate
sets of images taken by the Hubble Space Telescope WFC3/UVIS: two sets on
2011 June 28.6 UT, two on July 3.4, and one on July 18.92. The body is
visible in individual 8-minute exposures, and S/N > 5 when the five images
of each set are co-added. On June 28, the satellite was 2".48 from the center
of Pluto in p.a. 335 deg; on July 3, it was 2".01 from Pluto at p.a. 27 deg;
on July 18, it was 2".035 from Pluto at p.a. 198.1 degrees. The satellite's
magnitude is V = 26.1 +/- 0.3, making the object about 10 percent as bright
as Pluto II (Nix). The diameter depends on the assumed geometric albedo:
14 km if p_v = 0.35, or 40 km if p_v = 0.04. The motion is consistent with a
body traveling on a circular, equatorial orbit. The inferred mean motion is
11.2 +/- 0.1 degrees per day (P = 32.1 +/- 0.3 days), and the projected radial
distance from Pluto is 59000 +/- 2000 km, placing the satellite between the
orbits of Pluto II (Nix) and III (Hydra).
