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THE ASTRONOMER Electronic Circular No 2751      2011 Jly 21 19.20UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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NEW SATELLITE OF (134340) PLUTO: S/2011 (134340) 1
M. R. Showalter, SETI Institute et. al., report on CBET 2769 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. On June 28, 
the satellite was 2.48" from the centre of Pluto in PA 335 deg; on July 
3, it was 2.01" from Pluto at PA 027 deg; on July 18, it was 2.035" from 
Pluto at PA 198.1 deg.  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 deg 
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).

Editor: The object has now been found on various archival images, 
usually at about magnitude 25.5-26.0.

Guy M Hurst