* Astronomy

Hubble Discovers a Fifth Moon Orbiting Pluto

A team of astronomers using NASA's Hubble Space Telescope is reporting the discovery of another moon orbiting the icy dwarf planet Pluto. The moon is estimated to be irregular in shape and 6 to 15 miles across. It is in a 58,000-mile-diameter circular orbit around Pluto that is assumed to be co-planar with the other satellites in the system. Provisionally designated S/2012 (134340) 1, the latest moon was detected in nine separate sets of images taken by Hubble's Wide Field Camera 3 on June 26, 27, and 29, 2012 and July 7 and 9, 2012. This discovery increases the number of known moons orbiting Pluto to five.
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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 travelling on a near-circular orbit coplanar 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 P5 interior to Pluto II (Nix) and close to the 1:3 mean motion resonance with Pluto I (Charon).
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Ed ~ it seems the New Horizons team commissioned a further study of Pluto with the HST to avoid any potential damage to the spacecraft passing near Pluto.