NASA recently published two images, showing the discovery of a new moon of Pluto, Pluto’s fourth moon. These two images, taken six days apart, by NASA's Hubble Space Telescope (HST), show four moons orbiting the distant, icy dwarf planet Pluto. The newly discovered moon (circled), changes position, in the images, due to its orbital motion. It is temporarily designated P4, and was found in June, by HST, which explores the cosmos from Earth orbit.
P4 is the smallest of Pluto’s known moons, with an estimated diameter of 13 to 34 km. Pluto's largest moon, Charon, is 1,200 km across, while Nix and Hydra, Pluto’s other two satellites, are estimated to be 32 to 110 km wide. For comparison, Earth’s Moon is 3,476 km across, while Pluto is approximately 2,300 km wide. P4 orbits between Nix and Hydra, which were also discovered by Hubble, in 2005. It lasts roughly 31 days, to complete an orbit.
P4 was first detected in a photo obtained by HST, on 28 June 2011. Follow-up observations, performed by HST, on 3 July and 18 July, confirmed the presence of P4.
P4, Nix, and Hydra are so small and so faint that scientists combined images, to produce this family picture of Pluto and its moons. The speckled background and linear features are imaging artifacts.
The tiny satellite was spotted in a Hubble survey to search for rings around Pluto. These observations will yield interesting information for NASA's New Horizons spacecraft, en route to Pluto, scheduled to fly by the enigmatic small world, in 2015.
References
Hubble Site
http://hubblesite.org/