Pluto (Dwarf Planet)

Video still: HST Image of Pluto
270 degrees Longitude
Credit: NASA, ESA, and M. Buie
(Southwest Research Institute)

Overview

Pluto, formerly known as the tenth planet, is now regarded as a dwarf planet residing in the Kuiper Belt.

With an apparent magnitude of between +13 and +15 it is impossible to see Pluto with the naked eye, binoculars or anything but a large telescope although with modern telescopes and CCD cameras it is not out of the realms of possibility for the experienced amateur to study Pluto and for that reason many astronomy magazines have started to include Pluto's position in monthly tables.

Natural Satellites

Image: Illustration of the Pluto Satellite System orbits with
newly discovered moon P4 highlighted.
Credit: NASA, ESA, and A. Feild (STScI)
Click here to view original image

Pluto has four known satellites, Charon (the largest), Nix, Hydra and P4.

Charon

Charon, named after the mythical figure who ferried lost souls to the underworld, was discovered in 1978 by astronomer James Christy. With an equatorial radius of 593km it is the largest of Pluto's moons.

Nix

A small moon around 32 to 113km in diameter which lies beyond the orbit of Charon. It was discovered in 2005 by the Hubble Space Telescope.

P4 (S/2011 P 1 or S/2011 (134340) 1)

P4 is a provisional name given the the fourth moon to be found orbiting the dwarf plant pluto. It is a small moon around 13 to 34km in diameter which lies between the orbits of Nix and Hydra. It was discovered in 2011 by the Hubble Space Telescope.