Hubble has done it again. It has captured a hitherto unknown fourth moon of Pluto, the dwarf planet. The three known moons of Pluto are Charon, Nix and Hydra. The fourth one, discovered just recently on 3rd July, 2011, and officially announced today by NASA and SETI, is temporarily known as P4.
Pluto was stripped of its planet tag on 24th August, 2006 and was relegated to the status of dwarf planet’ along with Eris and Ceres. Eris is, in fact, more massive than Pluto.
Charon is the most well-known moon of Pluto and was the only moon discovered till 2005. It is quite large, with a size comparable with Pluto. In 2005, two newer moons were discovered and named Nix and Hydra. It is not known whether this recently discovered moon, P4, was there at the time of the discovery of the previous moons or was captured more recently.
It was due to the wonder called the Hubble Space Telescope that a cold object, tiny in size and moving fast around a very distant body could be photographed. Mark Showalter of SETI Institute in Mountain View, California has this to say:
I find it remarkable that Hubble’s cameras enabled us to see such a tiny object so clearly from a distance of more than 3 billion miles (5 billion km).
The diameter of the new moon is just 8-21 miles, while Charon, by comparison, is a giant at 648 miles. Nix and Hydra are both about 50 miles in diameter.
NASA aims to discover more about the body least known to man with the upcoming New Horizons mission. New Horizons will hope to fly past Pluto in 2015, using inputs from Hubble’s photos to chart out its path.