Ultraviolet images taken with the Hubble show the location of P4.

Astronomers using the Hubble Space Telescope have discovered another moon orbiting Pluto, joining the ranks of Pluto’s three other known moons. The largest, Charon, was discovered in 1978 at the U.S. Naval Observatory in Flagstaff. The existence of two other moons — Hydra and Nix — was confirmed using the Hubble telescope in 2005. The newly-discovered moon has been given the tentative name P4. (Presumably the discoverers or the IAU will come up with something more interesting once a little more is known about it. I offer ‘Zaphod’ as a candidate. It’s about time we started introducing ephemeral pop culture to outer space.)

Incidentally, Pluto is the only member of the original nine-planet system that has not been explored by an Earth probe; but that will change in 2015 when the New Horizons probe, launched in 2006, flies by to study the dwarf planet and its four (known) moons.

Recommended reading:

• NASA: Pluto
• NASA: New Horizons Web Site