Astronomers discover fifth moon of Pluto

While it may have been relegated from its position as a planet, interest in the erstwhile ninth planet of the Solar System, Pluto, has not died down, especially when astronomers have just announced that they have discovered a new moon of the dwarf planet.

Adding to the ranks of the dwarf planet’s four existing moons - Charon, Hydra, Nix and P4 -, astronomers have now detected a new, fifth moon that for the time being goes under the designation of S/2012 (134340) 1 or “P5.”

Using the Hubble telescope, astronomers were able to identify the new moon from a series of pictures taken over the last couple of weeks by the telescope. Irregularly shaped, the moon is between 6 to 16 miles across, making it the smallest of Pluto’s moons and orbits the dwarf planet at a distance of around 30,000 miles, being in the same neat orbits as the other four moons of Pluto.

Mark Showalter from the Seti Institute in Mountain View, US, who helped discover P5, spoke about Pluto’s moons, saying, "The moons form a series of neatly nested orbits, a bit like Russian dolls,” and added that a name would not be put forward for Pluto’s fifth moon until the researchers are certain that the dwarf planet has no other satellites.

In comparison, Pluto’s largest moon, Charon, discovered in 1978, is 650 miles wide, Nix is 28 miles across, Hydra is 37 miles wide and P4, 21. The pair of Nix and Hydra was discovered in 2005, while P4 was discovered only last year. The new addition of P5 had Hal Weaver of Johns Hopkins University remark, "We're not finished searching yet."

Alan Stern of the Southwest Research Institute in Boulder, Colorado, also commented on P5’s discovery, saying, “The Hubble Space Telescope made very deep, deep images to look for faint satellites of Pluto. This moon is much fainter than others found before. It’s more than a million times fainter than Pluto itself. And Pluto is a million times fainter than anything you can see with your eye.”

The discovery of P5 has thrown up a number of questions, particularly as to how Pluto’s moons formed and how this discovery will affect the NASA New Horizons mission. It is believed that much like Pluto itself, the moons were created from a collision between the dwarf planet and an equally icy celestial body billions of years ago. Alan Stern commented, “This new moon is really telling us something about the origin event that created Pluto’s small moons. It might have been some sort of titanic collision between Pluto and some other rogue planet in the ancient past of our solar system. But we haven’t figured all that out. We’re just at the beginning days of doing the forensics.”

As to New Horizons, which will have an unmanned NASA spacecraft flyby Pluto in 2015, there are concerns that other, as yet undiscovered satellites may exist around the dwarf planet potentially posing a risk to the spacecraft.