By Ian O’Neill
Published February 11, 2013
The artist’s concept shows some of the Pluto system from the surface of one of its moons, Nix. Pluto itself is the large disk at center, right. Charon is the smaller disk to the right of Pluto, Hydra the bright dot on Pluto’s far left. (NASA, ESA and G. Bacon (STScI))
The Plutonian system detailing the orbits of Charon, Nix, Hydra, “P4” and “P5.” (NASA)
Photos of far-off Pluto taken by the Hubble telescope aren’t sharp enough to see craters or mountains, if they exist on the surface, but Hubble reveals a complex-looking and variegated world with white, dark-orange, and charcoal-black terrain. (NASA, ESA, and M. Buie)
July 7, 2012: NASA’s Hubble Space Telescope has captured an image showing five moons orbiting the distant, icy dwarf planet Pluto. The green circle marks the newly discovered moon, designated P5. (NASA, ESA, and M. Showalter)
The moons of Pluto as scientists thought of them in 2006, when the Hubble telescope picked out the third and fourth moons. (NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI))
Pluto may have been demoted, but its family is getting bigger and bigger. Now, two of the dwarf planet’s tiniest moons need names — but rather than leaving the Plutonian satellites’ naming ceremony to astronomers, that honor has fallen to you.
The discoverers of Pluto’s smallest moons — measuring only 15 to 20 miles across — have designated the moons “P4″ and “P5,” but it’s about time that they grow up and get some real names. Discovered in 2011 and 2012 by the Hubble Space Telescope, this tiny duo joins Charon, Nix and Hydra in a very close-knit family of objects orbiting Pluto.
‘The Greeks were great storytellers and they have given us a colorful cast of characters to work with.’
– Mark Showalter, Senior Research Scientist at the Carl Sagan Center of the SETI Institute
All of the objects were named after Hades and the underworld in ancient Greek mythology. Hades, god of the underworld, who was also known as “Plouton” (meaning “Rich One”), was Latinized by the Romans to, simply, Pluto. And the ninth planetary body from the sun was given that name by 11-year old schoolgirl Venetia Burney shortly after the small world was discovered by Clyde Tombaugh at Lowell Observatory in 1930. The mythological name for the dark and cold world on the outskirts of the solar system has now been inherited by Pluto’s satellites.
So, the SETI Institute has launched a new website called “Pluto Rocks” to decide new names for P4 and P5. Of the possible mythological names, the following can be selected: Acheron, Alecto,Cerberus, Erebus, Eurydice, Hercules, Hypnos, Lethe, Obol, Orpheus, Persephone and Styx. You can also make your own suggestions.
“The Greeks were great storytellers and they have given us a colorful cast of characters to work with,” said Mark Showalter, Senior Research Scientist at the Carl Sagan Center of the SETI Institute in Mountain View, Calif., in a press release.
Voting will remain open till Feb. 25, when the P4/P5 discovery team will take the winning suggestions to the International Astronomical Union so the satellite pair can officially be named.
On Monday (Feb. 11) at 11 a.m., two astronomers involved in the P4/P5 discoveries — Mark Showalter and Hal Weaver, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland — will be available live to take your questions about the naming of these moons via a special Google+ hangout. If you want to get involved, be sure to use the #PlutoRocks hashtag on Twitter, the SETI Institute Facebook page and the Google hangout.
The naming of P4 and P5 may seem frivolous, but this more than a public outreach project. As NASA’s New Horizons probe flies through interplanetary space toward Pluto, in July 2015 the world will be awestruck by the first close-up photographs of dwarf planet Pluto and its largest companion Charon. The Plutonian moons will likely become household names (and the debate as to the planetary status of Pluto will likely be reignited).
But like any story from the underworld, there is a sinister back-story.
Last year, when Hubble spotted P4 and P5, concern mounted for the possibility of more, sub-resolution debris that may be hanging in Pluto orbit. The current plan for New Horizons is to fly straight between Pluto and Charon (only 6,200 miles from the surface of Pluto, pictured top), but if there’s a cloud (or ring) of debris or many smaller moonlets, there could be a substantial collision risk. This has prompted the NASA New Horizons Team — headed by Alan Stern — to formulate a “bale out” plan should the risk be deemed too great. This means mission managers may opt to command New Horizons to carry out its much anticipated flyby further away from Pluto and any potential dangers that lay in wait.
So, for now, astronomers are carefully surveying the volume of space around Pluto, looking for any hint of the hypothetical debris that may be hiding there.