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More Moons Over Pluto? 
New Horizons Mission News
February 24, 2003

Pluto has only one known satellite - Charon - discovered in 1978 by
American astronomer James Christy. At slightly more than half the 
diameter of Pluto, Charon's 1,200-kilometer diameter makes it the 
undisputed "relative size" king of solar system satellites. In fact, 
Charon is so big compared to Pluto that the system's center of mass 
actually falls between the two bodies, making Pluto-Charon the only 
true binary planet in the solar system.

Recently, astronomers have discovered that some large Kuiper Belt 
Objects also have large satellites. This, combined with the fact that 
previous searches for satellites around Pluto could have missed moons 
as large as hundreds of kilometers across, suggests to the New 
Horizons mission team that Pluto might have other, as-yet undiscovered 
satellites. 

"Discovering another moon or moons around Pluto-Charon would be
exciting in and of itself, and could tell us a lot about the dynamical 
evolution of this unique, binary system," says New Horizons Principal 
Investigator Dr. Alan Stern of the Southwest Research Institute Space 
Studies Department, Boulder, Colo. "Whether or not we find new moons 
of Pluto, we expect to learn more about how and where Kuiper Belt 
satellites form. And, of course, any discoveries of new moons of Pluto 
would become targets of interest for the New Horizons flyby of the 
Pluto-Charon system."

Therefore, the New Horizons project is organizing a search for 
additional satellites of Pluto. "It's something we plan to complete 
relatively quickly - that is, this year," says Dr. Harold Weaver, New 
Horizons deputy project scientist from The Johns Hopkins University 
Applied Physics Laboratory, Laurel, Md. "We will use both ground-based 
telescopes and, we hope, the Hubble Space Telescope." 

"With modern tools we should be able to determine if Pluto has any
satellites larger than perhaps 10 or 20 kilometers across," Stern 
adds, "and do so with only a few days of telescope observing time."

"The prospect that Pluto might have one or more, possibly even many
satellites lurking about it is intriguing," Weaver says. "It is also 
important to know just how many satellites are in the system as part 
of our detailed mission planning activities." 

http://pluto.jhuapl.edu/022403.htm

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