New Pluto Moon Found—"Fringe Benefit" of Search for Risky Rings
Unnamed natural satellite underscores Pluto's surprising complexity.
Finding the new moon this summer was a "fringe benefit" of a monthlong program to scan Pluto for rocky rings that could endanger NASA's New Horizons spacecraft, said planetary astronomer Mark Showalter, who's leading the Hubble scanning project. The probe is to fly by the dwarf planet in July 2015.
(Related: "New Pluto Pictures Unveiled; Hubble's Sharpest Yet.")
Even in the Hubble's best images, the new moon—some 3.7 billion miles (5.9 billion) miles from the sun—is visible only as a speck of light.
Based on its brightness, the temporarily named P5 is probably 6 to 15 miles (10 to 25 kilometers) in diameter—about two-thirds the size of P4, the Plutonian moon discovered in 2011.
The new moon adds one