A fuzzy Charon visible

Scientific American's Christopher Crockett wrote...

NASA’s New Horizons spacecraft, now en route to Pluto, got its first glimpse of the dwarf planet’s largest moon, Charon, in this image released July 10.

Pluto is the bright spot in the center of the image. Charon is the faint smudge up and to the left. New Horizons snapped the picture at about 900 million kilometers from Pluto—six times the distance between Earth and the sun. At that distance, the light from Charon and Pluto takes about 48 minutes to reach New Horizons’s cameras. Charon is roughly the size of Texas, but to the approaching craft it appears no wider than a U.S. quarter seen from 17 kilometers away

Until 2005 Charon was Pluto’s only known moon. Since then astronomers using the Hubble Space Telescope have discovered four more: Nix, Hydra, Kerberos and Styx. Kerberos and Styx are the smallest, each only about a dozen kilometers across; they received their official names just last week.

Launched in early 2006 New Horizons is scheduled to pass within 13,000 kilometers of Pluto in July 2015. The flyby will give astronomers their first close-up look at the tiny world and its moons. Mission scientists will study Pluto’s terrain, composition and atmosphere as well as the space environment in an unexplored, distant corner of the solar system. In the meantime, as New Horizons races toward Pluto, it will frequently snap photos of the dwarf planet’s surroundings to better understand the orbits of the known moons and to look out for potential hazards, such as smaller moonlets or a system of dusty rings.

Pluto belongs to a belt of icy debris beyond Neptune called the Kuiper Belt. Out there, much of the debris left over from the solar system’s formation sits in frozen storage. By studying Pluto and its moons, astronomers learn about more than a single world—they gain access to a record of our solar system’s birth and subsequent growth. In the end, Pluto may be able to tell us more about ourselves and how we got here.