January 21, 2016 – After its close approach to Pluto, the New Horizons spacecraft snapped this hauntingly beautiful image of the night side of Pluto’s largest moon, Charon.
Only an imager on the far side of Pluto could catch such a view, with a bright, thin sliver of Charon near the lower left illuminated by the sun. Night has fallen over the rest of this side of Charon, yet despite the lack of sunlight over most of the surface, Charon’s nighttime landscapes are still faintly visible by light softly reflected off Pluto, just as “Earthshine” lights up a new moon each month. Charon is 750 miles (1,214 kilometers) in diameter, approximately as wide as Texas.
Scientists on the New Horizons team are using this and similar images to map portions of Charon otherwise not visible during the flyby. This includes Charon’s south pole – toward the top of this image – which entered polar night in 1989 and will not see sunlight again until 2107. Charon’s polar temperatures drop to near absolute zero during this long winter.
This combination of 16 one-second exposures was taken by New Horizons’ Long Range Reconnaissance Imager (LORRI) at 2:30 UT on July 17, 2015, nearly three days after closest approach to Pluto and Charon, from a range of 1.9 million miles (3.1 million kilometers).