The above image was taken just a day later than the one that revealed Pluto's big heart. On July 8, at 3.7 billion miles away from Pluto, NASA's New Horizons snapped the latest pic, capturing Pluto and its largest Moon Charon.
Charon is funny. It's huge -- at least compared to its host planet, which it's closer to in size than any other moon in the solar system is. And the pair doesn't really act like they're a moon and a host planet. Instead of orbiting around Pluto, Charon orbits around a spot next to Pluto -- and Pluto orbits that same spot. They're tidally locked, with the same side of Pluto always facing the same side of Charon, spinning around a fixed point while Pluto's smaller moons struggle to keep up.
But while they may be close, they don't seem to have much in common: Scientists have known for a while that Pluto is way brighter than Charon, and New Horizons' photos have only confirmed that.
In addition to being different colors -- Charon a moony gray and Pluto a reddish, peachy tan -- they also have different variations in their terrain. Pluto seems to have tons of different kinds of features -- that big dark whale, a big bright heart, and a series of dark spots, just to name the most prominent features waiting for closer observation.
Charon is expected to be interesting too -- probably pock-marked with craters -- but except for a dark region at the pole, it doesn't have much variation in reflectivity.
We can expect even better pictures of Pluto and Charon -- as well as some images of Nix, Styx, Kerberos and Hydra, Pluto's smaller moons -- in the coming days. And on July 14, New Horizons will zip past the Pluto system at 30,800 miles per hour and give us the front-row seat we've been waiting for.