Temporarily assigned the name “P4,” the new moon joins Charon, Hydra and Nix as the fourth member of Pluto’s satellites. P4 is the smallest of Pluto’s moons, with a diameter of only 8-21 ...

Following the spacecraft's big revelation of just how enormous Pluto's moon Charon was in 2013, New Horizons is now within sight of all the known members of the Pluto system, according to NASA.

A fourth moon has been discovered in its orbit, not an easy thing to do because Pluto is not only the furthest planet from the Earth, but also has an elliptical (read "crazy") orbit. Yeah, we said it.

Charon, Pluto's largest moon, is nearly as massive as Pluto; they are often called a "double planet" (though neither meets the criteria for a planet). Charon could potentially keep Pluto warm, if the ...

Their pairing with the moon on July 20 creates a picturesque scene, especially when viewed through binoculars, which frame the glittering stars and glowing crescent in the same field of view. Pluto at ...