Photos: Delta 4-Heavy launch gallery

There is no sign of an undiscovered moon lurking around Pluto in data streaming back to Earth from NASA’s New Horizons spacecraft, and that is surprising to Alan Stern, the scientist in charge of the probe.

Three years and a billion miles past Pluto, NASA’s New Horizons probe is on the verge of at least one more pioneering, once-in-a-lifetime milestone: a New Year’s Day flyby of a small body known as 2014 MU69, unofficially dubbed Ultima Thule — “beyond the known world” — in a NASA naming contest.