The nuclear-powered unmanned probe sped past the dwarf planet at a distance of 12,500 km (7,750 mi) and a speed of 14 km/sec (31,000 mph), making it the final classical planet to be visited by a spacecraft.

The New Horizons flyby is not only historic, but also a bit paradoxical. Because the US$750 million spacecraft is on a ballistic trajectory, NASA mission control is in no doubt that it has flown past Pluto. The question is, did it survive the attempt and what is its present status? Because Pluto is currently 4.77 billion km (2.97 billion mi) from Earth, radio signals from New Horizons take 4 hr and 25 min to reach us.

Worse, during the flyby, New Horizons is positioning itself to bring its suite of seven scientific instruments to bear, so the probe's main antenna isn't pointing in the right direction to transmit to NASA's Deep Space Network on Earth. According to NASA, this means that news of the mission's success or failure will not be received until about 9:00 pm EDT.