A multi-billion-kilometre flight, taking nine years to complete, has culminated in a major win for space science: the Pluto flyby.
The US probe shot past Pluto at 12.49pm UK time on a trajectory that brought the spacecraft within 12,500km of the body’s surface. The probe was travelling at 45,000 km/h (28,000 mph).
Nasa has released images of the team celebrating and with good reason – the US can now claim to have “visited” every planet in the classical solar system. More images will be released in the next four to five hours – because that's how long it takes for the images to travel back to earth.
“It should be a day of incredible pride,” said Charlie Bolden, Nasa’s chief administrator.
Over the debate around Pluto's planetary status, he added: “I call it a planet, but i’m not the rule-maker.”
The New Horizons probe set off on its mission in late 2005 – just months before Pluto was downgraded from planet to dwarf planet.
But it wasn't just the length of the journey, or the changing definition of the mission's subject, that was the problem.
New Horizons had to fly “a perfect path past Pluto, and with perfect timing” in order to get its momentous shot “otherwise its cameras will shoot empty sky where the dwarf or its moons are expected to be”.
This meant the probe had to remain within a keyhole” of space – 100km by 150 km (60 miles by 90 miles), and arrive at the location “within a set of margins of 100 seconds”.
Bolden said they were 72 seconds early, but Alan Stern said although it was “off centre” the probe was “well within spec”.
And because the good people of Nasa are so excellent, they conducted a Twitter Q&A.
We also enjoyed this comparison of Pluto with some kind of fried street food.