The probe made contact to confirm its successful flyby of the icy Ultima Thule space rock, which is 19 miles wide and shaped like a giant peanut.
This marks a record for the most distant object to be explored.
New Horizon obtained gigabytes of photos and other observations which it will send home over the next few months.
Controllers at the Johns Hopkins University Applied Physics Laboratory in Maryland cheered and clapped as they received the signal.
Mission operations manager Alice Bowman said: “We have a healthy spacecraft. We’ve just accomplished the most distant flyby.”
Nasa administrator Jim Bridenstine said: “In addition to being the first to explore Pluto, today New Horizons flew by the most distant object ever visited by a spacecraft and became the first to directly explore an object that holds remnants from the birth of our solar system.
“This is what leadership in space exploration is all about.”
The radio message from the robotic craft was picked up in Madrid by one of Nasa’s big antennas. The data took six hours and eight minutes to traverse the massive breadth of space between Ultima and Earth.
According to Nasa, scientists had not discovered Ultima Thule when the probe was launched in 2006, meaning the mission was unique. In 2014, astronomers found Thule using the Hubble Space Telescope and selected it for New Horizon’s extended mission in 2015.
“Anything’s possible out there in this very unknown region,” said John Spencer, deputy project scientist for New Horizons.
Launched in January 2006, New Horizons embarked on a 4 billion mile journey towards the solar system’s frigid edge to study the dwarf planet Pluto and its five moons. The spacecraft, which is the size of a baby grand piano, flew past Pluto in 2015, providing the first close-up views of the planet.
During the flyby, the probe found Pluto to be slightly larger than previously thought. In March, it revealed that methane-rich dunes were on the icy dwarf planet’s surface.
After trekking 1 billion miles beyond Pluto into the Kuiper belt, New Horizons will now seek clues about the formation of the solar system and its planets.
There is a great deal scientists can learn from Ultima and the hundreds of thousands of similar bodies scientists deem to be in the solar system.
Hal Weaver, project scientist on the mission, told the BBC the rock is “probably the most primitive object ever encountered by a spacecraft, the best possible relic of the early solar system”.
The object is officially known as 2014 MU69, but was nicknamed Ultima Thule, a Latin phrase which means “beyond the borders of the known world”.
Additional reporting by Reuters
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