LAUREL, Maryland, July 9 — It began as a faint speck in Hubble Space Telescope images back in 2014, just another distant point of light in the outer darkness. Now, more than a decade later, scientists are still unpacking what that speck taught us about the very dawn of the solar system. New Horizons, the spacecraft that gave humanity its first close look at Pluto, kept going.
On January 1, 2019, it flew past an object originally designated 2014 MU69, later named Arrokoth. The encounter happened about 2,200 miles from the surface, revealing something no one had quite seen before: a contact binary, two distinct lobes gently pressed together, stretching 22 miles end to end.
What makes Arrokoth special isn’t its shape, though that is striking. It is one of the most primitive objects ever observed, a relic from the early solar system that has remained largely unchanged for billions of years. For the team behind New Horizons, this was the payoff of a journey that began long before Arrokoth was even discovered.
A Journey Across Decades
The spacecraft launched on January 19, 2006, riding an Atlas V rocket into a trajectory that would take it past Jupiter for a gravity assist on February 28, 2007. That planetary slingshot sent New Horizons racing toward its primary target: Pluto. On July 14, 2015, the probe passed within 7,800 miles of Pluto’s surface.
The images that came back stunned the world. There was the heart-shaped Sputnik Planitia, vast plains of nitrogen ice.
Water ice mountains rose from the surface. Glaciers flowed across the dwarf planet, revealing a world far more dynamic than anyone had predicted. But Pluto was never meant to be the end of the road.
The spacecraft kept its power, kept its course, and the team searched for a new destination. Hubble found it in 2014: a tiny Kuiper Belt object, barely visible, that would become Arrokoth.
What Arrokoth Reveals
The flyby on New Year’s Day 2019 showed a world that looks almost untouched by time. As a contact binary, Arrokoth appears to have formed when two separate bodies gently came together in the early solar system, merging into a single object without the violent collisions that shaped larger worlds. For researchers studying how planets form, Arrokoth is a time capsule.
It preserves conditions from the solar system’s infancy, offering clues about the processes that built everything from asteroids to Earth itself. The data from that brief flyby continues to yield insights years later.
The spacecraft itself is still out there, still operating. Its radioisotope thermoelectric generator, or RTG, provides power that is expected to last until the late 2030s. That gives scientists years more to gather data as New Horizons pushes deeper into the outer solar system.
What Comes Next
New Horizons is now on a trajectory to exit the heliosphere in the nose region, the direction the solar system is moving through interstellar space. The spacecraft is expected to cross the heliopause, the boundary where the Sun’s influence gives way to the galaxy beyond, sometime in the 2040s. That will make New Horizons only the fifth human-made object to leave the heliosphere, following Voyager 1 and Voyager 2, and eventually Pioneers 10 and 11.
Each crossing provides a different perspective on the bubble our Sun creates around itself. For now, the spacecraft continues its lonely journey, sending back data from a region of space most of humanity will never see.
Arrokoth recedes in the distance, a frozen remnant of the beginning, while New Horizons pushes toward the edge.
